Rough/misfire only during cold start

[STATE6]

Has anyone over on this side have experienced or is currently experiencing rough idle and misfires only during "cat warm up mode"? (The time when you first start the car and your car idle high for 20-30 seconds).

A few months ago while it was still winter in the states my 2011 SIDI V6 camaro started idling very rough during cat warm up mode and threw a few misfire codes. It would come and go and it only happens for 20-30 seconds during cat warm up mode only so I just lived with it. Now it's every time I start the car while the engine is cold. Not sure if is because the weather have warmed up but I don't get any misfire CEL anymore but my cat warm up mode is very very rough still. I checked everything from coils, plugs, vacuum lines, to even doing a compression test. Everything came back normal. I recently had my cat warm up mode turned off by my tuner but I figured this was only band aiding the problem so I decided to have it turned back on and look for the cause.

I been doing some research on this problem and it look as though at least one of every direct injected GM vehicles have had this same or similar problem but I never found anyone come up with an answer except for a few LNF(cobalt SS) guys who said that they noticed the teflon seals would get burned off or just come off completely or purge solenoid valve would go bad causing similar symptoms. Now I haven't checked my purge solenoid valve or my high pressure fuel injectors yet. I really don't think my injectors are faulty because one, it only happens while in cat warm up mode. I can start the engine cold or hot, if I bypass the cat warm up mode this problem does not exist. I would think if I have a leaky injector or teflon seal blown I would have different issues at different times. I could be wrong tho... now the purge solenoid valve..I just found out about this part failing alot a few days ago so this might have to be my next things to check on the list. I am hoping this part is not located under the car tucked in somewhere as I think it is.

Any help from this side would be greatly appreciated!

 

[Hunter SS]

i don't know much about the SIDI engines but what you are describing sound solely like an ECU problem. I'm sure somebody on here will be able to help.

 

[STATE6]

i don't know much about the SIDI engines but what you are describing sound solely like an ECU problem. I'm sure somebody on here will be able to help.

Thanks for trying to help hunter. Faulty ecm crossed my mind once or twice but I really don't think that's it. I get no weird codes and other than this cold start problem my car is fine.

Anyhow, today I got a CEL again. Last time I got an actual CEL was about 2 months ago while the weather was very cold. Got the light for cylinder 5 misfire, then I got misfire history on cy 1, 2, and also multiple misfire. Cleared the code and everything is fine. It only does this crap first morning start or after leaving my car off for a few hours. Just whenever it start in cat warm up mode. This is really driving me nuts.

Come on guys.. over 88 views and only one reply from hunter. Where are you guys with the VE and VZ that was having similar problems? What was the issue?

 

[Hunter SS]

what kind of fuel are you running in it?

 

[SavVYute]

How cold are your winter mornings over there?
Maybe the problem is with the engine temp sensor reading out of range.
Ignition coils can play up in really low temps too, but work fine when warmer.
May be something basic like a blocked/dirty injector.

 

[Travie427]

Yeah mate I have seen that, I used to work for a rental car company and we had 3.0 SIDI Omegas, you'd remember parking the car the previous night and then come the next morning the car runs lumpy like as in the whole car shakes, but then start it up 5 minutes later it runs smooth as. We wrote it off to possibly excess fuel in the cylinders, but even them that doesn't make any real sense. A Holden mech I spoke too said it has to do with the air fuel sensor

 

[STATE6]

Hunter, I been using nothing but the highest we have in the states which is 93 octane. I tried many different top tier gas stations but same results.

Savvyute, only thing that I didn't check are my fuel injector and evap purge solenoid, which I heard both can cause similar symptoms. However, I did try fuel system cleaners and top engine cleaners with no luck. Over where I am at which is maryland, 20 minutes from washington DC, the coldest we got this year is 30* farenheit. It was not that cold at all this year which is very odd.(2012 mayan prediction maybe real?? LOL!)

Travie427, YES!! That is exactly what happens. It could be the first start in the morning or whenever I leave my car off for a few hours and the cat warm up mode(high idle) kicks in. It almost feel like I am cammed for 20-30 seconds, then once the idle come down it's perfect. It seems almost every direct injection vehicles been through this issue once or twice but no one never has answers, not even the dealers. Only answer I heard so far is either normal or something that end up not being.

 

[handtrolley]

From handtrolley. Vic Australia. Only on first start up when motor cold. Misfire, rough uneven idle, wants to cut out. After idle hits normal NO more probs for day. Mine 2008 VE SV6 SIDI UTE. Is driving me crazy. Everyone has diff idea ,cause, solution Thank U