Wont idle but runs fine with throttle pressed

[jbanderson]

Truck just all the sudden started this yesterday. It will semm to run really rich as if it has a choke on the motor or something only at idle.
I Thought it was the IAC so i replaced that. No change. i cleaned the maf and still nothing. TPS maybe? Can I check that?

 

[jbanderson]

Anyone?

 

[jhammel85]

I would check for codes and check for vacuum leaks. There are alot of things that control idle....Another thing to try would be to test the TPS sensor. Probe the ground wire and the middle wire of the TPS and with the key on but engine off, move the throttle. Should be nice and smooth

 

[jbanderson]

no vacume leaks, Its will go from 2100.... to 1000 then drop to 500 and barly stay running or die. then it will crank right back up.

 

[Nhaz]

Have you tested the IAC to confirm that the computer is telling or not telling the IAC to function?

Have you checked for vacuum leaks?

 

[jbanderson]

No I havent checked to see if the computer is working the IAC.. I guess I could search i duno how to do that.

I havent checked for vacume leaks because at first it was an intermittent problem and a vaccume leak would have been consistant i would think.

 

[Nhaz]

Check the vacuum tube elbow that goes into the brake booster. Its a point that has problems and can be intermittent.

Another spot is the vacuum tree on the intake manifold. A lot of them have a spare hook up location for another vacuum line. The spare is capped but the cap is just basic rubber and can get hard/crack or just get blown off sometimes.

If that doesn't help then use the old propane tank trick to check for other leaks. Its easy to do and is a good indication is you actually have a problem with a vacuum leak or not.

 

[jbanderson]

thanks Nahz.
I fell like an idiot... it was the cap on the back of the intake on that Elbow thing that has about 5 vacume lines running to it. one was off and had nothing on it... So simple.... runs like a champ!!!

thanks everyone!!