Hard Cold Cold Start
Thread Starter
Safety Car
Joined: Dec 1999
Posts: 4,691
Likes: 1
From: Framingham MA
Hard Cold Cold Start
This has been a very frustrating issue for my car. It has had a hard cold start for 3 years now. I have done some diagnostic work on this problem and I thought I had it fixed, when I found the top of the coolant sensor to be loose.
Basically the injector pulse is very weak when I place a test light on it. When it starts the test light is bright. Once slightly warmed up it runs and starts fine (1 minute).
-I have good fuel pressure (no leaking injectors, fuel pump, system holds 40psi of pressure over night)
-New coolant sensor, New ECM, I swapped distributors, new pickup coil, ignition coil.
-Once started it doesn't smell rich (ie missing firing)
-Cold start cicuitry is fine, it starts the same with and without it connected. Cold start isn't supose to work until below 40 anyways.
No codes, I just don't what to look for next. I assume the issue is the injectors not intially firing but I don't know what causes that.
Basically the injector pulse is very weak when I place a test light on it. When it starts the test light is bright. Once slightly warmed up it runs and starts fine (1 minute).
-I have good fuel pressure (no leaking injectors, fuel pump, system holds 40psi of pressure over night)
-New coolant sensor, New ECM, I swapped distributors, new pickup coil, ignition coil.
-Once started it doesn't smell rich (ie missing firing)
-Cold start cicuitry is fine, it starts the same with and without it connected. Cold start isn't supose to work until below 40 anyways.
No codes, I just don't what to look for next. I assume the issue is the injectors not intially firing but I don't know what causes that.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
What year Vette??
Which coolant temp sensor did you replace?
Have you checked for vacuum leaks?
Are all the spark plugs in good condition?
If you clip a timing light in turn onto each spark plug wire does the engine miss coincide with missed flashes on any wire(s)?
Which coolant temp sensor did you replace?
Have you checked for vacuum leaks?
Are all the spark plugs in good condition?
If you clip a timing light in turn onto each spark plug wire does the engine miss coincide with missed flashes on any wire(s)?
Thread Starter
Safety Car
Joined: Dec 1999
Posts: 4,691
Likes: 1
From: Framingham MA
Originally Posted by 65Z01
What year Vette??
Which coolant temp sensor did you replace?
Have you checked for vacuum leaks?
Are all the spark plugs in good condition?
If you clip a timing light in turn onto each spark plug wire does the engine miss coincide with missed flashes on any wire(s)?
Which coolant temp sensor did you replace?
Have you checked for vacuum leaks?
Are all the spark plugs in good condition?
If you clip a timing light in turn onto each spark plug wire does the engine miss coincide with missed flashes on any wire(s)?
Vacuum lines all replaced 600 miles ago, same with the spark plugs and cap/rotor.
I haven't tried looking at with a timing light, I will try that next.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Looks like you may have found it since the test light is weak when it isn't running. How's the battery? Check for high resistance in the injector circuit - fuses to injectors - ground or driver side back to the ECM. Check cold start circuitry too - as far as I know, it operates anytime coolant temp is below 100 degrees.
