ScaryFast

OK, here's the latest. Got the optispark working properly and I'm back where I was Friday (before 35 hours of Opti replacement and tweaking).

The car runs for a sec then stalls and will not restart.

Soooo what have I learned? A lot of things that are not the problem.

In this process I have replaced the opti, fuel filter, battery, and plugs. I've checked each plug wire and all have similar resistance (~4KOhms) and I've checked and double checked the wire routing. I have spark at the plugs (although it is sometimes orange instead of blue, any significance to that?)

It's down to one of two things:

Injectors
ECM

I had two faults when I plugged in a scan tool last week: DTC 66 A/C something (HVAC is gone so not surprising) and DTC 38, QDM 3 - quad driver module 3.

I have 47 psi at the fuel rail during crank, it doesn't fluctuate much at crank nor once the car briefly runs. To me this eliminates fuel supply (pump and filter).

Therefore, perhaps the injectors are shot or the ECM is not commanding them to open and spray.

I was able to discuss with a buddy that was a Chevy mechanic for several years through the 90's. He is convinced that the QDM failure means bad ECM. They're cheap ($160) so I'm going to try it. I have to order it so it will be Thursday before I get it in the car, any more suggestions until then?

jfb

You got good advice from your mechanic. If you had tested each injector with a Noid light (or a low power 12v lamp in place of each injector) you would have found that some of the injectors were not being pulsed by the ECM. A new ECM will fix that.

bobmic93

Just a cheap shot in the dark here. I had a mechanic telling me I needed a new ECM because of a certain code thrown. Turn out to be a fuse that some how protectes the Ecm. Its worth just a look.

ScaryFast

I'll check both. Any idea which fuse? I've checked most and they're ok. Oh, one more thing. Several friends have come by at various occasions and brought different brands of brown pops during my ordeal. The most important thing I've learned so far is that I'm ok with any of the following when working on cars:

Bud
Bud Light
Bud Select
Miller
Miller Lite
Corona

I do not enjoy heavier beers while in the garage in 90+ temps and high humidity such as:

Oberon
Guiness
Anything else that isn't relatively similar in color to the fuel that spilled all over my garage floor due to improper catch pan location.

Morley

If all of the ECM related fuses are good and you are throwing a code for a quad driver...its more than likely the ECM is shot.
I used to have a throuble shooting chart for testing the quad drivers, wish I could remember where I put it.
Anyone on here have one? Know what I'm talking about? Got it from an ECM remanufacturer.

Swampy

There are many things it could be and most are pricey. A lot of the guys on here are right up on certain aspects of it and sure give some great places to start your search for the cause. I take the time now to cut and paste all there input to a saved file on vettes and it is indeed a wealth of information. Even when its the same info, someone may present it better than another and it sends out a clue to you.

Here the dealers seem to start at the most expensive and tell you what its not, rather than what it is. The better street rod shops do a better job most of the time. There is one local vette shop here, but you better bring $$$$$$$$$$$$ and your first born.

I've found this site to be the most helpful in keeping them running right.
The little tips these guys pass on are well worth saving. If they don't apply now, there is a good chance the will later for sure.

I'm and older guy, age 63 so I learned it all on old carb cars, trucks and boats. They sure have complicated it and made a need for test gear.
So much stuff dependant on what the computer says or eprom or or or.... I liked the days of a screw driver, a good ear and a timing light.
I sure do enjoy the handling of the vettes of today. Engine wise I'd be just as happy with a carbed unit I could understand without being a grad of MIT....

I've been following your thread, very good one and it seems like once you connect the right dots your all set....For sure your learning about of new stuff to keep in mind. I find this more helpful than the manuals at time....they just say it clearer or keep it in the KISS mode to where its just simplier.

My son and I both have a couple of vettes and just enjoy working with them. We buy and sell them from time to time, upgrade and in general do it just for a hobby. I really do it now more to just spend time with my sons. One way of hanging on to my youth.

My son is becoming very good on the electronics of them in the newer models and has been offered a job for one of the local vetter restoration and repair shops. He prefers to do it as a hobby not a job so he passed on it as he has a job in electronics now anyhow.

Good luck and continue to keep us posted, really courious now as to what it is.

Swampy

ScaryFast

Another thought - the ECM needs three inputs to run, MAP, TPS, and temp.

