Engine Loping at Idle - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
Problems and Service Talk about any mechanical problems you are having

 
LinkBack Thread Tools Display Modes
post #1 of 6 (permalink) Old 06-04-2019, 03:31 PM Thread Starter
Newcomer
 
Join Date: Jun 2019
Posts: 4
Engine Loping at Idle

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.
retaliashun is offline  
Sponsored Links
Advertisement
 
post #2 of 6 (permalink) Old 06-05-2019, 06:01 PM
Forum Regular
 
Join Date: Mar 2017
Posts: 53
what is the full dtc list it sets
TCSS07 is offline  
post #3 of 6 (permalink) Old 06-24-2019, 08:49 PM Thread Starter
Newcomer
 
Join Date: Jun 2019
Posts: 4
Quote:
Originally Posted by tcss07 View Post
what is the full dtc list it sets
p0102
p0121
p0171
retaliashun is offline  
 
post #4 of 6 (permalink) Old 06-25-2019, 02:28 PM
Forum Regular
 
Join Date: Mar 2017
Posts: 53
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
TCSS07 is offline  
post #5 of 6 (permalink) Old 06-25-2019, 09:30 PM Thread Starter
Newcomer
 
Join Date: Jun 2019
Posts: 4
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
retaliashun is offline  
post #6 of 6 (permalink) Old 08-04-2019, 11:34 AM
Forum Regular
 
Join Date: Apr 2011
Location: Texas
Posts: 73
I’d start by cleaning the throttle body.
stower17 is offline  
Sponsored Links
Advertisement
 
Reply

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome