Sudden C5 (slight) Power Loss, strange exaust sound. Hmm...
03-22-2014, 04:38 AM
#1
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Sudden C5 (slight) Power Loss, strange exaust sound. Hmm...
Well, after reading this site for months, doing research, I finally purchased my 1st Vette, a 2000 Auto with 30k/mi; immaculate. Two months into it, I'm wondering if my issue is unique. I am adding my first post/issue.... there are lots of appreciated/knowledgeable folk on here!
Up until yesterday am, the car ran like new. Yesterday evening, I did just illuminate the low fuel light while pulling into my garage. I noticed the Corsa exhaust sounded a little different (like a tough lawnmower rather than a beast). Backed it out of garage, and went to fill it up (premium, as always). Noticed, along the drive, that I had what felt like about 15% reduced power, and with the (no longer all that mean) exhaust sound, figured I may be running 7 cylinders, or something.
No Check engine light came on.
Knowing that I know nothing about cars, I went to a dealer/mechanic today. They were mostly confident it was crap fuel, after seeing no major codes, and actually testing the fuel. He cleaned the Throttle Body and Mass Air Sensor, and added K44 detergent (sp?). Said to get Shell/quality fuel, and it should run like new w/in 1/4 tank. I was optimistic.
After running through 2/3 tank, it still sounds off, and performs like a 6cyl. It does not sound catastrophic, and it does idle normal, so they say it's definitely not a coil or cylinder that is misfiring, otherwise "I'd really know".
One other thing to mention - At the same time, the automatic shifting seems too conservative. If I'm in, say 2nd, and step on it a little, it used to accelerate well, or even downshift to 1st and really jump. Now, with medium pressure on the accelerator, it'll speed up a little, then drop into 3rd and really bog. I can still wind'er up to 100mph in 18 seconds, but lost to a Nissan Titan, just to make me even angrier.
I'm headed back to mechanic Monday but, in trying to self-diagnose, am reading lots about alternators, as I notice my headlights dim a little, and the alternator whine does have a pulsing sound with something as basic as power windows being used, or even just the hazards flashing. Could it all (dimming headlights AND performance) be potentially associated with a weak alternator? Hoping they can identify the issue w/o too much expense in "trial and error".
Thank you for any ideas you may have. I hope to return the favor someday, as soon as I can get me some learnin'!
Up until yesterday am, the car ran like new. Yesterday evening, I did just illuminate the low fuel light while pulling into my garage. I noticed the Corsa exhaust sounded a little different (like a tough lawnmower rather than a beast). Backed it out of garage, and went to fill it up (premium, as always). Noticed, along the drive, that I had what felt like about 15% reduced power, and with the (no longer all that mean) exhaust sound, figured I may be running 7 cylinders, or something.
No Check engine light came on.
Knowing that I know nothing about cars, I went to a dealer/mechanic today. They were mostly confident it was crap fuel, after seeing no major codes, and actually testing the fuel. He cleaned the Throttle Body and Mass Air Sensor, and added K44 detergent (sp?). Said to get Shell/quality fuel, and it should run like new w/in 1/4 tank. I was optimistic.
After running through 2/3 tank, it still sounds off, and performs like a 6cyl. It does not sound catastrophic, and it does idle normal, so they say it's definitely not a coil or cylinder that is misfiring, otherwise "I'd really know".
One other thing to mention - At the same time, the automatic shifting seems too conservative. If I'm in, say 2nd, and step on it a little, it used to accelerate well, or even downshift to 1st and really jump. Now, with medium pressure on the accelerator, it'll speed up a little, then drop into 3rd and really bog. I can still wind'er up to 100mph in 18 seconds, but lost to a Nissan Titan, just to make me even angrier.
I'm headed back to mechanic Monday but, in trying to self-diagnose, am reading lots about alternators, as I notice my headlights dim a little, and the alternator whine does have a pulsing sound with something as basic as power windows being used, or even just the hazards flashing. Could it all (dimming headlights AND performance) be potentially associated with a weak alternator? Hoping they can identify the issue w/o too much expense in "trial and error".
Thank you for any ideas you may have. I hope to return the favor someday, as soon as I can get me some learnin'!
03-22-2014, 07:28 AM
#2
Melting Slicks
I don't think the alternator is your issue. The biggest clue (to me) is the car's performance changed when the gas tank ran low. It could be you had some crud in the tank and finally sucked it up and now your fuel filter is plugged. Spend $40 to get a WIX brand fuel filter and replace the one in the car. (Your car probably has the original one and it is now 14 years old.) Don't buy the AC Delco brand filter from the dealership as they will charge $90+ for the same thing. Also, spend the $10 for a fuel filter tool or better yet try to borrow one from Auto Zone.
