So for the last two years now, my truck has had this ongoing issue that happens every once in a great while....it will be running fine, and then for no apparent reason, the idle will increase to about 2500rpm and stay there. When I hit the gas, it starts to sputter and spit, sometimes even stalling out. Lately, I can depend on it to happen at least once a day while driving it, and even though Ive taken it to 3 diff. mechanics...they say they cant find the problem unless they catch it in the act. Ive replaced the Idle Air Control Valve, and capped off the EGR as I was told this could be the problem....but it still does it! If anyone has any info on what this COULD be please let me know, its driving me insane.

If this helps... It is a 1988 Silverado, 350 5.7L (T.B.I. motor)

 

im thinking EGR

 

egr or vacuum

 

It does it at idle most of the time, the truck has done it while driving though. EGR is removed, so its not the EGR. It could be a possible vacuum leak, but the thing I dont understand is, if it were a vacuum leak, wouldnt it do this all the time.

 

I don't know if tbi cars have IAC valves but that DEFINATLY cause me a high idle problem

 

said it was replaced in his first post, I almost missed it too.


don't think the IAC raising the idle would cause it to spit and sputter....




I can't think of anything that could cause that and then go away. even a vacuum leak wouldn't....... what all do you do and it goes away?


maybe a map sensor or the harness for map. causing it to go HI

 

did you reset the IAC valve pisition?

if you don't reset it when you install a new one it will continue a high idle, also try cleaning on your IAC passages

sounds like it coult be EGR related since it only happens occasionally and sputters

could be the timing on the motor also

please explain the symptoms a little more

I.E. what temp, amount of time driving does this occur

check thirdgen.org for more tech articles

 

Temp is always below 200f. Doesnt matter what kind of driving I do, whether its to the gas station right up the road, or Orlando 2 hours away...it does it at complete random. It basically starts as soon as I let go of the gas, the idle stays a little high and sticks for as long as it feels like it. There is nothing I can do to make it go away. If I get back on the gas, it sputters and stalls for a few seconds unless I floor it, then it sounds like its mis-firing all over the place. I havent tried cleaning out the IAC passage though, good idea, Ill let you know.

 

yeah clean out the IAC passage and reset the position

also sounds like the throttle is sticking to me now