MERGED-(Fresh opti pull pics) & (Ignition stutter-Code crackers needed)
08-10-2008, 11:58 PM
#181
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From an article that B Cunningham linked (excellent article!)
Understanding and Modifying This Much-Maligned Ignition System
Way back in March of 1998, GMHTP ran "Opti-Spark" by Ray Bohacz, an engineering-level dissection of GM's Opti-Spark distributor. This evolutionary ignition component was a bridge between traditional distributors and the DIS-type, coil-on-plug systems that we know and love today. Unfortunately, LT1 owners have had long-term reliability problems with the Opti-Spark, and even though it has been around for 11 years now, many enthusiasts are still in the dark when it comes to identifying, troubleshooting, or upgrading them. The first half of this story is a similar version of the one Ray wrote in 1998; the last half focuses on model identification, trouble signs, and new technology that will allow Optis to last longer and perform better.
To be worthy of the famous LT1 designation the latest rendition of this engine needed to exceed the pre-emissions version's power generation while meeting today's demanding standards to be considered world-class. Specific mass, size, fuel consumption, emissions, start-ability and torque-band-width all needed to be improved over the L98 engine that it replaced--all while surpassing previous reliability levels.
Early on in the LT1's development the design team recognized the inherent deficiencies of the then-current L98 and the pitfalls it would cause in arriving at their goals. To this cause the LT1 employed advanced theories such as reverse-flow engine cooling and a gear-driven water pump. The Opti-Spark first appeared on the 1992 Corvette and then progressed to the fourth-generation F-body in 1993. The same ignition is also found in the full-size B-body cars when they switched to LT1 power for the 1994 model year. During the Opti-Spark's reign there were three distinct versions of the distributor, but they all functioned in the same manner. The differences were found in the drive mechanism along with the design of the housing and vent system.
Time Versus Angle-Based Ignition
Prior to the Opti-Spark most conventional ignition systems referenced the delivery of the spark through a time-based method. These systems functioned on a prescribed time-delay period after passing a reference point that was usually an interrupt signal from a magnetic reluctance sensor, more commonly known as a pick-up coil. In contrast, the Opti-Spark uses multiple optical sensors working in conjunction with a two-track slotted disk to have the ability to identify in one-degree increments the position of the crankshaft. This is done by incorporating both a high-resolution outer track of 360 slots and a low-resolution inner track with eight varying-width slots that identify each cylinder.
By recognizing both the leading and falling edges of the high-resolution signal, the ECM knows the position of the crankshaft within one degree. A light beam is created by dual LEDs and photo transistors and reads the low-resolution slot signals at TDC for each cylinder. The number of high-resolution pulses observed prior to reaching the falling edge of a low-resolution slot is the method used for identification. The light passing through each of the slots generates a 5-volt transistor-to-transistor logic signal that is recognized by the ECM.
Using both the leading and falling, commonly referred to as the trailing edge of the square wave output generated by the high-resolution sensor, effectively encodes 720 high-resolution edges to keep track of the crankshaft's position in lieu of the four acknowledged positions that a conventional ignition is referenced from. By comparison, a magnetic reluctance sensor (unless equipped with an ancillary signature pulse) has no knowledge of which cylinder is firing. But more importantly, it has 45 degrees of distributor rotation that is not recognized and is unaccountable.
The Opti-Spark ignition system breaks tradition in a number of unique ways beyond its optical triggers. The following technology is represented in this design:
The combination of two systems in one. A high-resolution engine timing system and a low-energy secondary distribution network.
The ability for the ECM to have total control over the ignition timing through an angle-based spark advance function along with the ancillary control of altering the cranking start-up ignition timing based on the ambient air temperature.
Robust reductions in spark scatter during instantaneous transient acceleration of 10-rpm-per-millisecond or greater intervals in comparison with time-based methodology.
The ability to benefit from a more aggressive timing curve without entering the spark knock zone.
A large cap design with a widened rotor tip, allowing for all of the secondary voltage to be delivered radially without employing a large rotor tip clearance. This reduction in rotor tip clearance also pays dividends in decreased radio frequency interference generation.
Individual cylinder timing and knock retard capabilities.
Accurate drive positioning directly from the front of the camshaft.
No need for mechanical timing adjustment.
