C5Z rough idle after start
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C5Z rough idle after start
2001 C5Z idles rough after start for about 10-30secs then evens out. During those 10-30sec if I press the gas pedal it want to die. Cleaned TB, MAFs, checked for vac leaks. Maybe leaky injectors, O2 Sensors ? Any help would be awesome.
Drifting
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From: North pole
have you checked fuel pressure on start up? Plugs,wires,fuel filter..any of those changed
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Drifting
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From: North pole
does this happen after its warmed up..cold startup?
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From: Anthony TX
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At cold start (OPEN LOOP),, The O2 sensors are NOT used to calculate AFR during cold start. Its a pre programmed TABLE that enriches the mixture. Once it goes into CLOSED LOOP, the PCM uses the O2s.
You are either TOO RICH or TOO LEAN and need to figure that out. If the car drives fine after warm up and under heavy LOAD,, I wouldn't be concerned about the filter. The engine used WAYYYY ore fuel under load and cruising than at cold start. That being said, I would still check fuel pressure at Key On (engine cold).
You can pop the fuel rail OFF the manifold and turn on the key and see if any of the injectors are leaking.
Please list the status of plugs and wires (AGE & CONDITION)
Clean the MAF and throttle blade and make SURE that there are not any un-metered air leaks between the MAF and TB!
Bill
You are either TOO RICH or TOO LEAN and need to figure that out. If the car drives fine after warm up and under heavy LOAD,, I wouldn't be concerned about the filter. The engine used WAYYYY ore fuel under load and cruising than at cold start. That being said, I would still check fuel pressure at Key On (engine cold).
You can pop the fuel rail OFF the manifold and turn on the key and see if any of the injectors are leaking.
Please list the status of plugs and wires (AGE & CONDITION)
Clean the MAF and throttle blade and make SURE that there are not any un-metered air leaks between the MAF and TB!
Bill
Last edited by Bill Curlee; May 4, 2018 at 12:19 AM.
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It does it every time I start the car- longer when it's a cold start.
See below- message is in your post. Thanks
If it does it only on the 1st time starting I'm sensing plug wires.
I have a new filter on its way so Ill have to wait n see. I'll keep you posted on the progress but my initial thought was leaky injectors because I could smell a strong fuel smell in the engine bay. See like it's running too rich.
If it does it every single time I'm leaning Fuel Filter/Fuel Pressure Regulator.
I have a new filter on its way so Ill have to wait n see. I'll keep you posted on the progress but my initial thought was leaky injectors because I could smell a strong fuel smell in the engine bay. See like it's running too rich.
If it does it every single time I'm leaning Fuel Filter/Fuel Pressure Regulator.
Last edited by Jrodriguez; May 4, 2018 at 01:36 AM.
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Smells rich
Will Do, thanks!!! It does smell rich when I start it. Gas smell in the engine bay on the drivers side is strong. I just changed the plugs and wires look good MSD.
QUOTE=Bill Curlee;1597129897]At cold start (OPEN LOOP),, The O2 sensors are NOT used to calculate AFR during cold start. Its a pre programmed TABLE that enriches the mixture. Once it goes into CLOSED LOOP, the PCM uses the O2s.
You are either TOO RICH or TOO LEAN and need to figure that out. If the car drives fine after warm up and under heavy LOAD,, I wouldn't be concerned about the filter. The engine used WAYYYY ore fuel under load and cruising than at cold start. That being said, I would still check fuel pressure at Key On (engine cold).
You can pop the fuel rail OFF the manifold and turn on the key and see if any of the injectors are leaking.
Please list the status of plugs and wires (AGE & CONDITION)
Clean the MAF and throttle blade and make SURE that there are not any un-metered air leaks between the MAF and TB!
Bill[/QUOTE]
QUOTE=Bill Curlee;1597129897]At cold start (OPEN LOOP),, The O2 sensors are NOT used to calculate AFR during cold start. Its a pre programmed TABLE that enriches the mixture. Once it goes into CLOSED LOOP, the PCM uses the O2s.
You are either TOO RICH or TOO LEAN and need to figure that out. If the car drives fine after warm up and under heavy LOAD,, I wouldn't be concerned about the filter. The engine used WAYYYY ore fuel under load and cruising than at cold start. That being said, I would still check fuel pressure at Key On (engine cold).
You can pop the fuel rail OFF the manifold and turn on the key and see if any of the injectors are leaking.
Please list the status of plugs and wires (AGE & CONDITION)
Clean the MAF and throttle blade and make SURE that there are not any un-metered air leaks between the MAF and TB!
Bill[/QUOTE]
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From: Anthony TX
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Check the actual SPARK quality on each bank to make sure that you have good spark.
