Mass airflow sensor unplugged idle is fine, plugged in will not idle

SHAWNY321

MEMBER
2007 CHEVROLET COBALT
2.0L
4 CYL
TURBO
2WD
MANUAL
120,000 MILES

I have the SS model supercharged. I installed an engine cold air intake. When I would start my car it would not idle with the sensor plugged in but when it was unplugged it would idle. I checked all the connections on the new intake to see if air was getting in and they are all tight. I also put a new sensor in and the first time I started it the car ran and idle like normal. When I turned it off and put it all back together (never unplugging the sensor again while doing this) and turned the car back on it would not idle again.

1 Reply

STEVE W.

MECHANIC
13,573 POSTS

Remove the "cold" air intake and put it back together as stock and see if it will run then. As you had the battery disconnected it may need to relearn the idle setting. If it idles fine (which it likely will) you have an issue where turbulence in the air intake is causing bad MAF readings. Air leaks before the MAP will not bother it. Check for a vacuum line or intake leak after the MAF.

Here are a couple questions for you to ponder about the cold air intake systems sold these days: Where is one of the hottest areas on a car? Why would you remove an air intake system that pulls actual cold air from outside that area and replace it with an open filter inside that area? The only thing any of the cold air kits really do is open the intake tract to more dirt and noise.