Way back in March of 1998, GMHTP ran "Opti-Spark" by Ray Bohacz, an engineering-level dissection of GM's Opti-Spark distributor. This evolutionary ignition component was a bridge between traditional distributors and the DIS-type, coil-on-plug systems that we know and love today. Unfortunately, LT1 owners have had long-term reliability problems with the Opti-Spark, and even though it has been around for 11 years now, many enthusiasts are still in the dark when it comes to identifying, troubleshooting, or upgrading them. The first half of this story is a similar version of the one Ray wrote in 1998; the last half focuses on model identification, trouble signs, and new technology that will allow Optis to last longer and perform better.
To be worthy of the famous LT1 designation the latest rendition of this engine needed to exceed the pre-emissions version's power generation while meeting today's demanding standards to be considered world-class. Specific mass, size, fuel consumption, emissions, start-ability and torque-band-width all needed to be improved over the L98 engine that it replaced--all while surpassing previous reliability levels.
Early on in the LT1's development the design team recognized the inherent deficiencies of the then-current L98 and the pitfalls it would cause in arriving at their goals. To this cause the LT1 employed advanced theories such as reverse-flow engine cooling and a gear-driven water pump. The Opti-Spark first appeared on the 1992 Corvette and then progressed to the fourth-generation F-body in 1993. The same ignition is also found in the full-size B-body cars when they switched to LT1 power for the 1994 model year. During the Opti-Spark's reign there were three distinct versions of the distributor, but they all functioned in the same manner. The differences were found in the drive mechanism along with the design of the housing and vent system.
Time Versus Angle-Based Ignition
Prior to the Opti-Spark most conventional ignition systems referenced the delivery of the spark through a time-based method. These systems functioned on a prescribed time-delay period after passing a reference point that was usually an interrupt signal from a magnetic reluctance sensor, more commonly known as a pick-up coil. In contrast, the Opti-Spark uses multiple optical sensors working in conjunction with a two-track slotted disk to have the ability to identify in one-degree increments the position of the crankshaft. This is done by incorporating both a high-resolution outer track of 360 slots and a low-resolution inner track with eight varying-width slots that identify each cylinder.
By recognizing both the leading and falling edges of the high-resolution signal, the ECM knows the position of the crankshaft within one degree. A light beam is created by dual LEDs and photo transistors and reads the low-resolution slot signals at TDC for each cylinder. The number of high-resolution pulses observed prior to reaching the falling edge of a low-resolution slot is the method used for identification. The light passing through each of the slots generates a 5-volt transistor-to-transistor logic signal that is recognized by the ECM.
Using both the leading and falling, commonly referred to as the trailing edge of the square wave output generated by the high-resolution sensor, effectively encodes 720 high-resolution edges to keep track of the crankshaft's position in lieu of the four acknowledged positions that a conventional ignition is referenced from. By comparison, a magnetic reluctance sensor (unless equipped with an ancillary signature pulse) has no knowledge of which cylinder is firing. But more importantly, it has 45 degrees of distributor rotation that is not recognized and is unaccountable.
The Opti-Spark ignition system breaks tradition in a number of unique ways beyond its optical triggers. The following technology is represented in this design:
The combination of two systems in one. A high-resolution engine timing system and a low-energy secondary distribution network.
The ability for the ECM to have total control over the ignition timing through an angle-based spark advance function along with the ancillary control of altering the cranking start-up ignition timing based on the ambient air temperature.
Robust reductions in spark scatter during instantaneous transient acceleration of 10-rpm-per-millisecond or greater intervals in comparison with time-based methodology.
The ability to benefit from a more aggressive timing curve without entering the spark knock zone.
A large cap design with a widened rotor tip, allowing for all of the secondary voltage to be delivered radially without employing a large rotor tip clearance. This reduction in rotor tip clearance also pays dividends in decreased radio frequency interference generation.
Individual cylinder timing and knock retard capabilities.
Accurate drive positioning directly from the front of the camshaft.
No need for mechanical timing adjustment.
08-11-2008, 12:32 AM
#182
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more from the opti link with my highlights...
With my ICC DTC 41 fault, the answer is in here somewhere...
