So my friend has some awesome equipment to test Hz and other sensor feedback and we looked at the Knock Sensor and the O2 Sensors (much more sensitive than mine as well as had the exact ranges of signal that should be expected). The Knock Sensor and the O2 Sensors both looked slightly out of speck, enough to do a test drive with first the Knock Sensor disconnected and then a drive with both the Knock Sensor as well as the upstream O2 Sensor disconnected.
With the Knock Sensor disconnected the drag or delay in acceleration under load was gone, though it wasn't completely smooth. With both disconnected, it drove really well and there was no drag or delay or alteration of power during driving. I replaced both the Knock Sensor as well as the upstream O2 Sensor and tested the car again. It drives as it should.
So, in the end, the car had these issues:
1) The #1 cylinder had a head gasket leak, fixed with head gaskets replaced.
2) The MAF sensor was sending inaccurate info and had a damaged wire, replaced.
3) The vacuum Transmission Modulator was broken, replaced.
4) The upstream O2 Sensor was not within spec, replaced.
5) The Knock Sensor was sending wildly inaccurate info, replaced.
Interestingly, only item #2 above was determined by the PCM to be in error and would throw a Service Engine Soon light or throw a code, the PCM was silent on the other errors. I guess a 1997 GM PCM was not very sophisticated.
Anyway, thanks for your help!
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Thursday, March 26th, 2020 AT 11:41 AM