Each bank has its own coil power fuse and one side could have poor voltage feed to that bank and cause a cold miss.
Each bank has its own coil power fuse and one side could have poor voltage feed to that bank and cause a cold miss.
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From: North pole
Also check the wiring harness on the drivers side that go to the injectors,coils..there is a bracket at the corner of the mainfold sometimes the bracket cuts into the harness and causes all kinds of problems!
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From: Cape Coral, Florida
Hi !!
Sorry to hear your car is running rough...do you own a decent scan tool too see if maybe you have any misfire codes or other codes...CEL on ???...without it and a decent knowledge of engine diagnostics especially fuel trims and O2 system operation...after 10-30 seconds you are still in "open loop" so your fuel trims would not be controlled by the PCM...you'll just be shot gunning parts !!...could be vacuum leak, fuel delivery, injector problems etc...etc...and remember you can change parts but if there are wiring issues with these parts you are back to square one !!
p.s. You said you are smelling a strong gas odor on the drivers side...maybe a fuel injector mechanically stuck open for a little bit...you can pressurize the fuel rail KOEO...the fuel pump has a 2 second prime then see if your fuel pressure leaks down quickly...it should hold !!...you can buy a decent scan tool these days for $100.00...CMON MAN !!...spend that cash !!...you own a Vette for Gods sake...LOL !!...there was someone on this site who I sent my old Actron scan tool to and hopefully he can get his rough idle fixed...he should be receiving it today....I currently have 2 now...my Autel which is bi-directional and my factory TIS Techstream for my Toyota 4 Runner daily driver. Good luck and hope you get it fixed...keep us updated !!
Sorry to hear your car is running rough...do you own a decent scan tool too see if maybe you have any misfire codes or other codes...CEL on ???...without it and a decent knowledge of engine diagnostics especially fuel trims and O2 system operation...after 10-30 seconds you are still in "open loop" so your fuel trims would not be controlled by the PCM...you'll just be shot gunning parts !!...could be vacuum leak, fuel delivery, injector problems etc...etc...and remember you can change parts but if there are wiring issues with these parts you are back to square one !!
p.s. You said you are smelling a strong gas odor on the drivers side...maybe a fuel injector mechanically stuck open for a little bit...you can pressurize the fuel rail KOEO...the fuel pump has a 2 second prime then see if your fuel pressure leaks down quickly...it should hold !!...you can buy a decent scan tool these days for $100.00...CMON MAN !!...spend that cash !!...you own a Vette for Gods sake...LOL !!...there was someone on this site who I sent my old Actron scan tool to and hopefully he can get his rough idle fixed...he should be receiving it today....I currently have 2 now...my Autel which is bi-directional and my factory TIS Techstream for my Toyota 4 Runner daily driver. Good luck and hope you get it fixed...keep us updated !!
Last edited by C5 Diag; May 11, 2018 at 09:46 PM.
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Missing both down stream 02 Sensors
I believe my C5Z comes Stock with 4 02 sensors. Looks to me like the previous owner capped the 2 that are in the middle of the exhaust. I still have the 2 closest to the headers. I also noticed that the wiring is still there for both sensors not being used but they have some type of black block plugged in to them. This car has headers, not cats, 2 O2 sensors, and the original Tit.. mufflers. Can this be the reasons for a rough idle at start and gassy smells from the exhaust. Checked injectors and they are not leaking. I did get a check valve code.
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From: Cape Coral, Florida
I believe my C5Z comes Stock with 4 02 sensors. Looks to me like the previous owner capped the 2 that are in the middle of the exhaust. I still have the 2 closest to the headers. I also noticed that the wiring is still there for both sensors not being used but they have some type of black block plugged in to them. This car has headers, not cats, 2 O2 sensors, and the original Tit.. mufflers. Can this be the reasons for a rough idle at start and gassy smells from the exhaust. Checked injectors and they are not leaking. I did get a check valve code.
With headers, missing Cat, and your 2 missing downstream sensors I don’t see how your PCM can accurately schedule fuel...yes, this can definitely be the cause of your issues and in some states it is illegal to operate your car without a cat...probably best to take your car to a “tuner” and see what they could do...there are just too many variables here...good luck !!
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From: Cape Coral, Florida
How about we do this...let's see if that injector is leaking...do you have a fuel pressure gauge ??...the car has a Schrader valve on the fuel rail so it's pretty easy to check...Turn the key on and wait for the fuel pressure to rise...turn the key off...pressure should hold...now we need to determine if the PCM driver is shorted or the injector is bad...unplug the harness from the injector...if the pressure holds you have a wiring problem...if it doesn't you have a bad injector !!