ive had this issue for quite awhile now.
first time i start the car evry day, almost every time, it idles rough as hell. almost like it has a cam in it that is WAY to big. it lopes bucks stammers and so on for 3-5 seconds then smooths out finally. then runs normal. ive replaced several sensors and im on my 2nd set of both o2 sensors as well as my 2nd maf sensor. ecm is also tuned but i have a spare ive been running since its cold out(better traction), and still does this. anyone else have this problem?
and just a note, theres nothing leaking as far as i know.

 

do u have cat warmup disabled? i know my car runs like a pos if i blip the gas to cancel the car warmup, these cars hate the cold.

how many KM/miles are on it? could also be carbon buildup, but it think that would show symptoms all the time.

 

Yes I know they do hate the cold!
I had the intake manifold off awhile back and the valves are fairly clean. It does it with either the tuned or stock ECM and only does it when it's really cold out and at first start up. I don't remember if I had the cat warmup removed. Don't think so. My tuner said that was supposed to be on. And yes if I blip the gas it runs normal. Without the high idle .

 

Honestly, kind of sounds normal to me. It does seem like these cars hate cooler weather, especially at start-up. I think people overreact sometimes, or worry too much. It definitely doesn't sound normal to replace sensors for the hell of it. I'm assuming you were throwing CELs (would hope so).

 

It still does the same thing when its warm out?

 

video will helpo

 

Mine does the same with the cold mornings

 

in for vid my car tach needle bounces around a lil but nothing like ur describing.

 

Seriously??? This is normal????? My girlfriend says she had an envoy that did the same thing so who knows...

 

I didnt have my cat warm up disabled with my tune, I know if I tap the gas to cancel it the car runs terrible..exactly how your describing it.

 

if i tap the gas it smooths right out. if i let it run, WITHOUT hitting the gas it runs rough as **** for about 3-5 secons, THEN smooths out.

 

mine did this as well, replaced my purge solenoid in the middle of boston pizza parking lot, and what do you know, its fixed! try that out theyre dirt cheap on ebay.. way cheaper than o2 sensors

 

is that the soleniod on the intake manifold or the side of the purge tank?

 

Intake manifold.

 

i just replaced that a few months back, what are the chances of it being bad?

 

I have the same issue for a over a year and a half now, when its really hot outside its not that bad, when its under 20 celcius it will run like crap for about 3 seconds, even stall, then run good, without blipping the throttle at cat warmup.

With th stock downpipe theres no issue, with the catless it will run weird on cold start, i will try the catwarmup delete soon. Its really cold here right now and it seem to run better... i changed the purge solenoid and it still do the same thing after the pcm relearn the fuel trim.

I changed the front vent valve as well.

 

Hey mike_peperni,
Thanks man!
You saved me a few bucks
Question though... You seem to have less wk done to your car and it runs faster than mine. I have hptuners 22-23psi and regular tires. Maybe it's the radials? And is trifecta worth it? Or should I just stick with hpt and a dyno pull to make it "perfect"?

 

I'm pretty sure that if it is not the EVAP solenoid, that it is one or both of the cam solenoids (phasers..whatever.) On cold mornings, I don't think they oil up very quickly. The Envoy has the same basic setup, so that would explain the similarity. You can maybe try to remove the cam solenoids and clean the screens.

Edit: I've also read that the cold-starts are open-loop, so that could also have something to do with it. I live in an area where it rarely freezes, so I don't see the same kind of issue with my car.

 

Mine always does the same thing when its really cold out as well, i think its pretty much normal..i was not aware that tapping the gas cancelled out the cat warm up. is the cat warm up necessary/functional? i thought that most people disabled that when tuned

 

I got schooled on this not too long ago, lol. The LNF is always in closed loop. Correct me if I'm wrong.

 

I am pretty sure the cold start is open loop.

 

yes cold start is open loop

 

I was thinking about the cam phaser as well until i've put the stock downpipe back on and everything was fine... its a complete mystery, i will test the catwarmup delete and see from there.

TY8425, If your car is well tuned id say keep it the way it is, theres no real benefit to switch unless you want a selectable tune. The radial will help for sure, the launch especially and for 2nd gear as well.
For the mph i gained 2 mph vs stock tires but i also installed the intake and downpipe in same time i have no idea what the difference is, i had 111.5mph with the tune only, stock it was 103.

I will let you know if that solve my problem with the cat warmup delete

 

my car ran like trash after i turned cat warmup off with hptuners... always loaded up when it was below 40 degrees F outside, sometimes when it was around 60. I managed to fix this issue thru my tune and its been running great on cold start for months now. I also noticed that holding the clutch in for a couple seconds for the RPM's to settle and easing it out helps, the extra drag/shock is enough in the mornings to make the car jump from one load cell in the tune to another which causes all sorts of headaches!

 

Yep, sslobalt is right. Basically the only times (aside or a few exceptions) that the lnf is in open loop is during ANY "cold start" situation, briefly during most restarts, and any time the ecm is flashed. Aside from that it's basically always in closed loop during normal running/wot conditions.

OP, if you have any way of monitoring/logging your cam positions I would definitely make sure they are parking correctly when the engine is turned off and also make sure they are moving to the correct commanded positions during a cold start. If they are indeed moving to the commanded positions, then the cam tables are likely setup incorrectly or you do actually have a hardware issue somewhere. Also, get rid of the cat warm-up bs. Personally, I hate it when running a catless dp. If the car is tuned correctly you should have zero issues with cold starts. My car runs e47 (which is nortoriously difficult to cold start) and I have NEVER had any of the "normal" cold start issues people tend to complain about.