Scotty Solve my Misfire Woes...been working on this car a YEAR now!


2003 Cadillac CTS Misfire 1,3,5

Alrright, here goes....

The vehicle 2003 Cadillac CTS 3.2, I've had a misfire on 1,3,5. Here's all I've done:

New heads, head gaskets, intake gaskets, coils, injectors, crank sensor, cam sensor, throttle body clean, knock sensors, timing kit, timing belt, cleaned pcv system, new fuel filter, name it I've replaced it.

Compression Test: 150 psi all cylinders
Cylinder Leak down test: All less than 15%
Timing marks (used install kit to do the job): Dead on, verified many times and TDC is on compression stroke
Spark: Getting fuel and Spark (verified)

The car misfires @ idle and shakes horribly. The codes that the car throws consistently are P300, P301, P303 and P305 and the Check Engine Light Blinks. If I step on the throttle the blinking check engine light goes away @ 1000 rpms and above. Car drives fine, just horrible misfire at idle.

Ran vacuum test and I'm at 15 inches at idle (Late Ign Timing on Gauge) and when I hold it at 2500 rpms no fluctuation goes to about 18 inches and is smooth. I attached the video of my fuel trims via my scanner. Please help me if you can. Any suggestions?

Comments (4)

Sounds very similar with my recent experiences with my 2005 STS 4.6L. Same issues, been to two shops who can't pin it down. While at the last shop cylinders 1&3 went dead. Still working on things. The bank one camshaft actuator solenoids are suspect, but I think that would affect the whole bank, not just two cylinders. Good luck.



well, I've seen so much bad work done on those engines mechanically, I would at least have a pro engine mechanic check it out fully first, cause that's generally the route of problems on those. I've actually never seen anyone rebuild one correctly here in Houston