turboglenn
15+ Year Contributor
- 6,375
- 123
- Nov 5, 2007
-
RIpley,
West Virginia
Well, lately My J&S had been showing anywhere from 4 to 10 degrees of timing getting pulled on mid throttle lower boost accelaration about every 3rd time i get in it even slightly. I've been afraid that the motor is about to go, but every time i get on it WOT and accell from a lower RPM there's no more knock than normal (usually none) Then about 2 days ago it hit me. The AC compressor is on the KS side of the block and firmly attached enough to transfer plenty of noise if it were making any, so i began doing back to back pulls at anywhere from 30% to 70% throttle and what i found was surprising.
My AC compressor is causing my bad-ass J&S with filters applied to it go off like the motor is flying apart. Sometimes it will even do it a few seconds after the compressor has told to dissengage (within 1-2 seconds i would guess) I mean there have been times lately where i'm in a parking lot doing 3500 RPM in 1st gear when all the sudden i give it a little gas and i get 10* pulled out immediately and the car falls on it's face, even on light smooth accell at about 40% TPS and 10-12psi i have gotten crazy amounts of knock picked up by the J&S.
There's no real point or great enlightenment about this thread, but I have proved that an AC compressor can register faulty knock to even the most sophisticated knock sensing equipment... Might want to check yours out if you have major PK issues. Since the pulley will be spinning even if the A/C is off, you may have to pull the belt to be absolutely sure if you're picking up any noise from the A/C compressor or not.
What really got me to looking for a more underlying cause than actual engine damage is that the knock was picked up so "evenly" across the motor. The J&S senses and retards on an individual cylinder basis and usually when i'm knocking it's cylinder #3 that starts and maybe # 1 or 2 will follow with a little less knock (read out is on the dash) When getting this PK lately it's showing that all 4 cylinders are knocking equally and to a large extent, because this is a very uncommon way for a motor to knock (all cylinders at once) I bascally knew there had to be something wrong besides actuall knock and thank God I was right
I mean i am only waiting on new pistons and to get my spare motor bored and put together, but i don't want to shell this one in the mean time, a spare does you no good with a hole in the side of it. And that was what i was starting to fear with the readings i was getting
My AC compressor is causing my bad-ass J&S with filters applied to it go off like the motor is flying apart. Sometimes it will even do it a few seconds after the compressor has told to dissengage (within 1-2 seconds i would guess) I mean there have been times lately where i'm in a parking lot doing 3500 RPM in 1st gear when all the sudden i give it a little gas and i get 10* pulled out immediately and the car falls on it's face, even on light smooth accell at about 40% TPS and 10-12psi i have gotten crazy amounts of knock picked up by the J&S.
There's no real point or great enlightenment about this thread, but I have proved that an AC compressor can register faulty knock to even the most sophisticated knock sensing equipment... Might want to check yours out if you have major PK issues. Since the pulley will be spinning even if the A/C is off, you may have to pull the belt to be absolutely sure if you're picking up any noise from the A/C compressor or not.
What really got me to looking for a more underlying cause than actual engine damage is that the knock was picked up so "evenly" across the motor. The J&S senses and retards on an individual cylinder basis and usually when i'm knocking it's cylinder #3 that starts and maybe # 1 or 2 will follow with a little less knock (read out is on the dash) When getting this PK lately it's showing that all 4 cylinders are knocking equally and to a large extent, because this is a very uncommon way for a motor to knock (all cylinders at once) I bascally knew there had to be something wrong besides actuall knock and thank God I was right
I mean i am only waiting on new pistons and to get my spare motor bored and put together, but i don't want to shell this one in the mean time, a spare does you no good with a hole in the side of it. And that was what i was starting to fear with the readings i was getting
If the car ever gets to where i can't run the AC during the hot Nebraska days, then it's time to start working backwards and taking parts off haha.
