Hello all.Im new to this site,and wanted to see if anyone could help me with a problem.
I have a 92 NITE short bed Flare Side 4x4 5.0 that wont idle on initial start up in the morning.This just started doing it out of the blue. It will initially start,but will die imediatly.I have to keep the throttle open,and drive with 2 feet until it warms up,but idles once warm.The check engine light comes on at idle,or when i let off the gas.In the afternoon,this problem,and the check engine lite disapears until next the morning when i start up to go to work.Then the problem starts all over again.Any help will be greatly apreciated.Thanks,Chris

 

Well, the computer has no real memory in those years of truck, So you need to get the computer scanned while the light is on. The problem sounds like either a sticking IAC or a lean condition. It seems to me that there was somewhat of a problem in those years for upper intake gaskets. Have you done any work on the truck lately?? Best way would to get it scanned.

 

Since you say it runs fine with the throttle partway open i would say its the idle control valve. They tend to act up more when cold so that could explain why it's only in the morning. Try this, before you start it tomorrow morning pull off a big vacuum line that goes right to the intake manifold, such as a pcv line or the brake booster hose (don't drive like that). If it starts up good you know its the idle control valve because you just created a vacuum leak to let air bypass the throttle plate, which is what the IAC is supposed to do.

Another thing to check is your spark plug wires.

-Jon

 

Thanks for the replies.I put the truck on a snap-on scanner today,and it said the tps is out of range.,but that was after i had it running/ideling.i believe this is just another problem.Im going to try and unplug a vac. line in the morning,and see if it makes a diff.
As far as the tps goes,does the TB leak coolant when removed,or does the coolant just pass through it (Throttle Body)?Or is there an easier way to remove the tps(big hammer theory lol).What voltage should it be set at ?
Thanks again,and I will keep you informed to what i find.Chris

 

I'll be surprised if it starts with a large vacuum line disconnected, but I do agree that it sounds like the IAC solenoid/valve. The easiest way I know of to test it is to start the engine cold, and have someone unplug the two wire connector at the IAC solenoid/valve. Normally, this will cause the engine to stall, or at least come close. If you don't notice any difference with it disconnected, the IAC likely needs to be cleaned or replaced.

Take care,
~Chris

 

Well,i tried what ford4ever suggested,and the truck started up fine,and idled.So i replaced the IAC and the truck would start and idle,but idle low.But,the check engine light still came on in the morning, so i bought a tps yesterday,and put it on.The truck runs like a top again.Thanks everyone for all your help.Chris

 

Awesome. I recently used the same trick on a Dodge. The IAC went bad and the truck would die everytime you let off the gas. It was a work truck that had to run and there were no parts stores open at 4 am so i unplugged the pcv vacuum line and ran it like that the rest of the morning with no problems.

-Jon

 

That's killer! I guess I'm still too much of a carburetor man. The idea of an engine starting cold with a large vacuum leak seems backwards, but the proof is in the results. Good call Jon!



Chris- Make sure you reset your ECM! It needs to relearn the parameters of the new sensors!

Take care,
~Chris

 

Whats a carburetor?? My 1992 is usually the oldest thing i work on

Since the idle control valve was stuck closed it wasn't really a large vacuum leak, it was the only air the engine was getting to run! It only works on vehicles with map sensors.

I'm thinking of buying some old carbs to take apart and figure out how they work

-Jon

 

Get a Holley 4 barrel. They're like the Lego of carburetors. I can do them in my sleep. In fact, I think I have.