Hi, I hope someone can help me. I have a 2003 Chevrolet Impala LS 3800with 67,000 miles. The car started to run a little sluggish. When I floored it to get on the highway one day it started to break up pretty bad especially after 4000 rpms. I replaced the plugs, wires, module, coil packs, crank sensor, mass air flow meter, both knock sensors, fuel filter and fuel pump. The check engine light finally popped on and shows random misfire on cylinder 1 and 5. WhenI drive with scan tool timing is being removed or retarded quite a bit. My next thoughts are to try the computer???Does anyone have any ideas regarding this demon? Thanks, Art.

 

We have a 2001 and i wrote in with a similar problem. One of the guys had suggested that it sounded like the cat convertor. I have not re-placed it yet because it is not quite bad enough at this pointbut that will be the first place i check! Good Luck!

 

it is possible the ecm is no good but i would try to eliminate the intake manifold gaskets first. It is more common on the 3.4lL V6 but I would do a compression check on those cylindersand compare it ot the others. also check the injectors. they are not easy to get to but stillpossible

 

F.Y.I.I believe thisproblem was corrected by replacing the computer. The reason I am not sure if it was the computer is because the dealer also replaced the cat converter at the same time which both parts happened to be covered undera factory 8 year 80,000 mile warranty on power train control module and cat converter. I usually try to fix it myself and avoid the dealer high pricing but in this caseI would have been better off to go see them in the beginning!!!!!!!