Today I seafoamed the engine, worked great, I can actually feel a difference, and would HIGHLY recommend it to anyone, not nearly as much smoke as I expected (was kind of disappointed)

so, so far I have:

seafoamed engine
cleaned throttle body
cleaned maf
replaced 2 vacuum hoses that were leaking
cleaned IACV
checked fuel pressure (fine)
changed plugs/wires


So after all this my idle is about 1000 when the car starts up, then it will go to 700 and idle correctly, when I go to a stop sign and stop the car will still idle at 700, pretty perfectly.

However after about 10 minutes of driving The car will begin to idle funny going from 1100 to 500, then it will get much worse at a stop sign when the brakes are applied, it will bounce around and stall out

All I have left to change is the fuel pressure regulator and the fuel filter (have the kit coming in the mail, thanks spike )

Is there anything I'm forgetting? It seems weird that idle is PERFECT until driving for around 10 or 20 minutes, and then I have issues... Any ideas?

 

That is very weird. Typically when the IAC goes bad the truck just palin wont idle.
When the fuel temp sensor goes bad it wont start when hot.
It could be a leak in the intake plenum gasket.
I am out of ideas right now.
I will have to ponder this for awhile.

 

your idle air controller is picky about being cleaned. i have doen the same with mine and had good results but have been told if you are to clean it dont manually rotate the vane inside, this may cause the baseline that it was used to, to change. also it gets a varying signal from inputs from engine loads like ac, heavy current draw on alternator and ps. it also gets a signal from engine temp, and in your case after having driven for a short while it starts to act up at idle id make sure the temp sensor is a-ok.i would try loading up the motor at idle, like turning on ac,after warm and see if it bumps the idle up lke it should. just a guess.

What yr truck? and there is no fuel pressure regulator in these trucks assuming yours is a Bosch engine?

 

He has a GEMS engine.
If it is not a vacum leak I am leaning towards the IAC.
The ECU must be getting a bad reading from it.

 

ahh yes. well that top end is pretty open, spraying a little gum cutter around the intake should help in finding a vac lk.

 

Ok... never thought about the plenum gasket... i'll spray it up and watch for leaks

i'll also go replaced the IACV as mine was not only gunky but rusty, so something may be up

thanks, i'll let you guys know what happens

 

Make sure that the vacuum line you used for Seafoam is back on tight and not causing a vacuum leak.

 

Tom, You may have already found the problem and realized it. You posted that when applying the brakes the idle gets real bad, does that sound like a vacuum leak to you???