Help with misfire when cold
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Le Mans Master
Joined: Jan 2000
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From: Poway CA
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Help with misfire when cold
The problem started subtle at first.. The car would idle rough for 20-30 seconds on a cold start. After that, everything appeared fine.
Lately it's worse.. Very rough idle for 1-2 minutes, and even throwing a few P0300 codes (misfire).
Last night I pulled the plugs and wires to inspect. Plugs looked fine - none of them wet or fouled. I got a stong whiff of gas when pulling 2 of them - I don't remember that before.. I did notice that theNGK TR55IX electrode caps were loose on many of the plugs. Whoever thought of using a screw-on electrode in a high-performance spark plug should be shot
! I used plyers to tighten the caps and re-installed the plugs.
This morning the problem was back. I remember reading about leaky injectors in older C5s. Mine is a 98 with 45K miles. Could the injectors be flooding the cyclenders while parked? If so, how can I be sure? Is replacing injectors a DIY project? Any other ideas of what to look at?
Thanks,
Lately it's worse.. Very rough idle for 1-2 minutes, and even throwing a few P0300 codes (misfire).
Last night I pulled the plugs and wires to inspect. Plugs looked fine - none of them wet or fouled. I got a stong whiff of gas when pulling 2 of them - I don't remember that before.. I did notice that theNGK TR55IX electrode caps were loose on many of the plugs. Whoever thought of using a screw-on electrode in a high-performance spark plug should be shot
! I used plyers to tighten the caps and re-installed the plugs.This morning the problem was back. I remember reading about leaky injectors in older C5s. Mine is a 98 with 45K miles. Could the injectors be flooding the cyclenders while parked? If so, how can I be sure? Is replacing injectors a DIY project? Any other ideas of what to look at?
Thanks,
Heel & Toe
Joined: Jun 2004
Posts: 20
Likes: 0
From: Medway MA
There are a couple of ways to test injectors on the car. One use a tool called a FI drop tester with a fuel pressure gauge and you can manually open each injector for specified amount of time and make sure they each drop the same amount of fuel. You cycle the key each time to build fuel pressure.
The other way is the same except you use a scan tool to cycle each injector. However if you have access to a scan tool you can look at real time misfire monitor which will tell you which cylinders are misfiring and then you can concentrate your efforts on those cylinders!
The other thing to check is rest pressure. After you shut off the engine the fuel system should maintain a certain amount of pressure....No actual spec for the Vette but the rule of thumb is no more than 15PSI for 15 mins...If not something is allowing the fuel to leak down and in your case it could be the injectors leaking into the cylinders which would explain the cold start up misfire....If this is because of carbon build up a motor vac engine service can do wonders....Also a company called Linder Tech in Indiana rebuilds injectors for cheap compared to new injectors--they can also tell if they get many of these injectors. They also flow match them in sets and have a warranty....
Have not heard of this being a problem with the LS1s but who knows....Sure was with the old CSFI system they put on the trucks! Injectors on the LS1 are easy to change....
The other way is the same except you use a scan tool to cycle each injector. However if you have access to a scan tool you can look at real time misfire monitor which will tell you which cylinders are misfiring and then you can concentrate your efforts on those cylinders!
The other thing to check is rest pressure. After you shut off the engine the fuel system should maintain a certain amount of pressure....No actual spec for the Vette but the rule of thumb is no more than 15PSI for 15 mins...If not something is allowing the fuel to leak down and in your case it could be the injectors leaking into the cylinders which would explain the cold start up misfire....If this is because of carbon build up a motor vac engine service can do wonders....Also a company called Linder Tech in Indiana rebuilds injectors for cheap compared to new injectors--they can also tell if they get many of these injectors. They also flow match them in sets and have a warranty....
Have not heard of this being a problem with the LS1s but who knows....Sure was with the old CSFI system they put on the trucks! Injectors on the LS1 are easy to change....
