Out of no where> -20% LTFT and steady KR during cruising

[PARKER]

Hello,

During a highway run the other day, I was scanning to see if any changes needed to be made to my GTP due to the drop in temperatures (Canada Fall time) and all of sudden the car goes from operating fine to pulling -20% LTFT and I get KR that rises with the throttle/RPM up to a max and steady 1.93 degrees.

Audibly I heard no pinging, and the car is pretty good at letting me know and I can normally hear even <1 degree of KR.

My first guess was bad O2 sensor setting everything rich so it was pulling fuel (verified by WB reading 16-17:1). So I replaced the O2, and nothing changed.

The only other physical change to the motor was a new supercharger belt that has some slack (compared to old) and now I hear some mechanical noise on the front side of the engine.

So, question is. What do you think of the huge negative LTFTs? And if I am getting FALSE KR from 'possibly' the belt tensioner, would the PCM also react by pulling fuel?

Thanks in advance.

[Dthreap]

Evap probably purged.

[PARKER]

This problem is consistant now; evap purge is temporary correct? short operation.

[Dthreap]

Yeah purge is temporary.

[GeoJB]

Vacuum leak?

This might be a very long shot....
Is it possible something clogged-up the intake filter.

[PARKER]

UPDATE - Lazy fuel pressure regulator, replaced, all better. Combined with dying (although brand new) knock sensor.