I assume the throttle sensor is OK because when it did run (last thursday was the last time) there were no issues. If the MAP is going bad I suppose it could be intermittant. I might as well check the temp sensor as well.

Swampy, thanks for the sentiment...I'll keep everyone posted.

Look for this to show up as a miniseries on TLN this fall.

Redeasysport

Don't think it is MAP mine runs with it disconnected.Nor do i think temp sensor unless it is shorted.Wish I could comment on the quad driver but try disconnecting the battery and reset the codes check all ECM connectors,reseat the memcal(there is a little plate on the bottom of the ECM to acess it) and try again and see if the same codes pop up.I always like to double and triple check stuff like this as different codes can be set.

SJW

It's highly unlikely that you'd have more than one injector fail at the same time, and one failed injector is very unlikely to cause your engine to die after running for two seconds. Unless you're seeing black smoke out the tailpipes, and it's acting like it's flooding with fuel, forget about bad injectors. But don't rule out the possibility that the injectors are not being commanded to open and close.

I've been following along with you on this thread so far, and have asked if you've checked FP. Did I miss a post somewhere that said you checked it? If not, monitor FP with a gauge until you can get the car to misbehave, and see what the FP is doing at that time. What you are seeing is about what I'd expect if the fuel pump is failing to energize when the ignition switch is in the RUN position.

To start with, break the problem in half. Figure out if it's a fuel delivery problem, or a spark-delivery problem. It's gonna be one or the other. Verify or rule out a fuel-delivery problem first. Until you're sure that the fuel rail is pressurized correctly at all times, stop looking elsewhere. If the fuel rail is pressurized correctly at all times, make sure the injectors are seeing pulses.

If it's not a fuel system problem, check the coil wire, but forget about the plugs or plug wires. There's no way the plugs or plug wires will cause an engine to run for two seconds, then quit.

Don't rule out the coil or ignition control module that triggers the coil based upon inputs from the ECM. Don't replace any of them yet, but keep them in mind.

Keep your $ in your pocket until you get the problem diagnosed. I hate to see you throwing lots of parts at the problem, only to end up frustrated because nothing has changed.

froggy47

Can I come work in your garage?

ScaryFast

The latest:

I checked fuel pressure last night and had ~47 psi after turning on the pump and during crank. The car doesn't turn over long enough to check while the motor is running, but there was no noticeable dip (maybe a +/- 2 psi fluctuation) while cranking. I replaced the fuel filter also, that never hurts.

Tonight I checked the injector firing with a noid light. It looks as if the injector is fired twice, then no more signals are sent. The first fire per crank attempt I get several rapid flashes of the light and the second just a few, then nothing until I stop cranking for a minute and start again.

My assumption would be that the ECM should keep firing them, but perhaps I'm wrong. Does it assume that there is enough fuel in the cylinder after a few sprays and stop opening them until the existing fuel combusts? Or should it continue to fire the injectors as long as I crank?

I'm getting spark consistantly at the plug side of the plug wires, so I don't think it's a spark problem.


Tomorrow I'm checking the ECM. I know someone with another '93 so I'm going to drop my computer into his car and see if it starts. VATS should not care, correct? It will be his key and his CCM, my assumption is that if my computer is OK then it will start his car. Any thoughts on that? I don't want to stick his ECM in my car in case whatever problem blew it up in the first place is still there.

ScaryFast

Yes, but please bring one of the sodas listed in the top list

I'll supply the music, the girls, and the frustrated cursing.

Redeasysport

Did you clear and recheck your Fault code? Is it still showing ECM?
Your fuel pressure seems ok it should drop a little when fired up.From what I have read there is no problem swapping a ECM.I have not read of another car wiping one out by swaping them in fact there have been many suggestions to do what you plan.It is the only way to be sure before spending the money.

I also do not recall any external components having taken an ECM out.They just fail and need replaced from time to time.Make sure to swap the memcal out when you swap them.

adelii

I've read your thread to include all the replies. All are very good and you won't get bad ones. But your problem is the ignition module. You say you have a friend with a 93 similar to yours. Take the module from his car and try it on yours. The problem should go away. By the way when you do the test you don't have to remove your module. Just your friends. The test is quick and the car should start. Just DON'T try checking the module with a meter. It will mess it up. After this test, you can go on with any other exchange you want. This is a quick test and cheap. I believe the module is less expensive than the ECM. Good Luck.