It will take you longer to jack up the car than it will to replace the filter. Just make sure you have plenty of rags available and don't forget to use the fuel filter tool.
Edit: As for the alternator, the lights dimming etc is pretty normal for these cars. You've noticed it because you're looking for something wrong. If you want peace-of-mind, take your car to Auto Zone and they can test the alternator and battery for you.
I think the dealership was on the right path by thinking you have a fuel related issue but missed the mark because your problem started when your tank ran low; not after a fill up.
Let us know what you find out.
It will take you longer to jack up the car than it will to replace the filter. Just make sure you have plenty of rags available and don't forget to use the fuel filter tool.
Edit: As for the alternator, the lights dimming etc is pretty normal for these cars. You've noticed it because you're looking for something wrong. If you want peace-of-mind, take your car to Auto Zone and they can test the alternator and battery for you.
I think the dealership was on the right path by thinking you have a fuel related issue but missed the mark because your problem started when your tank ran low; not after a fill up.
Let us know what you find out.
Last edited by 3sACROWD; 03-22-2014 at 07:43 AM.
03-22-2014, 07:46 PM
#3
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3sACROWD - Thank you. I'll see what they say about that possibility (fuel filter) and will keep you posted as to whether that was the source, or something else. Thanks again!
03-22-2014, 10:31 PM
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St. Jude Donor '14
If the fuel filter was restricted enough to cause it to lose power and run rough, it should set a lean code/s and turn on the CEL. Does the CEL work? It should be on with key on, engine off.
Most problems that will cause your engine to run rough or lose power will set a code. What does "no major codes" mean? Did they list what the pulled on your r.o.?
You should retrieve the codes and post. Sounds to me the dealer didn't give it much effort. A lot of cars get fixed just using advice from this forum. Bill Curlee, 8vette7 and Dadaroo are very knowledgeable and always give good advice.
Most problems that will cause your engine to run rough or lose power will set a code. What does "no major codes" mean? Did they list what the pulled on your r.o.?
You should retrieve the codes and post. Sounds to me the dealer didn't give it much effort. A lot of cars get fixed just using advice from this forum. Bill Curlee, 8vette7 and Dadaroo are very knowledgeable and always give good advice.
Last edited by martysauto; 03-22-2014 at 11:14 PM. Reason: Typo
03-23-2014, 02:58 PM
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Thank you, MartysAuto. Tricky stuff here. Is there no secondary CEL light that illuminates because the primary CEL light is broken? Ha!
Dropped the car off at the Chevy Dealership, here in Denver. I'll check to see if the CEL works when I can get back to the vehicle. They hope to look at it on Monday or Tuesday, and I'll also list some of the codes. The codes I learner to pull on the cars gauges (using the "options" "gauges" trick someone else posted on this forum), when Googled, were mostly related to the door electronics or items related to having the battery disconnected when I recently had an after-market audio system installed (LDCM, RDCM B2283, B2285, RFA-U1096H, U1064H, U1255 H, etc.). There were probably 20 in all, and I only googled maybe 10 of 'em. Have to assume running a Diagnostic is the 1st thing a certified mechanic would pull, or am I assuming too much? We'll see.... Thanks again!
Dropped the car off at the Chevy Dealership, here in Denver. I'll check to see if the CEL works when I can get back to the vehicle. They hope to look at it on Monday or Tuesday, and I'll also list some of the codes. The codes I learner to pull on the cars gauges (using the "options" "gauges" trick someone else posted on this forum), when Googled, were mostly related to the door electronics or items related to having the battery disconnected when I recently had an after-market audio system installed (LDCM, RDCM B2283, B2285, RFA-U1096H, U1064H, U1255 H, etc.). There were probably 20 in all, and I only googled maybe 10 of 'em. Have to assume running a Diagnostic is the 1st thing a certified mechanic would pull, or am I assuming too much? We'll see.... Thanks again!
03-23-2014, 05:53 PM
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St. Jude Donor '14
I would think they should scan it. Record all codes and check engine data including live and history misfire data. Also long and short term fuel trims at idle, cruise and part throttle acceleration.
