Hi Everyone,

I purchased an Actron 9690 scanner to try and help determine why the more throttle I give the car the less it seems to want to respond. Checked and dialed back timing a bit, replaced plugs and plug wires and the throttle position sensor. Hooked a fuel pressure gauge up and it didn't seem to jump around much when at WOT, but I had it taped too low on the windshield to see the actual #'s - I think it was somewhere north of 30 though. I need to try it again but have someone with me to watch the gauge.

I noticed when the car was at idle the "Knock Sensor" value was all over the place when watching live data on the 9690. I'm having trouble determining if that's normal or not? I forget the average number but it would jump all over the place from around 50 to several hundred. Does anyone know what I should be looking for in regards to a "normal" number for "Knock Sensor" when at idle?

1991 Pontiac Trans Am, 5.0 TPI

 

Check your fuel pressure at idle and then stab the throttle in park and see what they read. Should be 41.5

 

You seem to think the problem with your acceleration has something to do with the information the knock sensor is providing to the ECM.

Have you tried disconnecting the knock sensor, and testing to to see if the absence of knock-sensor data to the ECM produces any change in the symptom?

 

If that is the knock counts it should be zero. The ECM won't retard the spark timing at idle, but if there are counts while moving that will absolutely kill power.

Also, if the injectors haven't ever been replaced they are likely bad. The coils short out preventing the ECM from firing them. But this usually manifests as an engine that is cutting out (on/off/on).

RBob.

 

If you get a new knock sensor ohm it before you install it. RockAuto and other parts stores have sold a member I was helping the wrong sensor. I don’t know the correct part number. From the center pin to the housing it should be 3.9k ohms.

 

I used a Standard KS3T knock sensor. I used it for a 91 TPI setup on a 5.0 Liter. Be sure to measure it at the store, sometimes you get the wrong one in the box. It should read 3.9 Ohms. The TBI uses the KS2T and that will read 100 Ohms but the TPI needs the KS3T. "Tuned Performance" helped with my project. It was a local parts store that sold me the wrong sensor, not Rock Auto.