idle surging at start

[Dirty S]

2003 tahoe 5.3. 155 *** miles. at start it idles and surges, almost like it was going to stall out. after driving it or warm up it runs fine. the only code i had was a left bank o2 sensor that was replaced and there is no engine light. all fluids, lines and hoses appear good. i did ntice a drip from the exaust pipe.
i recently cleaned the throttlebody and applied seafoam. this also didnt stop the surging. any ideas?

 

[josueh95]

have you tried cleaning the IAC valve? i cleaned mine along with the throttle body and the MAF sensor and i used to have a slightly rough idle after cleaning those three my engine starts instantly and idles perfect 10x better

 

[AZYukon]

its your intake manifold gasket or a vacuum leak, do a smoke test on it disconnect the vacuum line from the brake booster. buy a hose that's the same diameter 3/4 inch i believe and a metal fitting with to male sides ( Home depot or lowes or ace) fitting to connect both. take a rubber glove and seal the throttle body buy a cigar and puff the smoke in to the tube and keep doing it and see if any smoke is coming out from the manifold it self or any of the lines. I did this and found out the my manifold gasket on passengers side was bad. My symptoms was a rough idle when cold rpms would go up and down felt like the truck was chocking or missing gas. hope this helps

 

[VOLZ1207]

Sounds like intake manifold gaskets. I just had to replace mine on my o2. Too much air intake while cold making it surge. Gaskets/intake seal once everything warms up. Mine seemed to do it under 30 degrees. I also changed out my knock sensors while in there. It took me approximately 3 hours from start to finish. I was taking my time as well. There is a great how to video on u-tube that has step by step instructions.

 

[PoppyDenali]

If you don't want to smoke a cigar you could spray some brake kleen around the manifold and see if the idles raises.

 

[Dirty S]

it doesnt seem to be a gasket issue. i went to take the idle air control valve out and seemed confused. its a sealed unit on the passenger side throttlebody with rivets. the iac is not on the driver side. where is it then? i was told this was a flex fuel engine but i dont see anything that makes it diffrent.

thanks uys.

---------- Post added at 04:18 PM ---------- Previous post was at 03:51 PM ----------

well it an electronic throttlebody. no iac to clean. where should i look now to resolve the cold start idle issue?

 

[Fasair]

Mine is doing the same thing, No codes at all. Once it's warm it runs and starts fine.

 

[Doubeleive]

it doesnt seem to be a gasket issue. i went to take the idle air control valve out and seemed confused. its a sealed unit on the passenger side throttlebody with rivets. the iac is not on the driver side. where is it then? i was told this was a flex fuel engine but i dont see anything that makes it diffrent.

thanks uys.

---------- Post added at 04:18 PM ---------- Previous post was at 03:51 PM ----------

well it an electronic throttlebody. no iac to clean. where should i look now to resolve the cold start idle issue?

03 doesn't have a iac, it's integrated into the drive by wire throttle body
I would check fuel pressure first a tester kit is only about $25-30

 

[Fless]

Mine is doing the same thing, No codes at all. Once it's warm it runs and starts fine.

I would recommend doing a TYF search in the appropriate year forum for the same issues.

If you don't find anything in a search, start a thread and be sure to use the correct year forum and provide some specifics about the year, engine size, miles, what work has been done to correct the problem, etc. We have no idea what your vehicle is and its condition.

 

[Doubeleive]

I would recommend doing a TYF search in the appropriate year forum for the same issues.

If you don't find anything in a search, start a thread and be sure to use the correct year forum and provide some specifics about the year, engine size, miles, what work has been done to correct the problem, etc. We have no idea what your vehicle is and its condition.

someone resurrected a 9 year old thread and I didn't catch that, dang