03-25-2014, 09:21 PM
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Just closing the loop, for those who chimed in. Dealer claims techs drove car, and with some device, captured a picture/data "snap-shot" of engine performance while they drove, and they are finding nothing wrong. If car still runs poorly, I'll take'er to a specialty shop, for Vette's I guess.
I'll ask them what codes they are getting when I pick it up. Ugh. Hard to be excited about a car that sounds and performs, for no real reason, 15% poorer than it did a day earlier. If I get any updates, I'll update the post. Thank you.
I'll ask them what codes they are getting when I pick it up. Ugh. Hard to be excited about a car that sounds and performs, for no real reason, 15% poorer than it did a day earlier. If I get any updates, I'll update the post. Thank you.
03-25-2014, 10:11 PM
#8
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St. Jude Donor '13-'14-'15
A regular scanner usually only shows old or "history codes" You can have codes stuck into your ECM without ever having the check engine light come on---Only some with tuning software or maybe even a Tech II can pull up "pending codes " Some codes wether false or real--or pending or history WILL put your car into a LIMP mode or reduced power mode----There are several levels of LIMP mode as well---The worst being only allowing you to drive about 45 MPH and the least being losing about 30% of your Torque----
Low voltage will put it into a level of LIMP mode--So will reduced fuel pressure OR fuel volume --Change the filter---To get a LEAN code the Fuel must be lean about 20%--til a code pops up---So if your's is around 19% that's huge at WOT--Because even though the fuel trims are used to correct P/T operation IF you have a LEAN situation it will also add that same % to your WOT fuel as well for a safety-----
Not a big deal at P/T to add 19%--However at WOT if you have a stock tune --the WOT fuel is usually around 11.5:1---So adding 19% at WOT would make your WOT fuel
9.3 !!!!!!!!!!! HORRIBLY RICH and lazy---
Low voltage will put it into a level of LIMP mode--So will reduced fuel pressure OR fuel volume --Change the filter---To get a LEAN code the Fuel must be lean about 20%--til a code pops up---So if your's is around 19% that's huge at WOT--Because even though the fuel trims are used to correct P/T operation IF you have a LEAN situation it will also add that same % to your WOT fuel as well for a safety-----
Not a big deal at P/T to add 19%--However at WOT if you have a stock tune --the WOT fuel is usually around 11.5:1---So adding 19% at WOT would make your WOT fuel
9.3 !!!!!!!!!!! HORRIBLY RICH and lazy---
03-26-2014, 08:30 AM
#9
Racer
pull the codes....write them down.....reset the codes as you go through them....
turn car on for a minute let it run i'd take it for a quick 5 minute spin send it through the gears and then park turn off the car and go back to the codes and see what codes are popping up which would give you a better idea if a code is fresh and coming back or not...
after that if no code seems to be the issue i'd replace the fuel filter and go from there its a cheap and easy fix that you should probably do at this point anyways
if the problem is still persistent then if you would like to check battery then alternator if battery isn't the issue and kinda just go down the checklist of stupid things that could be causing the issue...
i do know though that from past experience not with the vette but another car that a plugged up fuel filter kills performance and does not always through a code...
03-26-2014, 01:02 PM
#10
Drifting
Not Corvette related, but I had a similar incident in my GM pickup while towing a 32' enclosed car trailer. Coming home from a race the wind was blowing very hard and I was having trouble maintaining speed on the highway, thought it was the wind. A hill near my home told me it was not wind related. Truck did not sound strange, just powerless, a new inline fuel filter solved the problem.
03-26-2014, 02:17 PM
#11
Drifting
03-26-2014, 02:58 PM
#12
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St. Jude Donor '08
Clogged /defective CATs. Use an infrared laser thermometer and see if the cat is hotter than the inlet pipe.
Hit the CAT body with a rubber mallet and see if you hear any rattling.
Other than doing a exhaust system back pressure test, its tough to see what is actually going on in the CAT honeycomb matrix. It could be partially clogged enough to not throw any codes but limit performance.
If you have a fiber optic viewer device, you can remove the 02 Sensor and take a look at the matrix face.
Measure fuel pressure and see if it is normal at IDLE and under LOAD. A weak pump or partially clogged filter will look fine at idle and rapidly drop pressure when you put the engine under load.
There is also a fuel volume test that should be accomplished.
If you have a fuel pressure issue, make sure that you have FULL Battery voltage on the fuse (two test points on top of the fuse to ground) and at the fuel pump Positive terminal on the tank.
Bill
Hit the CAT body with a rubber mallet and see if you hear any rattling.