Morley

The reason the injectors aren't firing more is that the ECM isn't seeing the refrence pulse from the distributor. There's a couple of things to check. Ignition module (mentioned above), if a different module doesn't fix it then you have an open on the wire from the module to the ECM OR back to the dreaded bad ECM.

ScaryFast

What's the memcal? You mean the PROM underneath? Why do I need to swap that?

Redeasysport

Yes the prom it is specific to each car and is what you must transfer into a new one.Not sure of all the specifics of why mabey someone else can chime in here or try a search.

ScaryFast

It's not the ECM.

I put it into the other '93 (PROM and all) and his car fired up immediately and ran like a champ.

On to the ignition.

Morley, I have connections from the Opti to the ECM, do you mean the line between the ignition module and ECM could be bad?

I couldn't check the ignition module on the other car...didn't have time.

Redeasysport

Cool eliminate one more thing.You ought to try swapping modules if you can. The wires from the opti go up under the pass injector covers then to ecm a short or bad contact anywhere in the loop is bad.There is also a harness for the module.Do a search on the ignition module there is a lot of good posts on how to remove and replace it.It must be done right with heat sink paste.
You said code 38 quad driver there is no code 38 did you mean 28?
here is some light reading
http://forums.corvetteforum.com/show...er&forum_id=48

http://www.aceesolutions.com/vette/c4codes.html

http://forums.corvetteforum.com/show...ad&forum_id=48
From these it seems code 28 is not your problem.


Code Circuit or Sensor
13 Oxygen Sensor Circuit
14 Coolant Sensor Circuit (High)
15 Coolant Sensor Circuit (Low)
16 Ignition Pblms (Used on 1992-1996 models only)
21 Throttle Position Sensor (TPS) (High)
22 Throttle Position Sensor (TPS) (Low)
23 Intake Air Temperature (Low)
24 Vehicle Speed Sensor (VSS)
25 Intake Air Temperature (High)
26 Quad Driver Module Number 1
27 Quad Driver Module Number 2
28 Quad Driver Module Number 3
32 Exhaust Gas Recirculation Circuit
33 Mass Air Flow Sensor Circuit (1985-1990)
33 Manifold Absolute Pressure High (1984)
34 Mass Air Flow Circuit (1985-1990)
34 Manifold Absolute Pressure Low (1984)
35 Idle Air Control Circuit (IAC)
36 Mass Air Flow Burn Off Circuit
41 Cylinder Select Error Circuit (1985-1991)
42 Electronic Spark Timing Circuit (EST)
43 Knock Sensor Circuit
44 Lean Exhaust Present
45 Rich Exhaust Present
46 VATS Anti Theft Circuit Fault
51 PROM/EEPROM Error
52 Oil Temperature Circuit (Low Temperature)
53 System Charging Voltage High or Low
54 Fuel Pump Circuit (Low Voltage)
55 Engine Running Lean
62 Oil Temperature Circuit (High Temperature)
63 Oxygen Sensor Circuit (Open)
64 Oxygen Sensor Circuit (Lean Exhaust)
65 Oxygen Sensor Circuit (Rich Exhaust)
66 Air Conditioner Pressure Limit Exceeded
67 Air Conditioner Pressure Limit Exceeded
68 Air Conditioner Relay Fault
69 Air Conditioner Clutch Fault
72 Gear Selector Switch Fault (Start Lockout)

Possible Failures Associated with ECM Codes (From most likely to least likely)