Opti-Spark Features
The LT1 ignition system could actually be referred to as a hybrid that is a cross between a time-based conventional ignition and a corresponding duration-configured distributorless design. Prior to the development of the Opti-Spark the exact position of the crankshaft was never recognized by the ECM, that data was not available. The input of data in one-degree increments of crankshaft rotation into the ECM's programming now allows for more accurate control of engine functions. In a standard L98 ignition, which is an electronic-spark-timing high-energy system, control of the spark advance curve is handled by the tables in the PROM once an engine speed of 400 rpm was surpassed. Below that rpm the control of the ignition timing was independent of the ECM and was a function of the module and the installed position of the distributor. Testing by GM proved that at an ambient temperature of -35 degrees C, the time-based ignition would have a start time of approximately four seconds while the angle-based LT1 would fire in 1.5 seconds. This is the result of knowing the exact crankshaft position along with the ability to vary the ignition timing on crank as a function of coolant temperature.
To a calibration engineer concerned with meeting EPA cold-start emissions standards this is invaluable. When the engine is craOpti-Spark Features
The LT1 ignition system could actually be referred to as a hybrid that is a cross between a time-based conventional ignition and a corresponding duration-configured distributorless design. Prior to the development of the Opti-Spark the exact position of the crankshaft was never recognized by the ECM, that data was not available. The input of data in one-degree increments of crankshaft rotation into the ECM's programming now allows for more accurate control of engine functions. In a standard L98 ignition, which is an electronic-spark-timing high-energy system, control of the spark advance curve is handled by the tables in the PROM once an engine speed of 400 rpm was surpassed. Below that rpm the control of the ignition timing was independent of the ECM and was a function of the module and the installed position of the distributor. Testing by GM proved that at an ambient temperature of -35 degrees C, the time-based ignition would have a start time of approximately four seconds while the angle-based LT1 would fire in 1.5 seconds. This is the result of knowing the exact crankshaft position along with the ability to vary the ignition timing on crank as a function of coolant temperature.
To a calibration engineer concerned with meeting EPA cold-start emissions standards this is invaluable. When the engine is cranking, fuel is being administered at a rate of inject pulses twice as often as it is during engine run along with substantially longer pulse widths. The more fuel injected during crank, the higher the hydrocarbon emissions and the longer it will take the catalytic converter to light off once combustion starts. By decreasing the cold start crank time, the extremely critical first two minutes of emissions output is greatly reduced. This is a major concern during the EPA cold start test cycle.
A combination of a decreased rotor gap, along with the use of a conductive ink to route the spark path in the plastic encapsulated distributor cap, allows for minimal voltage losses and longer burn times at the plug from the increased available energy. Burn times are referenced in degrees of crankshaft rotation that the ignition system has the ability to keep the spark plug ignited. Any gains are extremely desirable and increase the conversion of chemical to mechanical energy. Energy losses that are absorbed by the larger necessary rotor gap in a conventional distributor consumes a portion of the coil's output, leaving less voltage to bridge the gap of the spark plug.nking, fuel is being administered at a rate of inject pulses twice as often as it is during engine run along with substantially longer pulse widths. The more fuel injected during crank, the higher the hydrocarbon emissions and the longer it will take the catalytic converter to light off once combustion starts. By decreasing the cold start crank time, the extremely critical first two minutes of emissions output is greatly reduced. This is a major concern during the EPA cold start test cycle.
A combination of a decreased rotor gap, along with the use of a conductive ink to route the spark path in the plastic encapsulated distributor cap, allows for minimal voltage losses and longer burn times at the plug from the increased available energy. Burn times are referenced in degrees of crankshaft rotation that the ignition system has the ability to keep the spark plug ignited. Any gains are extremely desirable and increase the conversion of chemical to mechanical energy. Energy losses that are absorbed by the larger necessary rotor gap in a conventional distributor consumes a portion of the coil's output, leaving less voltage to bridge the gap of the spark plug.