Other than doing a exhaust system back pressure test, its tough to see what is actually going on in the CAT honeycomb matrix. It could be partially clogged enough to not throw any codes but limit performance.
If you have a fiber optic viewer device, you can remove the 02 Sensor and take a look at the matrix face.
Measure fuel pressure and see if it is normal at IDLE and under LOAD. A weak pump or partially clogged filter will look fine at idle and rapidly drop pressure when you put the engine under load.
There is also a fuel volume test that should be accomplished.
If you have a fuel pressure issue, make sure that you have FULL Battery voltage on the fuse (two test points on top of the fuse to ground) and at the fuel pump Positive terminal on the tank.
Bill
03-26-2014, 05:33 PM
#13
Race Director
There's also a history of this behavior due to battery issues. Older cars can also have battery corrosion damage the computer underneath the battery. I too think it's fuel system related, but just sayin'...
03-26-2014, 05:46 PM
#14
Team Owner
Clogged /defective CATs. Use an infrared laser thermometer and see if the cat is hotter than the inlet pipe.
Hit the CAT body with a rubber mallet and see if you hear any rattling.
Other than doing a exhaust system back pressure test, its tough to see what is actually going on in the CAT honeycomb matrix. It could be partially clogged enough to not throw any codes but limit performance.
If you have a fiber optic viewer device, you can remove the 02 Sensor and take a look at the matrix face.
Measure fuel pressure and see if it is normal at IDLE and under LOAD. A weak pump or partially clogged filter will look fine at idle and rapidly drop pressure when you put the engine under load.
There is also a fuel volume test that should be accomplished.
If you have a fuel pressure issue, make sure that you have FULL Battery voltage on the fuse (two test points on top of the fuse to ground) and at the fuel pump Positive terminal on the tank.
Bill
Hit the CAT body with a rubber mallet and see if you hear any rattling.
Other than doing a exhaust system back pressure test, its tough to see what is actually going on in the CAT honeycomb matrix. It could be partially clogged enough to not throw any codes but limit performance.
If you have a fiber optic viewer device, you can remove the 02 Sensor and take a look at the matrix face.
Measure fuel pressure and see if it is normal at IDLE and under LOAD. A weak pump or partially clogged filter will look fine at idle and rapidly drop pressure when you put the engine under load.
There is also a fuel volume test that should be accomplished.
If you have a fuel pressure issue, make sure that you have FULL Battery voltage on the fuse (two test points on top of the fuse to ground) and at the fuel pump Positive terminal on the tank.
Bill
I was thinking that a cat might be clogged.
03-27-2014, 08:27 AM
#15
Melting Slicks
I agree that plugged cats could give the same / similar symptoms but the OP indicates his fuel light came on and now the car is performing different. Based on what was said, it sounds to me that the OP hasn't run the tanks that low before and maybe the previous owner didn't either so there may have been an accumulation of junk (water and debris) in the tank. Running new fuel and additive didn't address the issue so that tends to rule out water. I still hold the low fuel condition as a clue and is why I suggested changing the fuel filter. Changing the filter is inexpensive, easy to do, and should be done on a periodic basis anyway so it isn't a waste of time or money.
The OP indicates the car has Corsa exhaust. Not sure if the car even has cats. The OP would have to let us know if the only thing changed was the axle back or how much of the exhaust system is aftermarket. If the car has factory cats, they have only seen 30k miles of service. Not saying it couldn't happen but I think 30k miles is premature on cat failure.
The OP indicates the car has Corsa exhaust. Not sure if the car even has cats. The OP would have to let us know if the only thing changed was the axle back or how much of the exhaust system is aftermarket. If the car has factory cats, they have only seen 30k miles of service. Not saying it couldn't happen but I think 30k miles is premature on cat failure.
03-27-2014, 03:19 PM
#16
Burning Brakes
Well, after reading this site for months, doing research, I finally purchased my 1st Vette, a 2000 Auto with 30k/mi; immaculate. Two months into it, I'm wondering if my issue is unique. I am adding my first post/issue.... there are lots of appreciated/knowledgeable folk on here!
Up until yesterday am, the car ran like new. Yesterday evening, I did just illuminate the low fuel light while pulling into my garage. I noticed the Corsa exhaust sounded a little different (like a tough lawnmower rather than a beast). Backed it out of garage, and went to fill it up (premium, as always). Noticed, along the drive, that I had what felt like about 15% reduced power, and with the (no longer all that mean) exhaust sound, figured I may be running 7 cylinders, or something.