13 Check wiring and connectors. Bad Sensor
14 Check wiring, connectors, thermostat. Monitor actual engine temperature. If within limits, and wiring/connector is OK, change thermostat and/or sensor.
15 See above, particularly thermostat
16 Direct Ignition (DI) Fault
21 Sticking or Misadjusted TPS. Also check wiring/connectors. Adjust/replace TPS.
22 Sticking or Misadjusted TPS. Also check wiring/connectors. Adjust/replace TPS.
23 Measure sensor resistance with Digital Ohm meter. Must not be 0 ohms or infinite ohms. Replace if it shows one of these readings. Check wiring/connector of sensor. If OK, replace sensor.
24 Only valid if vehicle moving. Check connections at ECM Check TPS setting. Possible ECM failure.
25 Measure sensor resistance with Digital Ohm meter. Must not be 0 ohms or infinite ohms. Replace if it shows one of these readings. Check wiring.connector of sensor OK.
26 Check EGR, Canister Purge and AIR pump relays with a digital Ohm meter. A resistance of less than 18 ohms indicates a bad relay. If OK, potential ECM failure.
27 Potential ECM or on a manual transmission car, potential upshift relay problem. Check relay, replace if less than 18 Ohms using a digital Ohm Meter.
28 Air conditioning Clutch relay and/or cooling fan relays. Check with digital Ohm meter, replace if less than 18 Ohms. If relays OK, potential ECM failure.
32 The most common cause of this code is a bad or intermittent EGR switch which is located on the EGR pipe between the exhaust manifold and the intake manifold. Replace this switch first when you get this code. Next, check electrical connections at EGR valve solenoid and then the ECM. Check all vacuum lines for leaks especially around the EGR valve. Possible ECM failure.
33 (1985-1990) Inspect intake system for leaks, Inspect for vacuum leaks, Check MAF connector and wiring, Check MAF for open using digital Ohm meter. Possible ECM failure.
33 (1984) Check vacuum hoses. Check wiring to sensor. Change sensor. Check connections at ECM.
34 (1985-1990) Clean the throttle body. Check MAF connections. Replace MAF relay. Replace MAF Sensor. Possible ECM failure.
34 (1984) Check Vacuum hoses associated with MAP sensor. Check wiring and connections, particularly at ECM. Replace the sensor. Possible ECM failure.
35 Check fuel pressure, injectors, leaking throttle body. Change the IAC valve.
36 Check connections at MAF, MAF relay and MAF Burn off relay. Check resistance of MAF relay and MAF burnoff relay with digital Ohm meter. replace if less than 18 Ohms. Possible ECM failure.
41 Check wiring at ECM. Possible PROM failure, or incorrectly seated PROM. Reseat PROM. Possible ECM failure.
42 Check wiring at ignition module. Replace ignition module. Possible ECM failure.
43 Check ECM wiring. Replace knock sensor
44 Check wiring.connectors at Oxygen sensor. Check fuel pressure. Replace Oxygen sensor.
45 Check evaporative charcoal canister for smell of fuel (which normally comes from filling fuel tank to full). check fuel pressure regulator. Possible leaking fuel injector or sticking/bad EGR valve. Possible bad Oxygen sensor.
46 With negative battery lead disconnected and using high pressure, non residue contact spray cleaner, spray into area where ignition key inserts followed by inserting and removing key several times. Check for open/short on harness from steering column VATS ignition key to ECM. Possible defective anti-theft module.
51 Faulty or incorrect PROM in the ECM. Change PROM with correct version for automobile.
52 Check connections at the oil temperature switch. If OK, replace switch.
53 If voltage is more than 17.1 or less than 10 volts, this code will be set. Check battery leads, alternator drive belt for tightness and have electrical shop check alternator output. Voltage with engine off should be 12 volts. Voltage with engine running should be 14-15 volts. Use digital volt meter for checks and measure at the battery terminals.
54 Using digital Ohm meter, check fuel pump circuits for shorts or opens.
55 This code is set when there is not enough fuel when accelerating. A possible fuel pump failure or insufficient fuel pressure due to a fuel line restriction is indicated.
62 Check wiring associated with Oil temperature switch. Replace switch.
63 Check wiring and connections to Oxygen sensor.
64 Check wiring and connections from Oxygen sensor to ECM. Check ECM ground terminal and battery ground. Check fuel pressure and fuel pump. Replace Oxygen sensor if all of above OK.
65 Check evaporative charcoal canister for fuel fumes. Replace if contaminated. Check oil for presence of fuel. Check fuel pressure regulator, fuel pump, check for leaking injectors, Check for stuck/defective EGR valve, Replace Oxygen sensor if all above OK.

ScaryFast

Is there a way to diagnose the ignition module? Someone mentioned not to test it with a meter or it will fry.

I checked the connections to the opti before I replaced it, but there's no harm in checking again.