Opti-Spark Features
The LT1 ignition system could actually be referred to as a hybrid that is a cross between a time-based conventional ignition and a corresponding duration-configured distributorless design. Prior to the development of the Opti-Spark the exact position of the crankshaft was never recognized by the ECM, that data was not available. The input of data in one-degree increments of crankshaft rotation into the ECM's programming now allows for more accurate control of engine functions. In a standard L98 ignition, which is an electronic-spark-timing high-energy system, control of the spark advance curve is handled by the tables in the PROM once an engine speed of 400 rpm was surpassed. Below that rpm the control of the ignition timing was independent of the ECM and was a function of the module and the installed position of the distributor. Testing by GM proved that at an ambient temperature of -35 degrees C, the time-based ignition would have a start time of approximately four seconds while the angle-based LT1 would fire in 1.5 seconds. This is the result of knowing the exact crankshaft position along with the ability to vary the ignition timing on crank as a function of coolant temperature.
To a calibration engineer concerned with meeting EPA cold-start emissions standards this is invaluable. When the engine is craOpti-Spark Features
The LT1 ignition system could actually be referred to as a hybrid that is a cross between a time-based conventional ignition and a corresponding duration-configured distributorless design. Prior to the development of the Opti-Spark the exact position of the crankshaft was never recognized by the ECM, that data was not available. The input of data in one-degree increments of crankshaft rotation into the ECM's programming now allows for more accurate control of engine functions. In a standard L98 ignition, which is an electronic-spark-timing high-energy system, control of the spark advance curve is handled by the tables in the PROM once an engine speed of 400 rpm was surpassed. Below that rpm the control of the ignition timing was independent of the ECM and was a function of the module and the installed position of the distributor. Testing by GM proved that at an ambient temperature of -35 degrees C, the time-based ignition would have a start time of approximately four seconds while the angle-based LT1 would fire in 1.5 seconds. This is the result of knowing the exact crankshaft position along with the ability to vary the ignition timing on crank as a function of coolant temperature.
To a calibration engineer concerned with meeting EPA cold-start emissions standards this is invaluable. When the engine is cranking, fuel is being administered at a rate of inject pulses twice as often as it is during engine run along with substantially longer pulse widths. The more fuel injected during crank, the higher the hydrocarbon emissions and the longer it will take the catalytic converter to light off once combustion starts. By decreasing the cold start crank time, the extremely critical first two minutes of emissions output is greatly reduced. This is a major concern during the EPA cold start test cycle.
A combination of a decreased rotor gap, along with the use of a conductive ink to route the spark path in the plastic encapsulated distributor cap, allows for minimal voltage losses and longer burn times at the plug from the increased available energy. Burn times are referenced in degrees of crankshaft rotation that the ignition system has the ability to keep the spark plug ignited. Any gains are extremely desirable and increase the conversion of chemical to mechanical energy. Energy losses that are absorbed by the larger necessary rotor gap in a conventional distributor consumes a portion of the coil's output, leaving less voltage to bridge the gap of the spark plug.nking, fuel is being administered at a rate of inject pulses twice as often as it is during engine run along with substantially longer pulse widths. The more fuel injected during crank, the higher the hydrocarbon emissions and the longer it will take the catalytic converter to light off once combustion starts. By decreasing the cold start crank time, the extremely critical first two minutes of emissions output is greatly reduced. This is a major concern during the EPA cold start test cycle.
A combination of a decreased rotor gap, along with the use of a conductive ink to route the spark path in the plastic encapsulated distributor cap, allows for minimal voltage losses and longer burn times at the plug from the increased available energy. Burn times are referenced in degrees of crankshaft rotation that the ignition system has the ability to keep the spark plug ignited. Any gains are extremely desirable and increase the conversion of chemical to mechanical energy. Energy losses that are absorbed by the larger necessary rotor gap in a conventional distributor consumes a portion of the coil's output, leaving less voltage to bridge the gap of the spark plug.
08-11-2008, 02:09 AM
#183
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A few more leads to follow through on with my ICC fault: (look for comparable symptoms with low-rpm sputter)...
To eliminate this problem, later designs incorporated a more efficient venting system that pulled air through the distributor housing from the throttle body. This was supposed to eliminate once and for all the moisture issue.
