So having more problems with my car, i have an 07 lsj with GMS2, it idles just fine when its cold but when i give it moderate gas it just hits a brick wall and misfires like crazy but once its warm its fine, i always use top quality premium fuel and i just put in new bkr7e plugs gapped to 0.037', any ideas, could it be spark blowout?

 

Update: i changed the gap to 0.035' and am still haveing the same problem

 

Bad coil?

Do you have any codes being thrown?

Do you have an Aeroforce Interceptor or ODB reader to log what is happening?

 

Coils are fine and if they where bad what would the odds of all 4 dieing at the same time, and only when they are cold. The only code being thrown is a general misfire code, i have hooked my scanner up and everything seems fine, i was told it could be my iat sensor but my iats are 4° above ambient so i dont think that would be enough to change it and if i did need to change it i cant find it for the life of me, its not the sensor right after thr TB is it?

 

Can you see if the misfires are on all 4 though?

 

I would assume they are just because litterally when you hit the throttle nothing happens but a machine gun of misfire, the car will not move at all and will just die if you keep throttle in it

 

OK I get it now. I thought it was more of a stumbling misfire.

How long do you have to let it warm up before things get normal?

No backfires from the exhaust? Startup is OK if you don't touch the throttle?

 

It starts up just fine and idles fine until i give it some gas, it has a total misfire until about halfway to operating temp so around 90° and after that until about 150° it will run but kind of surge under heavy throttle like getting hit by a wind gust

 

Well hopefully someone else will chime in.

I have no idea.

I once had something happen like this but it was my CAT getting plugged. It only happened for a few minutes and then the engine cleared the blockage.....Boom!!

Hope someone can help you out.

 

"Missfire under cold acceleration."
Found your problem, let the damn car warm up!

 

Yeah mine runs like crap until you let it warm up too. I let it idle for a few minutes before driving, and drive real easy until coolant is above 150 itherwise i get misfires when im on the gas.

 

I usually wait 5 seconds after it goes to idle rpm or 140F <-- if cold start is done then I start moving. I wait till 181F to do any WOT if I do.

 

it still should run though when its cold still, like GM cant expect everyone to let it idle till its warm, the car should be able to compensate. and i could understand a couple misfires, but this is plain undrivable

 

That is the first legitimate post ive seen you make congrats keep learning

Op you might have a problem but maybe not. Every lsj and lnf ive heard of runs like hell cold. Gm could expect you to warm the car up it is a performance auto not necessarily a grocery getter. For me if I dont let it get to 160 before driving car runs like ****. At what coolant temp are you seeing these misfires?

 

O2 sensor heater? If it weren't working it should throw a code, but maybe it's not right anyways.

I like the "let it warm up" suggestion. Consider it an extra reason to not get on the gas while cold. You shouldn't be doing that anyways.

 

That sounds like a injector seal to me, machine gun misfire is usually injector seal

 

Should i be able to see fuel around the injector then ir do i have to pull the injector and inspect?

 

U probably won't see fuel, I'd say black carbon. When I pulled my injector seal looked normal but there was soot past the seal. First get a scan tool and see what cylinder is misfiring, then pull the injector and look. If I was u I'd just change all the seals to be sure.

 

update: it has got colder and now my IAT's are reading above ambient about 10-12*, would this be enough to affect anything

 

No ur iat will always be above abient temp. Iat1 or 2?

 

iat1

 

It might be a few degrees over ambient... should be that high... do you have a cold air intake?

 

OP figure out what cylinder is misfiring, if its a specific cylinder it will be a good place to start looking (compression/leak down).

And what do you mean by moderate gas? ~50% pedal calling for some boost? I know with my car (LNF not LSJ) I keep it below 50% throttle, 3500rpm, and 1psi until the coolant hits 160.

 

no cold air intake

really anything more than 25% tops, all 4 are misfiring