Engine power reduced.. Have replace many things.. Still not running right

[Byrk]

I have a 2005 cobalt, base, 2.2, 143,000 miles...

All of a sudden it started running rough.. Would take a while to accelerate.. Didn't seem to want to go above 60.. And when I let off gas and coast into to town.. It goes in engine reduced power mode.. Was misfiring so since it still had factory plugs in it, changed the spark plugs... Didn't fix..

Guy said it may be clogged cat.. Changed out cat.. Didn't fix..

Was getting a p0068 code.. Maf/Map sensor.. Changed out the Maf one.. Didn't fix..

Changed throttle body.. Didn't fix..

Mechanic said it may be something to do with spark.. It was showing 2 and 4 were misfiring.. So we changed out ignition control module.. Didn't fix

Really have no idea what to do next.. Any help would be appreciated.. Thanks

 

[Six0fclubz]

Had a similar problem with mine a while back but with different codes. Turned out to be the emissions air pump and valve that were bad. Replaceing those two solved it. However I never got the P0068 code. Are there any other codes you are/were getting?

 

[roosterk0031]

Tolerated a shudder for 100,000 miles, finally replaced the maf pigtail last weekend and it's been running great. I was getting 101's and 102 most of the time, tried several other MAF with not change (own 3 chevy's with same MAF). I have a Scan Guage 2 and before I finally replace the pigtail I didn't get any MPG or AVE reading that are calcualted from the MAF airflow number.

I did get a few reduced engine power notices, first 2 where when pulling into the garage with a pretty good bump, gravel to concrete. Other was just a average corner. Mine had a little black tape around the pigtail when I removed it and flexed the wires it was better for a while then back to normal.

 

[YelloEye]

I had to replace that pigtail too, was busted right at the connector. Was looking at live data and wiggling the wires when I saw the readings go flat.

 

[roosterk0031]

I don't have ability to data log but was looking at being able to do it. Mine also seem temperature related, acted up more when it was warmer out, once the CEL came on it actually ran pretty well. Initally at 26k when I bought it it it was pretty suttle, almost just like hitting a bump, continuted to get worst till it was bucking at times in lower gears. I just passed 140,000 miles.