When I start in the morning the engine rpm will drop to about 700 and the engine will run rough, it will then go up to 1200 and the cycle will start again. If I put it in gear the stumble will be worse to the point of almost dying. Drive this way for two blocks and all is normal. Only seems to happen on cold starts. I removed the throttle body and cleaned the IAC, and all passages. The IAC had some soot but was not really that dirty. When I started the engine without the air cleaner in place I noticed a lot of intake noise, I suspect it was the IAC in full open position. It lasted for 4-5 seconds and stopped. About a month ago I replaced the plugs, wires, cap & rotor. I had a CEL at that time and replaced an O2 sensor. Have not had a CEL since. I suspect the IAC but have no way of telling without buying a new part. 2000 RAM 1500 with 5.2L. Any ideas from the experts?

 

im not an expert at all. my truck just breaks alot. which o2 sensor did you replace? did the problem start before or after the plugs, wires, cap and rotor? check your tps sensor and map sensor also

 

thats normal.. my truck is a 01 with 48,000 miles on it and it does it when its cold out.. its the choke it runs rough for awhile to warm it up and it'll settle down.. my truck does that about 3 or 4 times now since its 50 or so in the morning.. in the summer it would just do it once to get it going

 

and that air noise you hear with the intake off is normal also.. its air getting sucked around the throttle body flap things when idleing.. when you give it some gas it goes away because the flaps open up a little bit.. thats why with k&n filters you hear engine noise more because you can hear the air getting sucked in.. dont worry about it everything your hearing is fine

 

Wow so it cycles like that when it's cold? Weird. Why not just one long choke cycle? It'd freak me out if that happened too + I hadn't read about it here!

 

yeah its pretty wierd.. well i hope my truck isnt the only one that does it lol

 

Mine was doing the surge thing recently on cold starts too. A new IAC solved it, cold starts are smooth again.

 

Last night I checked for any codes and did not have any. My guess is the intake noise is the IAC going full open and staying there for a few seconds. It then moves to the closed position and causes the engine to go from a lean to rich condition making it surge and stumble. I replaced the plugs, wires, cap & rotor because I had a miss when it rained. The new parts solved that problem. The O2 sensor I replaced was behind the cat. Except for the CEL coming on I could not tell a difference in running quality between the parts. After reading the threads on this site my guess is a bad IAC. I plan to replace it and will post the results.

 

FYI, mine was NOT throwing a code when the IAC went south, just idled like crap.

 

OK, it's been 2 weeks or so of smooth cold starts. This morning the darn thing started surging again!! To a lesser degree than before, maybe 300 rpm's, but still!! Frustrated!