Well i get a CEL for misfire cylinder 4, and running lean
Also when i pull up to a light it almost stalls rpms are irratic..
it never stalls but it bogs out bad
in drive once in motion it drives and shifts perfect any ideas??

How do you know you're running lean?

If your #4 is misfiring, it's dumping unburned oxygen into the exhaust which could make it appear that way. Check that plug and injector. Maybe swap them with another cylinder to see if the misfire follows it.

2002 Cavalier 2200 5spd

read.. I GET A CEL for running lean.. and cylinder 4 misfire
im thinking intake manifold leak

Sorry, I didn't know if you were getting the CEL for the misfire AND the lean condition or just the misfire. Manifold leaks don't cause lean conditions on FI motors. If you don't believe me, yank the vacuum hose off the brake booster of a healthy car. It will surge, but it won't run lean, nor will it misfire. The ECU will correct for the additional air.

I'm pretty sure the misfire is what causes the lean condition. If your #4 isn't going bang, that means it's dumping raw fuel and more importantly air into the exhaust manifold where it gets picked up by your O2 sensor. Your ECU will try and compensate by giving all the cylinders more fuel, but no matter what, if your #4 isn't burning that fuel, it keeps dumping air into the exhaust making for a lean condition your ECU can never correct. I'd check ignition and the injector.

2002 Cavalier 2200 5spd

hm.. i dont know shop said intake manifold and when i rev it hard it makes a pshh sound almost identical to turbo blow off..lol whn i gas it hard and it shifts it makes that sound..

i dont hear any misfire at all i pulled the plugs looks normal. i rev it all day long and i dont hear it misifire at all.. it must be veryy veryy slight if it is

Did you ever get this fixed. I get the same exact symptoms. thanks.


mtbon

A misfire normally would cause a rich condition. Because fuel isnt being burnt in a particular cylinder. Should also start to smell like rotten eggs because the cat will suck all that up, and start getting damaged from it.

Misfire AND Lean...... I would suggest a good start is checking the fuel injector on that cylinder. See if it's opening. That may be the cause of both right there.

My CEL misfire code went off after a few start ups. The rpm's at idle drop from 1K to 900, 800 and even 700 intermittently. Runs a little rough. At WOT, no problem at all. On the highway at 2K rpms, you can feel it a little bit. How do I test an injector?


mtbon

hey i'm haveing the same problem and i found out that whats causeing my problem is a clogged cat

Can a clogged cat cause a misfire? Not just a #4 misfire, but anywhere? Should I get a cat flow test or just focus on #4 injector?
thanks.


mtbon

yup, clogged cat caused my misfire, i assume from exhaust backing up in the engine and with a weak igntion system it was missing randomly, well after new plugs, coils, housing, and "fixing" the cat i have no more issues. i did notice though when the cat was clogged my intake was exessively loud, maybe again from the back pressure, is yours louder?