06ssgm2

ok i've read some threads first before posting to see if i could find anythin out. a little help just not what im lookin for lol. ok so here goes i have a 2.85 pulley, 60# seimen flow matched injectors, full exhaust 4-1 ca header, 2.5" ca catless downpipe, and a gmpp catback. aswell as a injen cai and some other minor things. i ordered a tuned ecu from zzp askin for certain things i wanted done to it before sendin it to me. includes 7300 redline, 2.8 pulley, fans earlier, and all my mods tuned to it ect.. everythin went together fine and started right up after a couple kicks. the problem im havin is at idle there is a miss in the motor. even a P0300 random cylinder misfire code comes on once in awhile. now when im drivin WOT or normal it drives fine. its only when i come to a stop, ect. and has even stalled on me once. you can hear it in the exhaust and see the motor shake. the wierd thing is if i turn on my a/c it completly stops. i guess the belts spinning faster plus a higher idle idk. their are brand new ngk copper plugs put in it, gapped at .035, brand new oil change, fuel filter, brakes, and even supercharger oil changed out. maintence 101 lol gotta do it... now i've trial and errored every possible thing on the car i can, before i say its in the tune itself. but the thing is should a 2.8 pulley that its tuned for to a 2.85 sc pulley make that much of a difference within the tune. i'm changin the pulley when it gets to my house, but dont think its gonna do anythin different. now zzp's solution was to send my stock ecu in and have them reflash that one with hpt. if its gonna be the same tune why would that make a difference. they also want me to figure out my fuel trims at idle, 30 mph, and 55 mph. since i dont have a tech 2 or so forth thats a little hard to come up with.. please guys any info you can give to me would be a great benefit.. i just dont want it to blow up or somethin of the sort.. help lol?? thanks

rockkrawler628

good luck man... sorry to hear that, thats why i ended up not getting a canned tune. I just went with stage 3... good enough for me and **** the A/C

jekqmb

Hmmmm i had the same problem, soon to find out my TB had a ton of carbon build up in it. I mean the exact same problems your having, check your TB out and clean it.

06ssgm2

Yeah just did all that too: new air filter and the throttle body was cleaned less then a month ago so it should be ok checked it yesterday looked fine..

When you cleaned it out or if you did, did it seem to stop the problem or is it still persiting??

jekqmb

It helped it, the frequency on your MAF might need to be changed.....I know this is something guys do when tuning their cars and they have IDLE surge, also it may be a junk fuel filter.

RG4

bump

06ssgm2

dont kno for sure on the filter looked ok.. but as for the retunin of the MAF i dont live near anyone that i kno of with hpt so that doesnt help to much, anyone kno of one?? plus what i keep hearin and zzp said this to me aswell that when you change out your intake system the sensor reads more airflow cause of the bigger diameter of the tubin.. duh but ive had a cold air on there for awhile when i had gmstg2/ hpt tuned.. dont see why now they think it may be causin it to mess up..

jekqmb

That is where the MAF reading comes into play that i was talking about, haha.....Im betting thats what it is.

Area47

so, i didn't follow anything in that post. my head hurts. what is the issue.

RG4

pretty much . he throws p300 . it mutiple misfires. the car only does it at idles. also the cars revs jumps up and down when stoping ..

Area47

change plugs.

300 code could be from multiple things.

these are simple fixes actually.

sehoublackss

I'm having the same problem.

https://www.cobaltss.net/forums/problems-service-maintenance-69/car-dealer-misfire-idle-108543/



.

Joeyavhu

Mine has the same issue, only much worse it seems

https://www.cobaltss.net/forums/problems-service-maintenance-69/severe-misfires-78802/

I have tried SO MUCH. Trust me. People will tell you change the plugs, check the cat, check compression, check intake (because of the surge), check the injectors, check your EGR valve, clean your TB, clean your SC rotors....

Anyway, non of that worked for me. My next thought is that it is running too rich at idle. I know it already runs rich, and this car is hard to tune with such big injectors at idle, so, once I put my buddies Wideband in hopefully I can find out a little.

racehtecobalt

no,no,no......the miss fire is caused do to the fact that you are actually making your car run lean..like this............do this and you will see what i am talking about.......pit your car in first gear at around 5 grand and punch it...bang the limiter 2 to 3 time ....wait a few seconds and your check engine will flash........this is a miss fire...your forceing in air faster than what your engine can pump gas into the piston which causes a bad air fuel ratio to occur and thow a check engine light ..

in other words your running lean.....