99 Dodge ram 1500 4x4 , 240,000KM (150,000miles)

Recent work:

- New cat
- New Post cat (Downstream) O2 sensor
- Plenum and other intake gaskets replaced
- Pulled and thoroughly cleaned IAC
- New plugs, wires, cap, rotor

When first started up after sitting for 8+ hours (Overnight) it runs fine for about 1-2 minutes, but when it starts to come off of fast idle and settle into its normal idle the engine starts to sputter and sound like its going to die.

When the engine eventually settles into its normal warm idle, about 30 seconds later, the engine normalizes and the bad idle goes away.

When the engine is at running temperature this issue never happens.

Ive tried multiple things at the advice of mechanics, and the people here at DF.

Ive pulled my IAC, it was horribly filthy, I cleaned it good with throttle body cleaner - This did absolutely nothing, not even the slightest improvement...Should I try replacing it anyways?

Im not throwing any CEL's so I think my Pre-cat O2 is good. The Post cat O2 is brand new....Would rather not spend $100 on an O2 sensor if its not going to help...

Complete spark plug job has been performed.

Plenum replaced..


Can anyone help? Im ready to give up on this...

Thank you.

 

my truck acts the same way. will actually idle at about 200 rpm and almost die, then back to normal a min or 2 later. been like this for years. full tune up, new exhaust, new cat, o2 sensors etc etc etc. still there. the only repair i know i need that i havent doen is that plenum gasket. maybe its got something to do with it?

 

Doubt it, because I have replaced mine and it made no difference.

 

i'd replace the IAC. the little sob's are troublesome. you can get one at any parts store in the $40-50 range.

be sure the TB well is clean and the little port in the end is open. don't push, pull, or twist the pintle on the new one, and reset the pcm when you install.

 

Maybe tps reading goofy?

 

How is the PCM reset?

 

Disconnect the battery while you are cleaning the TB. That should be adequate to the task.

 

Thanks gents. Ill give that a try.


...You really think though a new IAC could help? as cleaning mine did nothing at all?

 

You can test the IAC motor. sort of...... Take off the air filter housing, look down the TB, and see where the IAC is currently sitting. (should be at least partially open......) Disconnect the battery for a few minutes, to reset the PCM. Hook it back up, and have a friend turn the ignition to On. IAC motor should cycle shut, and then back out a bit. If it doesn't move at all, or, if it closes, and stays there.... its probably bad.