2002 Alero 3.4 Excessive KR? [Archive] - GrandAmGT.com Forum


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11-19-2009, 11:29 AM
Hey guys, I've been working on my girls car, and I've noticed an excessive amount of KR under part throttle.

A little background, the car is a 2002 Alero, 3.4, 100k miles. About a month ago I removed a clogged up cat, replaced the plugs and wires, and changed the oil. The other night I hooked up my DHP tuner to removed the Cat code from the PCM, and I noticed that while driving, anything over 20% throttle or so I see some KR, up to about 10 degrees at WOT.

Any recommendations on where to look?


11-20-2009, 09:41 AM
Sounds like false knock.

11-20-2009, 09:59 AM
Any typical sources to look into? (Exhaust shields, etc.)


11-20-2009, 05:05 PM
A few people with headers used to get false knock but not everyone, and it hasn't really been a problem with stock cars. I'm thinking there may be some other underlying problem. Cat would be first thing I'd say, but you already changed that so...

How many miles on the fuel filter? Are the MAF and IAT sensors clean? What do her LTFT's look like? Also where does she normally buy gas? She might just need to run some fuel system cleaner and use some higher quality gas if she's been going to a cheap station.