So during work a had to drive real slow to look at something out the window and the truck started to do this again. Did it a few times before but this time I was ready with my camera. But it seems to only happen every once in a while. I cant make it do it on command. Doing a search on youtube, I found another vid with a guy with the same problem and fixed it by correction bad wiring on an o2 sensor. On my pickup the front o2 sensor was changed before I got it and was hard wired. (wasnt a OEM product). Think my o2 sensor could be the problem? Heres the Vid>

http://www.youtube.com/watch?v=c4BBbA3xwoc

 

have you gotten the codes read? do a search for the key dance trick and tell us what that check engine light is sayin...

 

Yup, key dance wont work for me. I'll have to wait until I get it to town to get the codes read.

 

Sounds like you have a vacuum leak.
Take the truck to a parts store and get the codes read, I bet it's the IAC. Or it could have something to do with the PCV valve.

 

check out my recent thread "rough idle on cold start.." i have a 2000 2500 with 5.9 and i'm having a similar prob. so far changed out plugs, wires, dist cap, rotor, IAC, TPS, PCV and still have the problem. Next is the pre cat O2 sensor. If that doesn't work then I'm taking it back to dealer for another diagnostic check. Rich.

 

I agree, sounds like the IAC motor whistling in the vid... but his idle speed is about right though :/ . Possible misfiring? When was your last tune up? Get those codes read, im curious.

 

OK, think I might be going into town today (I live 45 miles away) and I'll get the codes ran. Think the best way to do that is go to Oreillys? Dont they do it for free?

My other question is this. Why does it only do it now and then? As you can see in the video, it runs normally I'd say, 80% to 90% of the time.

 

O'reilleys, Advance and Autozone all do it for free.

I know mine does that hissing noise through the air cleaner and the idle bobbles a little bit for about 30 seconds to a minute on a cold start in hot and cold weather and it has since I got the truck. I know it isn't the IAC, TPS, CMP, PCV or a vacuum leak in the manifold or any of the lines since I've replaced all of that and nothing changed it. That's helpful ain't it?

 

Well, the wife vetoed the going to town yesterday so guess I'll get the codes read this afternoon. (that is only if the wife doesn't change her mind again, lol)

 

- the hissing sound is a vacuum leak at the IAC motor housing to TB interface or, at the pintle valve itself which, is not uncommon to hear it when cold. Now, in your case, since it's EXTRA loud AND it runs TOO LOW on RPMs, what's most likely occurring is that the valve is NOT opening far enough thus CHOKING off the air supply THUS why it stalled out on you when giving it more fuel.*


It was already choking itself off and, by giving it more fuel, there wasn't enough air thus throwing the A/F ratio out of whack, thus, it won't burn, thus, it stalled on you.


This IAC motor controls the idle speed at both idle and open throttle conditions so, since you've got a very low RPM speed AND, it was corrected after a restart, this indicates a problem with either the IAC home position or, it's losing control over the motor steps thus pushing the pintle valve into the port too much, thus choking off the air supply. It could also be BINDING as well.*


POSSIBLE ROOT PROBLEMS: either the O-ring that seals the IAC is dry-rotted or, it's not seating into the TB o-ring groove / lip thus allowing air to be sucked in or, you've got a faulty IAC motor that's not driving it to the correct HOME position or, it's very dirty and it's binding.


FIX IS:
remove the negative cable first and wait 30 seconds for power to drain.


Disconnect the IAC harness and all other harnesses for MAP and TPS.


Remove the TB. Inspect for blackened soot like material on the underneath side where, the IAC pintle assembly resides.


Remove the IAC from TB.


Remove the gasket as well.


Clean: using Acetone or suitable solvent and a bristle brush that is solvent compatible. DO NOT USE ACIDs (bad chemical reaction with Al)


Install new gasket and reassemble. Remembering to torque the TB to the proper torque rating to prevent leaking at the gasket interface.


Other possible failure modes:


Vacuum leak behind the intake. There's a white line (hard plastic type) that runs behind the intake down behind the motor on the drivers side down to the tranny. Check that line as well.*


But, remember now, if you HAD a VACUUM LEAK, it would run like that ALL the time and not fix it on a restart. I think, based on the evidence as seen in the video that the problem is rooted at the IAC component level.*


CM