Other changes were made over the years to the engine-side of the housing and the size and attachment of the drive mechanism. Due to this there are three different timing case covers used on LT1 engines. Abe Bergian, motorsports service manager at Jay Fisher Pontiac-GMC, explained that the 1992 to 1994 versions of the Opti-Spark on both F- and Y-cars had no vent and used the timing case cover with a small distributor drive hole. 1994 B-cars used a new timing case and companion Opti-Spark that had increased venting, a serviceable cap and rotor, and a new-style drive attachment to the camshaft. This style was then switched to the F- and Y-cars for the 1995 model year. With the arrival of OBD-II for 1996, the timing case was again modified to accept a crankshaft sensor for misfire diagnostics but the Opti-Spark was unchanged. The older-style unvented design can be updated to the final version but would require a new-style timing case, Opti-Spark distributor, and changes to the cam drive mechanism. In addition, a longer dowel pin needs to be installed in the camshaft to drive the distributor. The first iteration used a traditional short Chevrolet cam dowel pin.
To eliminate this problem, later designs incorporated a more efficient venting system that pulled air through the distributor housing from the throttle body. This was supposed to eliminate once and for all the moisture issue.
Other changes were made over the years to the engine-side of the housing and the size and attachment of the drive mechanism. Due to this there are three different timing case covers used on LT1 engines. Abe Bergian, motorsports service manager at Jay Fisher Pontiac-GMC, explained that the 1992 to 1994 versions of the Opti-Spark on both F- and Y-cars had no vent and used the timing case cover with a small distributor drive hole. 1994 B-cars used a new timing case and companion Opti-Spark that had increased venting, a serviceable cap and rotor, and a new-style drive attachment to the camshaft. This style was then switched to the F- and Y-cars for the 1995 model year. With the arrival of OBD-II for 1996, the timing case was again modified to accept a crankshaft sensor for misfire diagnostics but the Opti-Spark was unchanged. The older-style unvented design can be updated to the final version but would require a new-style timing case, Opti-Spark distributor, and changes to the cam drive mechanism. In addition, a longer dowel pin needs to be installed in the camshaft to drive the distributor. The first iteration used a traditional short Chevrolet cam dowel pin.
08-11-2008, 05:42 AM
#185
Melting Slicks
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oh man.. sorry to hear about all this Schrade, you seem like a good guy, and this is one serious PITA.
Sorry I have no experience at all with any of the probs your having, I would love to be able to help haha.
Next time your in Florida we will get drunk and cuss at it till it works.
Sorry I have no experience at all with any of the probs your having, I would love to be able to help haha.
Next time your in Florida we will get drunk and cuss at it till it works.
08-15-2008, 09:06 PM
#186
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Guys I hope all is well for you. I just received my new computer and put it in car and my car runs better than when I bought it. It is so smooth and idles like a new car. I wish the best to you guys and hopefully mine is fixed.....
08-16-2008, 12:02 AM
#187
Melting Slicks
Just in case you are wondering, here is the continuation of this thread:
http://www.digitalcorvettes.com/foru...d.php?t=106692
I think he is gettin' close, or at least I hope he is!
I'll update the thread when he figures out whats going on in there.
http://www.digitalcorvettes.com/foru...d.php?t=106692
I think he is gettin' close, or at least I hope he is!
I'll update the thread when he figures out whats going on in there.
08-16-2008, 11:36 PM
#188
Melting Slicks
More inspection today reveals the presence of Mice in the past...lot of work to be done yet, but the pieces seem to be falling together.
http://www.digitalcorvettes.com/foru...d.php?t=106950
Looks like the dash will be coming out with inspection of many wires to follow.
http://www.digitalcorvettes.com/foru...d.php?t=106950
Looks like the dash will be coming out with inspection of many wires to follow.
08-20-2008, 07:27 PM
#189
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Well it made it 5 days on new ECM.....Starting running rough and throwing codes today. 1) H-41, 4) H-51, 9) H-64, and H-72. Yesterday I replaced all seals on my A/C again and could not get my compressor to turn on. I wiggled and plugged and unplugged the low pressure switch and the fans came on and so did the a/c. Today when it was throwing codes it would do it everytime I hit a hard bump. I think I have a faulty wire on the a/c circuit at that plug. Does anyone have any advice on this? Replace that switch and plug? Last time I found 2 of the wires touching and it made the car start. This was the same 2 wires on the low pressure switch then too.
08-21-2008, 10:27 PM
#190
Melting Slicks
Good news, progress has been made. VSS DTC eliminated, loose connection was the cause.
