so i just replaced my PCM and drove the car for like... 200+ miles and one day i let the gas get real low to the point the check gauges light came on. i threw like $10 gas in the tank and the gauge light went off but the dash would still chime like someone was playing with the battery. got the car home and it died... i touched the negative terminal and everything came back on short of the car running. the next day i drove it thinking it was all fixed i get about not even a mile away from home on the expressway and put the pedal to the floor and the speed started slowly dropping but the rpms went over 4500 with absolutely NO pickup. i pulled over shut the car off and turned it back on and drove it back home. when i started it on the way home i got this knocking sound in the engine that wasnt there before... i have no smoke coming out of the pipe, no oil loss, no radiator fluid loss and the fluid has no oil/creamy color. nothing... just knocking it really sounds like theres a rock being shook in a coffee can irregularly. my friend took out the thermostat and said it was bad and said theres a gunk build up on it indicating someone mixed engine coolants. he took off the front valve cover and found no bent rods or bad rockers. the rear valve cover is later tonight. what can cause that knocking if its the only symptom?

Well does it sound diffrent in park/nuetral and drive? if so im going to have to say that your tourque convertor bolts either came loose or came out.Ask me how i know ive been there done that it sucks..lose movememt but no power..

where r they and how do u get to them?

my other question is how does it explain the knocking?

When they are loose it makes an erie knocking sound..because the TC is able to wobble and shake around outside of its normal rotation...They bolt the torque convertor and flywheel together.There is a plastic inspection cover that you need to take off on the bottom of the trans where it meets the engine.Closer to the drivers side of the car.There should be three bolts in there check to make sure they are there and tight!

if that turns out fine it kinda sounds like bad timing to me, why did you replace the pcm in the first place? you may have gotten a bad one

bad timing and bad PCM will cause knocking?

on on older style engine that you can adjust the timing it will have a spark knock, i havent seen a newer one though, i think the only way for that to happen is if something is wrong with the pcm, or icm that would affect the timing

From what I've heard around the forum, the 1994-95 Bonnevilles were (in)famous for having their computers go south. A faulty PCM alone shouldn't cause knocking, but it certainly can cause poor timing and misfiring.

I'm not sure if the PCM controls the transmission on your year, but seeing as how your problem didn't start until you swapped your computer, I'm willing to bet that it does.

my mechanic and i (personal friend) havent went into the tranny yet to check the torque converter bolts. when i did the pcm swap i took my old prom chip out of it and put it in the new pcm... the pcm was pulled from a car in a junk yard. no flashing was needed if u kept the old prom chip. i put the new pcm in and car ran like a champ. and now after 200+ miles it runs like crap...

i wont be able to update u all on the knocking being related to the torque converter bolts untill next week. we pulled the plug wires and 1 of the guts of the wires ripped out. there no thermostat and the altenator is shot so im waiting till i get them replaced to start the car again.