Manager Forum

I'm getting a P0304, P0303, and P0300 stored in memory. The car runs rough at idle, Fuel Trims show bank 1 as -25% and bank 2 as +25%. I have replaced all spark plugs and #4 coil with no change. EGR Valve is functioning correctly with no leakage. No excessive backpressure on either Catalytic converter. Pulled the bank 1 Valve Cover and don't see evidence of broken valve springs or cams out of time. Can't find any vacuum leaks by spraying carb cleaner around intake and vacuum hoses. Brakes don't feel like booster leaking. Test injectors and find all drop approx 15 psi when pulsed. Misfire seems to go away off-idle but car does feel low on power. Any suggestions or ideas would be helpful, my head hurts from banging it against the fender on this car.;

Gary
MAS Auto Center

What are the fuel trims at 2500 rpm?

at 2500 they go to -11 and +13 banks 1 &2 respectively

Is this the set up with the EGR runners in the manifold? I had a van with this engine that I had to tear the intake off of and clean out loose carbon from the ports.

No, that is on the 3.8l. The 3.9 doesn't have the variable intake

Well, typically a vac leak will show better trims at higher rpms, but usually on both sides. Cyl 3 qnd 4 are both on the lean bank, so that makes sense. Could the timing chain have jumped? How many miles on this and how well has it been cared for? No cam crank correlation codes?

No codes for Cam/Crank. #3 and 4 are both on the rich bank which is part of my confusion on this one. Vehicle has about 115k, I have no history on it. I'm suspecting it might be a timing issue.

Oops. Sorry, had it backwards there.

I'd start with mechanical engine first. Basic compression, cam timing etc. Need to see if it's breathing right.

We have had a couple of these in with low compression in one or two cylinders. Definitely check compression.

Tensioner to the secondary timing chain on bank 1 was broken causing cam timing on the exhaust cam to slip a tooth

thanks for posting the fix