Here's the link to the continuation:
http://www.digitalcorvettes.com/foru...=106692&page=4
Here's the link to the continuation:
http://www.digitalcorvettes.com/foru...=106692&page=4
09-07-2010, 08:24 AM
#192
Instructor
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Helo-o-o-o-o-o??? Blast from the past here...
I ended up driving my disabled Vette most of early 2009 and putting it up on jacks at the end of Summer that year. Only recently did I rip it apart:
- New Pacesetter shorty headers (my cast-iron exhaust manifolds were CRACKED!!!)
- New water pump
- Reman Opti (Cardone speshial from Advance Auto for $110)
- New knock sensors, coolant temp sensor
- AIR/EGR delete plates.
- various gaskets, hoses, belt, pulleys.
The Cardone Opti was a MASSIVE PIECE OF... it didn't work out of the box so I just cleaned up my old Opti and put it back on (since I was using my DelTeq system anyway for spark.)
Unfortunately, while the car runs well otherwise, the problem remains. I did a few tests and feel 99.9% sure it has something to do with the computer and electric radiator fan. Essentially, when the fans kick on (due to A/C compressor turning on or them coming on at 205*F to help cool) the engine momentarily lopes in it's idle, a CEL comes on, and the engine sounds like timing is pulled way back. It still runs and drives well, but the exhaust note is considerably noisier and the CEL stays on. Also, acceleration is a little sluggish.
So, could this be a fried PCM? Bad electric fan? Bad fan relays...or bad wiring? Again, any help would be appreciated.
I ended up driving my disabled Vette most of early 2009 and putting it up on jacks at the end of Summer that year. Only recently did I rip it apart:
- New Pacesetter shorty headers (my cast-iron exhaust manifolds were CRACKED!!!)
- New water pump
- Reman Opti (Cardone speshial from Advance Auto for $110)
- New knock sensors, coolant temp sensor
- AIR/EGR delete plates.
- various gaskets, hoses, belt, pulleys.
The Cardone Opti was a MASSIVE PIECE OF... it didn't work out of the box so I just cleaned up my old Opti and put it back on (since I was using my DelTeq system anyway for spark.)
Unfortunately, while the car runs well otherwise, the problem remains. I did a few tests and feel 99.9% sure it has something to do with the computer and electric radiator fan. Essentially, when the fans kick on (due to A/C compressor turning on or them coming on at 205*F to help cool) the engine momentarily lopes in it's idle, a CEL comes on, and the engine sounds like timing is pulled way back. It still runs and drives well, but the exhaust note is considerably noisier and the CEL stays on. Also, acceleration is a little sluggish.
So, could this be a fried PCM? Bad electric fan? Bad fan relays...or bad wiring? Again, any help would be appreciated.
09-07-2010, 09:30 AM
#193
Le Mans Master
There is a set of wires from the opti to the passenger intake connector. Sometimes it will ohm correctly, but when hot will stop working.
Another member had a similar issue and sent thier ECM off to repair and it fixed their problem until the ICM took a dump. You don't have an ICM so it can't be that.
Good luck
Another member had a similar issue and sent thier ECM off to repair and it fixed their problem until the ICM took a dump. You don't have an ICM so it can't be that.
Good luck
09-07-2010, 05:33 PM
#194
Instructor
Yes, he does have an ICM. It's a '95.
Is your battery and alternator strong ? When your compressor/fan turn on, there is a high instantaneous current demand which may be pulling your Bat/Alt source voltage under 9V.
Also, check for error codes. Paper clip, short ALDL #4 and #12 method.
Is your battery and alternator strong ? When your compressor/fan turn on, there is a high instantaneous current demand which may be pulling your Bat/Alt source voltage under 9V.
Also, check for error codes. Paper clip, short ALDL #4 and #12 method.
09-07-2010, 08:56 PM
#195
Burning Brakes
I don't think so Al!
Sorry.... I had to.
Even though he has a 95 he has the Delteq kit installed which replaces the ICM and some other things as well. He is also very well versed in code retrival.
zeitgeist57 - I have been reading this thread with great anticipation. I have a 92 with the Delteq kit and a bad miss (studder, hesitation, shunt, whatever you want to call it) that starts at high engine speeds but will come down as the engine gets hotter (or stays at normal running temps for long drives, my engine temps hang at 190 on the road). I already replaced the coil module (under the coils) after it tested bad at Advance. I am nearly convinced my problem is a coil but I got one (didn't want to do them all without knowing for sure that they are the problem) and tried it in all four locations. The problem persisted. After reading all of this I think I will try my spare ECM to see if it changes anything. It has a datalink issue but runs the engine well. If that doesn't fix it I think I might buy three more coils.
