06 Cobalt Rough Idle/Stall when stopping or quick deceleration

cobaltcruiser

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Ok so heres the solution for all those that are having troule with the engine bogging down or having erratic idleing or stalling when pulling up to a stop sign, red lighjt or traffic.Heres a list to take a look at and from that point forward you will have no more problems. Hell even the 2 garages couldnt figure it out but bu process of elimination on my part I got it fixed and I'm sure for much less considering what the labor fees would have been as well as mark up for the prices of parts just for them ordering and either picking up or having delivered to them.

First I did a full tune up changing plugs aires etc
Than I replaced the fuel Filter
Replaced air filter
Checked all fuses I actually did have 2 blown but one was trunk and other was the lighter
Added a fuel addictive to my gas tank to clean injector and fuel system.
Hooked system to a actron computer scanner but got no returnable codes.
So the next step was to try the throttle body. And once I cleaned it, it once again runs like a dream. Up until the time I gave the air filter housing a good cleaning and cleaned the throttle body it stalled constantly when stopping or even if i let off the gas to go down a hill or coast to any extent.

1. Remove the platic housing that covers the engine and makes it look cleaner. While you have it off give it a good wash since most people havn't touched it since purchase, so why not it only takes 5 minutes.
2. Unclip the wire harness the first being the (MAF mass air flow sensor)
3. you will also notice a small pcv hose connecting the air housing unit to the block. Pinch the clamp closest to the block and pull this small rubber pcv hose free from the block and attached to the filter unit. Check for cracks or rips in the tubing, mine had a tear right under the clamp. replace as needed. I picked up a foot of the pcv hose at advance auto for $1.49 and instead of using the old clamps I picked up 2 new ones for .99 each
4. Loosen the screw holding the hose clamp and pull hose free of the unit.
5. Unclip the 2 clips holding down the air filter housing.
6. Remove the air filter housing and inspect the air filter and replace if needed
7. On the backside (nearest to the firewall you till see a black plastic push pin that needs popped up.( carefully because they break easily and you may have to pick up another one at any auto parts store.
8. After you pop the pin out slightly across from it sticking out from under the air filter housing you will see a tension clamp with a bolt hanging out about even to that plastic clip. Unscrew it a few times to loosen the seal to where the filter housing connects to the throttle body.
9. Lift the Housing unit free of the throttle body if it does not come off freely try loosening the tension on the tension clamp a bit more where its connected to the throttle body.
CONGRATULATIONS----------- The air filter housing assemble is removed from the vehicle.

Now you can get a look at the throttle body. Chances are its build up with carbon and other deposits.
1. Detach the throttle motor connector( The clamp connected to the throttle body)which contains several wires within this connector
2. Theres 4 screws on the throttle body in my case its a 2005 cobalt theres 4 bolts remove all 4 and the throttle body will come right off.
3. While off get a can of Throttle body and air intake cleaner in a spray can. The kind I purchased was made by crc.
4. With the throttle body off the car I liberally sprayed both sides of it with the cleaner and you will see alot of the carbon just run off without touching it, pay close attention to spraying near the butterfly where it attaches to the throttle bottle so that it will move more freely.
5. Get an old rag which can be thrown away when finished. Spray some cleaner on both the rag and the throttle body and wipe off all carbon and grime from the unit. Do the same on both sides, as well as wiping off the the butterfly itself as well.
When finished the throttle body should be shining again as if brand new with no carbon remaining. The last thing i did was sprayed a bunch of cleaner on the rag and gently wipe the inside of where the tthrottle body sits but only about a 1/2 in in I didnt want to go in to far and risk damaging any system.Also once you have the throttle body off there is a gasket which the throttle body sits on, You need to check this for wear, tears, or cracks. and if any replace.
Finally repeat steps Backward to complete inspection, cleaning and repairing of air filter intake system and throttle body.

1. Attach throttle body with the 4 screws.
2. Attach the throttle motor connecter and push firmly onto throttle body
3. Apply first half of housing to the throttle body.
4. Align up housing so that you tighten the tension clamp between the throttle body and the air filter housing unit.
5. reconnect the pcv hose between the filter housing and block.
6. Reconnect the maf wire harness.
7. Put the filter back in whether using the old or a new one. And position the other half of filter housing over the filter and snap back into place using the 2 clamps on it. and lastly slide the big hose back onto air filter and tighten the tension clamp.

That should do it for you. good luck I couldnt find too much info online only speculation as to what to try and everyone gave diffrent suggestions. So I got to work and just started eliminating one thing after the other. And proud to say even with what i di. It only cost me about 85 bux and thats because I did it myself instead of going to a garage and paying the labor fees. because I stopped in 2 diffrent garages and they both said since there were no codes they would have to try a few things themselves anyway and couldnt give me a true estimate. That is when i figured to do it myself. If you need more help than what I gave here feel free to email me at [email protected] its mys wifes addy but the whole family uses it and I never check mine so its easier that way. Or you can pick up a haynes manual #38017 for Chevy cobalts and pontiac G5s 2005 - 2007 all models and it runs about $18 bux but youll have it if you ever have any other issues.
 

jeremyj803

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Thank you cobaltcruiser!

I had these symptoms and followed your directions exactly and now my Cobalt is back to running smooth! Thank you so much for your post!
 

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