2005 Chevrolet Cobalt Engine doesn't idle

QUICKMOUSE

MEMBER
2005 CHEVROLET COBALT
2.2L
4 CYL
FWD
MANUAL
177,000 MILES

My engine blew a while back and I replaced it with a used engine from an 04 Pontiac Grand Am stating it only had 40k miles on it. After swapping all my Cobalt parts over to accommodate my needs including my old sensors that worked perfectly, I started the car. It fired up first try and immediately died. The car does the same to this day. It only runs if I keep my foot on the throttle and VERY rich. All other driving situations it runs normal. On cold days it struggles to stay running upon start up with my foot on the gas pedal until the coolant level reaches around 90 degrees. Until then it has a bad misfire and backfires through the intake. On a hot day after driving it for a while it runs perfectly normal at idle every now and then. After I fill the tank in any weather it idles high with a misfire. Any help will be appreciated, thank you.

1 Reply

SATURNTECH9

MECHANIC
30,870 POSTS

Heres one problem I dont see the 2004 pontiac grand am as a year and model that says it will work in that car for the engine. I cant tell you why it doesnt give me that info. But for compatibility for the engine long block it doesnt show that engine working for that car. It could really be anything. The intake manifold and exhaust manifold could bolt up like they did but the crankshaft or pistons or even the cam could be different. Just giving examples when ever I try to cross swap a engine or any part I check its compatibility first. Is the car setting any codes in the computer?