2006 Chev Cobalt - 2.2L Misfire After Repl Head Gask FIXED

[wagnerautoservice]

I have a cylinder #3 misfire only at idle on a 2006 Chevy Cobalt with a 2.2 liter after replacing the head gasket because it was severly overheated. We have replaced the spark plugs, fuel injector, map sensor. Off idle it runs good and the misfire is gone. We have no vacuum leaks. The cylinder head was pressure tested by a machine shop and was good.

[curtis81]

DID U CHECK THE IGNITION COIL ON THAT CYLINDER?

[jbadenoch]

I assume the machine shop also checked valves and head warpage. Maybe do a running compresion test, that should seperate a mechanical issue from other issue. I'm guessing it wasn't running so well when it came in.

[wagnerautoservice]

I assume the machine shop also checked valves and head warpage. Maybe do a running compresion test, that should seperate a mechanical issue from other issue. I'm guessing it wasn't running so well when it came in.

The head was warped and milled. Can not do a running compression test due to coil pack mounts directly in top of valve cover. Cranking compression was cyl. #1--110, #2--80, #3--60, #4--90.

[wagnerautoservice]

DID U CHECK THE IGNITION COIL ON THAT CYLINDER?

It has a coil pack & it checks Good

[Jeff @ Able Auto]

Cylinder 3 compression very low. I would do a leak down test to see if there was any bleed around the valves or piston.

[steven kiser]

#1--110, #2--80, #3--60, #4--90. there's your rough idle. The heads usually are good for anchors after a bad overheat. I'll be looking for a bit of blow by around the seats.

[ricmorin]

#1--110, #2--80, #3--60, #4--90. there's your rough idle. The heads usually are good for anchors after a bad overheat. I'll be looking for a bit of blow by around the seats.

Agreed. Do a leakdown test on number 3 to see where the blow is going. That'll be your answer.

[steven kiser]

I COULD BE MISTAKEN HERE but this 2.2 is the bastard child of the earlier bomb that was fine until something had to be done to the engine. I would light prayer candles, hire a witch dr, sprinkle it with holy water and hang garlic above the bay door. I see they put a access door for the water pump, i'd like to buy that engineer a beer.

When i worked on this engine after it appeared in the Cavaliers, a somewhat popular vehicle in my area for a while. Overheat = cylinder head replacement. They would warp so bad they would twist 30-50 thousandths. This meant that the cam journals had to be bored or it would snap after a while because of the warpage. The compression is a bit low across the board but the low cylinders are the answer. If a cam was out of time (and it may be) it still wouldn't answer the 60 pounder. I would squirt some oil into the cylinder and take another compression test. If it jumps up significantly pull the plug, the cylinder is either polished or the rings are junk. Now is the time to do some disaster control. If you're not careful you may need a big table and plenty of condiments when you have to eat this. At this point i would suggest a used or new mill. I hope you included a water pump replacement and a radiator. I would bet dinner that within 6 months they're going to pop.

I don't want to lecture and i know i seem to do it but i really want to express the fact that this is a bomb. For some reason these engines will either perform like no tomorrow until the overheat. Then all bets are off and they become frequent fliers and it's all your fault since this all happened after you worked on it. Good Luck..........

[brianp87]

When the head was pressure tested did they check it for warpage? To me all 4 cylinders look low on compression but the 110 psi on is possibly ok. Was the vehcile running when it came in? If so how did it run when cold?

[jbadenoch]

I assume the machine shop also checked valves and head warpage. Maybe do a running compresion test, that should seperate a mechanical issue from other issue. I'm guessing it wasn't running so well when it came in.

The head was warped and milled. Can not do a running compression test due to coil pack mounts directly in top of valve cover. Cranking compression was cyl. #1--110, #2--80, #3--60, #4--90.

Re: 2006 Chev Cobalt - 2.2L Misfire After Replacing Head Gas
by brianp87 on Wed Jun 06, 2012 1:25 pm

When the head was pressure tested did they check it for warpage? To me all 4 cylinders look low on compression but the 110 psi on is possibly ok. Was the vehcile running when it came in? If so how did it run when cold?

[brianp87]

Missed that

[wagnerautoservice]

Complete valve job fixed the miss on idle on the Cobalt. Kind of wierd misfire was only on idle. A reputable machine shop I have used for the last 20 years said he has been seeing wierd problems like this mainly on 3.7 in Jeeps. Thanks for everybody's input it was greatly appreciated.

[steven kiser]

You mean to tell me that the machine shop just milled the head and didn't do the valves? Maybe it's acceptable to some but at my shop i'll not tear a head off and not do a complete valve job. The reason it only was noticed at idle is because off idle the rpm took over by inertia. If you could go fast enough with as less resistance as possible a 8 cylinder with 4 shorted would feel fine.

[jbadenoch]

I hope the machine shop gave you a break on the valve job due to missing that the first time. They should have at least checked em. Glad it's fixed though.

[brianp87]

Ill have the head milled but only after they check it over good. After an overheat im always leary of extra damage and TRY to make it a point to let customer know of this. Im not perfect (far from) but I try to be as upfront about other potential issues with the customers. Seems to me that one is on the machine shop.