Ok, my truck started doing this randomly and of course never when I am near a shop. Sitting there idling truck can be in park or drive it will begin to idle down... 700 rpm 500 rpm 300 rpm you can smell the exhaust, and the whole truck shakes while it is doing it and you can hear it sucking in air under the hood, it will go up and down until it finally dies and you shut the key off then start it right back up and it is fine sometimes for days or weeks or sometimes for 5 minutes I have taken it to numerous shops no one can even give me an idea of what it might be. I have replaced the sensors on the throttle body and no change. Every now and then it will correct itself and the idle will jump up and be fine for a bit then start again...at a stoplight waiting for the light it started doing it and got down to like 300 rpm and fixed itself my idle jumped up to 2000 rpm and the dam truck almost took off into traffic I slapped it into neutral and it idled down to normal. Anyone got any ideas????

 

You've changed the IAC motor? I could see that causing a low idle stall, but I don't thing it could shove enough air through to rev 2k RPMs. Have you tested fuel pressure?

 

Yes changed the IAC twice. the mechanic said the fuel pressure was good when he checked it but of course, it wasn't acting up at the time he checked it. Whatever is causing the problem is causing the engine to suck in huge amounts of air as it starts to idlle down and chug and you can really smell the exhaust. I am going to take it in and have the throttle body cleaned and see if that helps. I have had the truck about 3 or 4 years I did a tune up when I got it how often is it recommended to do tune ups on these?

 

30K miles or so.....