Also, I am logging data on my test runs. I am seeing some knock retard timing at higher speeds and when the shunt happens so I have moved to running Sunoco 93 and will probably stick with it. It is a nice gesture but hasn't fixed the problem. All of my other data seems to be ok.
To fix something like this you need data! A factory service manual is pretty much required too.
Have you contacted Delteq about your problem yet? I am going to try to get them tomorrow.
Note: One big difference I have is that I am not getting any codes associated with this failure.
Matt
Sorry.... I had to.
Even though he has a 95 he has the Delteq kit installed which replaces the ICM and some other things as well. He is also very well versed in code retrival.
zeitgeist57 - I have been reading this thread with great anticipation. I have a 92 with the Delteq kit and a bad miss (studder, hesitation, shunt, whatever you want to call it) that starts at high engine speeds but will come down as the engine gets hotter (or stays at normal running temps for long drives, my engine temps hang at 190 on the road). I already replaced the coil module (under the coils) after it tested bad at Advance. I am nearly convinced my problem is a coil but I got one (didn't want to do them all without knowing for sure that they are the problem) and tried it in all four locations. The problem persisted. After reading all of this I think I will try my spare ECM to see if it changes anything. It has a datalink issue but runs the engine well. If that doesn't fix it I think I might buy three more coils.
Also, I am logging data on my test runs. I am seeing some knock retard timing at higher speeds and when the shunt happens so I have moved to running Sunoco 93 and will probably stick with it. It is a nice gesture but hasn't fixed the problem. All of my other data seems to be ok.
To fix something like this you need data! A factory service manual is pretty much required too.
Have you contacted Delteq about your problem yet? I am going to try to get them tomorrow.
Note: One big difference I have is that I am not getting any codes associated with this failure.
Matt
09-08-2010, 12:07 AM
#196
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I consistently get codes H41, H42.
DelTeq has fallen off the face of the earth?
If I did get a new ECM...is the Chevy dealership the only place that can reflash it? What if I want a tuner to update it?
DelTeq has fallen off the face of the earth?
If I did get a new ECM...is the Chevy dealership the only place that can reflash it? What if I want a tuner to update it?
09-08-2010, 12:45 AM
#197
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I am nearly convinced my problem is a coil but I got one (didn't want to do them all without knowing for sure that they are the problem) and tried it in all four locations. The problem persisted. After reading all of this I think I will try my spare ECM to see if it changes anything. It has a datalink issue but runs the engine well. If that doesn't fix it I think I might buy three more coils.
Note: One big difference I have is that I am not getting any codes associated with this failure.
Matt
Note: One big difference I have is that I am not getting any codes associated with this failure.
Matt
09-08-2010, 12:48 AM
#198
Racer
Member Since: Apr 2010
Location: New York
Posts: 409
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Well it made it 5 days on new ECM.....Starting running rough and throwing codes today. 1) H-41, 4) H-51, 9) H-64, and H-72. Yesterday I replaced all seals on my A/C again and could not get my compressor to turn on. I wiggled and plugged and unplugged the low pressure switch and the fans came on and so did the a/c. Today when it was throwing codes it would do it everytime I hit a hard bump. I think I have a faulty wire on the a/c circuit at that plug. Does anyone have any advice on this? Replace that switch and plug? Last time I found 2 of the wires touching and it made the car start. This was the same 2 wires on the low pressure switch then too.
09-08-2010, 10:47 AM
#199
Le Mans Master
Don't know how rare your ECM is, one member had good results having his PCM (same thing different year) rebuilt by blue streak.
Last edited by jaa1992; 09-08-2010 at 10:50 AM.
09-08-2010, 09:28 PM
#200
Burning Brakes
I have a new theory about my problem.... SPARK PLUG WIRES! They were new at the time I installed the Delteq kit but I think they may be arking over since they are not routed as tidy as they should be. I think they are probably good but need seperated. I won't be able to get it done until the weekend.... I'll post my results.
Matt