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Discussion Starter #1
07 Cobalt LS, 2.2

At idle engine lopes/surges, occasionally stalls. Does the same when slowing down and coming to a stop at a red light/stop sign. If place it into neutral will stop and run normal. Having AC on seems to make it worse.

Replaced fuel pump 3 years ago.
Replaced throttle body/tps sensor 2 years ago with ac delco brand
Replaced MAP sensor this year
Replaced Fuel Filter this year
replaced plugs last year

At the time I replaced Throttle body was throwing a code for throttle position sensor. Code went away after replacement, but code is back now, along with an o2 sensor and running lean.

Not sure what to do now. Purge canister or MAF sensor?

Anywhere I should start looking next? or replace throttle body again? I guess it's possible I could have gotten a bad one at the time.
 

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well p0102 is maf low voltage, p0121 is throttle body sensor 1 performance, p0171 is fuel system lean. you could be running lean due to the maf not working correctly. if you have a scan tool you can unplug the maf and see if your fuel trims come down to normal range which would indicate the maf not working correctly. smoke test the induction system and exhaust system to insure no leaks anywhere around the o2 sensor,intake and such. stuck open purge valve could cause a lean issue and poor driveability - take it off and see if you can blow through it. with the engine running how it is the throttle body code could just be a side effect. id probably go after the lean issue first. you can always just remove the air snorkel and make sure the tb blade isnt broken or weak
 

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Discussion Starter #5
The code for the MAF sensor just showed up. Never had it before. The tbs has been there since replacing the whole tb. cleared it once, but now back.

I'll check tomorrow if unplugging MAF sensor evens out the loping. Don't have a way to do the smoke induction test. Would be chasing vacuum leaks the old fashioned way.

The run lean has also been there along with the tbs code. Assumed running lean was due to the tb issue.

Along with unplugging MAF sensor, I'll go ahead and clean the tb again.

Also, car has started shifting really hard
 
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