Hi everyone I'm Johnthan and new to the cobalt family. Well to start things off about a month ago or so I bought a 2008 Chevy cobalt ss/tc from my relative. The car has 120k and is tuned on 23lbs of boost bone stock but that. I'm having a bit of a dilemma now with it. About a day or so I was merging into the highway and I hit about 80% throttle and after the merging it started to act weird. It would not go above vacuum and started sputtering. Today I went to check it and it is having misfires on all 4 cylinders and it lags boost a lot. It's never did this before I heard something about a gms1 but don't know what it is only that it's different maps. How would I know if I have those types of maps on it? Or what to do to the car short answer?

 

First scan for codes. Even if engine light isn't on, can still have pending codes.that would be a good place to start

 

Could be u blew a map sensor or u may have cracked a pipe or intercooler and have a boost leak. Do u still have stock pipes and intercooler? Do a boost leak test

 

P0300-304, P0236 are the only 2 codes

 

Tredstone (I think) charge pipes only upper bottom one hasn't been changed because of the tmap sensor. The upper map had broken but changed it. Can you test them?

 

Well first check that the sensors have the blue sticker on them, those are gms1. I'm not sure how to test them. Something to do with the voltage, someone else may know. But I'd check for boost leaks. Do a boost leak test. See if lower or more common, intercooler end tanks cracked. U can get that out the way and ull have a better idea what's up. If ur leaking, that's probably the issue, but usually u throw a p0101 code for that. But check anyway. Clear other codes as well and try again. Can also pull ur plugs and see how they look. The car could also possibly need it's intake valves cleaned, but first try the other stuff

 

First before any of the map sensor stuff. How old are the plugs and what gap?

 

Plugs are about 1-2 years old they didn't look (bad) they were black. They were gapped at .032 I think

 

How many miles on them? I'm putting my money on you need new plugs, they don't last as long when you're tuned vs stock

 

To be honest man I don't even know. Last I remember he had about 80k on it when he changed them if not more. And it has 121k on it now. Like it builds boost but if I hit 15lb or more after it doesn't want to go above vacuum

 

Black plugs means ur rich, or got oil on them, should be light brownish. If ur boost is not working correctly, u may have an issue with ur wastegate solenoid, mine was leaking and boosted very slowly, like it took me to 6k to hit full boost. I'd take it off and check it to see if it's leaking. Probably would need to get a new one to check that though. But ya black plugs arnt good. But they could also just be carboned up, change them

 

I change my plugs every year, weather they look good or not . Doesn't cost much

 

When I got the car he straight piped it so it would pop a lot when you let off he throttle but the a/f was at 14-15 while cruising, 29.3 when completely off the throttle. They smell oily not like gas. I mean it hits it but I have to mat it almost to reach boost and it creeps up slowly.

 

What plugs do you run? I got the same ones that were in the car they're autolite iridiums gapped at 0.32

 

Get the stock ACDelco plugs

 

that's probably ur problem right there. get acdelco, stock plugs only on this car. at .032 gap like ECaulk says