casionerd

iTrader: (3)

Mods are: K&N SRI, ZZP Catless DP, Forge BPV and GMS1 sensors

Cruise on = GMS1, Cruise off = Trifecta tune

Vince tweeked the map about a month ago due to some KR from running 91 octane. Did some various datalogging afterward and he said it looked good. I don't have any gauges to show AFR or anything like that.

Today I got a CEL with multiple codes. The codes are P0300 (misfire), P0303 (misfire cyl 3), P0304 (misfire cyl 4) and P0302 (misfire cyl 2). I guess cyl 1 is the only happy one.

The CEL came on after a cold startup, warm up idle (to about 90 degrees) and then slow driving in a neighborhood.

Haven't been flooring it much and haven't floored it at all in temps under 50 deg. Temps lately have been in the 50s/60s.

Any idea what this could be? I can do some datalogging but I'm afraid to drive it. Vince is on shortened hours and out of town. Not even sure if it even has anything to do with the tune.

Figured with all of the experience on this forum someone may have some ideas/suggestions. Boost will go to and hold at aobut 23psi (tested it for only a moment), so I don't think there's any compression issue. The only thing I've done differently is I got gas (91 oct) with up to 10% ethenol last night. Been using 100% gas until last night but couldn't find a no meth gas station. Maybe bad gas?

Haven't reset the codes and tried running on the GMS1 map.

Car has 23K miles and was bone stock until December.

New to Cobalts and still learning. Any help is appreciated. Thanks.

Edit: Forgot to mention the K&N SRI is at 1230.

donkeyballs

iTrader: (3)

Well first make sure your car is up to temp before driving and 2nd change your plugs.

casionerd

iTrader: (3)

Just changed the plugs. Gonna reset the codes and see how she runs. Here are the old plugs:

donkeyballs

iTrader: (3)

Have vince look at your tune cause those plugs look pretty white but it's hard to tell in the pic. I bet the new plugs will fix the misfires though cause they look beat up lol.

casionerd

iTrader: (3)

Yeah, I thought the plugs looked decent but they looked like they had more than 23K miles on them. After the new plugs no problems so far. Vince has been very helpful and responded late on a Friday night and early on a Saturday morning. He's reviewing the logs as soon as he gets a chance.

I'm kind of thinking it was due to me backing out of the driveway without the car going through the warmup cycle but who knows. Maybe it was shitty 7-11 91oct.

I searched and searched on here. Some say bad O2 or MAF sensor. Doubt it's the O2. I'm catless and since I have that CEL turned off I don't think that sensor has much to do with misfire (if anything). The MAF looks good. May see about cleaning it or getting a new one. There was a little blow by in the intake tube, especially close to the turbo inlet but it all seemed to be just oil. Not much. I don't think the K&N is getting oil on the MAF but who knows. Like I said, I'm new to these cars and not the most knowlegeable guy around.

Don't think it's the coil packs. Hope not as much as they cost. Don't think it's wiring or injectors. Two months ago the dealership supposidly cleaned the carbon buildup in the engine. Not sure where, I'd have to look at the receipt.

Definitely getting a catch can. Maybe MPX (?)

I'm guessing I should pressure test the system, each cylinder, etc. but I don't have the equipment or know how to do that just yet.

Maybe I should Seafoam it or run some kind of injector cleaner through it (?)

Appreciate the help donkeyballs.

Malaclypse

iTrader: (1)

The car will not misfire because of the cat warmup cycle. I'm usually halfway through the warm-up when I start rolling out.

Those plugs are fine and are not likely to cause a misfire.

Your problem could be anything really... but since you didn't have this problem until you got tuned, I'd suspect the tune. Its the most recent thing that has changed.

That and to set a P0300 in addition to three other specific misfire codes by cylinder is pretty rare unless there's an engine mechanical fault or, a tuning issue. Its rare that three coils would just intermittnetly go bad and then start working again, if you follow what I'm saying.

Ch1ck3n

iTrader: (5)

Could be water/contaminants in your fuel somehow.

UltraMagnus86

I have the same problem and the only mods i have are GMS1 and Hahn intake my misfires are in 2 and 3. Ive tried everything to stop it and my compression is 150-160 in all cylinders but the cel keeps coming on every few days.