I have a 2002 pontiac bonneville se 3800 NA. I never see kr in park revving engine to 3000 rpm. I go through all different acceleration/deceleration scenarios. While driving I get kr when my throttle position is above 11%. The kr can go up to 5 and doesn't drop to zero until throttle % is less than 11. I have changed map, maf, fuel injectors, O2 sensors, cleaned throttle body, tested ignition wires and vacuum tested over the last 1.5 years. No codes, no misses and fuel trims are under 5. MPG is poor 20 to 24. A year and a half ago mpg was 27 to 31. I filled with 16 gallons of premium and no difference in frequency and severity of kr. I use torque pro to get data. I don't know what else to do, any advice is appreciated.

You shouldn't see KR unless you are under a load.

What are you seeing for intake temps? High temps in the intake can cause unwanted KR.

I use TP also, but problem is, every time you change a component, you don't reset fuel trims.

Intake temps are very low this week, tops of 35F when I start driving and i got kr with a cold engine. Even after driving a few minutes iat was low at 75F and kr was 3. I did not understand your last line " I use TP also, but problem is, every time you change a component, you don't reset fuel trims. ". Additionally I forgot to mention, in my original post, I also replaced the front trans mount, both front wheel bearings in the last 1.5 years. Thanks.

I'm thinking cold therefore thick air exacerbating some other issue . . . ?

How many miles on the car?

How long have you owned it?

How many miles have you owned it?

Any modifications?

Any trauma?

205,000 miles. I got it with 105,000. I have owned it 6 years. I have put 100,000 miles on the car. No modifications and no trauma. I also changed the spark plugs a year ago, 6 months into mpg drop, using autolite iridium xp606. My fuel pump failed 6 months ago. Warm or cold weather has no effect on kr frequency or severity. My compression test was good all cylinders between 155 and 170. I hope this helps narrow down the problem.

Has it ever had a MAF sensor replaced?

Yes, I bought a denso maf. I also replaced maf, delco.

correction hitachi maf

map was delphi. I also replaced the egr because mine was bad

Coolant or oil in the cylinders can cause a higher than factory spec compression ratio which would simulate a boosted environment. Because you don't know what happened to the engine prior 106,000 miles, its presumed this engine has eaten coolant before.

Long story short, I suggest a rebuild.