No Check engine light came on.
Knowing that I know nothing about cars, I went to a dealer/mechanic today. They were mostly confident it was crap fuel, after seeing no major codes, and actually testing the fuel. He cleaned the Throttle Body and Mass Air Sensor, and added K44 detergent (sp?). Said to get Shell/quality fuel, and it should run like new w/in 1/4 tank. I was optimistic.
After running through 2/3 tank, it still sounds off, and performs like a 6cyl. It does not sound catastrophic, and it does idle normal, so they say it's definitely not a coil or cylinder that is misfiring, otherwise "I'd really know".
One other thing to mention - At the same time, the automatic shifting seems too conservative. If I'm in, say 2nd, and step on it a little, it used to accelerate well, or even downshift to 1st and really jump. Now, with medium pressure on the accelerator, it'll speed up a little, then drop into 3rd and really bog. I can still wind'er up to 100mph in 18 seconds, but lost to a Nissan Titan, just to make me even angrier.
I'm headed back to mechanic Monday but, in trying to self-diagnose, am reading lots about alternators, as I notice my headlights dim a little, and the alternator whine does have a pulsing sound with something as basic as power windows being used, or even just the hazards flashing. Could it all (dimming headlights AND performance) be potentially associated with a weak alternator? Hoping they can identify the issue w/o too much expense in "trial and error".
Thank you for any ideas you may have. I hope to return the favor someday, as soon as I can get me some learnin'!
Up until yesterday am, the car ran like new. Yesterday evening, I did just illuminate the low fuel light while pulling into my garage. I noticed the Corsa exhaust sounded a little different (like a tough lawnmower rather than a beast). Backed it out of garage, and went to fill it up (premium, as always). Noticed, along the drive, that I had what felt like about 15% reduced power, and with the (no longer all that mean) exhaust sound, figured I may be running 7 cylinders, or something.
No Check engine light came on.
Knowing that I know nothing about cars, I went to a dealer/mechanic today. They were mostly confident it was crap fuel, after seeing no major codes, and actually testing the fuel. He cleaned the Throttle Body and Mass Air Sensor, and added K44 detergent (sp?). Said to get Shell/quality fuel, and it should run like new w/in 1/4 tank. I was optimistic.
After running through 2/3 tank, it still sounds off, and performs like a 6cyl. It does not sound catastrophic, and it does idle normal, so they say it's definitely not a coil or cylinder that is misfiring, otherwise "I'd really know".
One other thing to mention - At the same time, the automatic shifting seems too conservative. If I'm in, say 2nd, and step on it a little, it used to accelerate well, or even downshift to 1st and really jump. Now, with medium pressure on the accelerator, it'll speed up a little, then drop into 3rd and really bog. I can still wind'er up to 100mph in 18 seconds, but lost to a Nissan Titan, just to make me even angrier.
I'm headed back to mechanic Monday but, in trying to self-diagnose, am reading lots about alternators, as I notice my headlights dim a little, and the alternator whine does have a pulsing sound with something as basic as power windows being used, or even just the hazards flashing. Could it all (dimming headlights AND performance) be potentially associated with a weak alternator? Hoping they can identify the issue w/o too much expense in "trial and error".
Thank you for any ideas you may have. I hope to return the favor someday, as soon as I can get me some learnin'!
03-27-2014, 03:29 PM
#17
VERY BAD ADVICE, especially on modern computer controlled charging systems like the C5. A VOLTMETER is the BEST way to check the charging system (short of an oscilloscope).
03-27-2014, 09:57 PM
#18
I agree with 3boy, Check voltage at the batteries at idle and above 1200 rpm, turn on all loads you can. Headlights, a/c or heater, turn signal, radio, wipers. Then check battery voltage. You should not go below 13.2.
03-29-2014, 09:05 PM
#19
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St. Jude Donor '13-'14-'15
Dis connecting the battery while running can send a voltage spike to your ECM and kill it--Now you have to walk home !!!--Old school method for carbs and non computer engines
03-29-2014, 09:30 PM
#20
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St. Jude Donor '08
I AGREE!! NEVER EVER disconnect the battery with the engine running on a computer controlled vehicle The alternator is internally regulated and uses battery Buss Voltage (the battery) as reference voltage. If the alternator sees ZERO volts reff, it will go full output. The modules in the car (PCM, BCM IPC, RFA, EBTCM, HVAC SCM etc... ) will NOT be happy!!!!
Bill
