1988 GMC

[longhorn314]

I bought a 1988 GMC 4x4 3/4 ton last year for a farm truck.I had a complete tune-up done on it when I bought it.Recently ,when you go and start it, it wants to die with you and you have to keep your foot on the accelerator for about 3 or 4 minutes, then it is fine.It has a new battery and a new alternator that has been on for about 6 months.But then after it is cranked and running it is fine all day until the next day and it will do the same thing.Anyone have any other ideas as to what it may be?

 

[Saltydawg]

When you first go out in the morning and crank it........

Does it not fire until you've cranked it a while?

Does it fire and then die unless you keep your foot on the gas reving the engine?

Is it fuel injected or carburated and what engine is in it?

 

[ALACOWMAN]

Its a throttle body injected. could be a few things firsts two things comes to mind is either a coolant sensor or idle air control valve . have you checked all vacuum hoses. i just talked to the mech. he seems to think its the coolant sensor.this is the sensor for the computor system that tells the computor the eng temp so the computor adjusts the fuel according to temp

 

[longhorn314]

it is a fuel injected 350 4 speed.I forgot to mention the service engine light started coming on about the same time and I have a little old cheap tester and when I test it , the code I think it says in the book says something about a coolant sensor but I wasn't for sure if that would be the problem.May be worth a check

 

[Saltydawg]

Like Alacowman said...it is likely the coolant sensor.

The computer uses this temperature reading to adjust the fuel mixture for cold starting.
Cold engines require a richer fuel mixture to run well.

Same principle as a choke just done in a different manner.

 

[baldy]

since this is a throttle body setup....can you just convert these to a regular carburater set up...just wondering