04-26-05, 01:49 PM
Alright, so we all knock I'm currently trying to shake down the knock in my car and I'm getting very little success. I pulled the engine codes today, and I get code 21, TPS voltage low at idle, and 44, engine running lean. Obviously running lean is going to cause me to knock, but is the TPS responsible? Obviously I'm going to adjust it back to recommended voltage, but should I suspect there's a clogged jet in the carburetor? Perhaps I should run a can of sea foam through the fuel system?
04-26-05, 02:48 PM
Can anybody check their shop manual and tell me the correct voltage for the TPS? Best I can get is 3.9v at WOT. Everything online says 4.8v at WOT.
04-26-05, 05:39 PM
I'm no mechanic but I do know the TPS malfunctions can really screw up fuel usage, my TPS went bad and the computer thought the gas was always floored. My mileage dropped to 10 mpg highway, so get that thing fixed. i don't know if it's interconnected to the fuel mixture though.
04-30-05, 12:18 AM
I have an '89 and my shop manual says that the TPS should get 5 V (or very close) at WOT.
04-30-05, 06:59 AM
Your TPS sounds like it's no good, that is if the reference voltage is proper. If it's low, the resulting feedback voltage will also be low.
Besides the TPS, I'm assuming you are talking about your '87 with the 307Y motor. If you have a problem with detonation, check the EGR function, timing, CCC functionality, and if everything's okay, you "may" need to do a little "customizing" as follows:
Not sure what year it was but back in the years when I had cars with 307Y engines, I remember having a detonation issue that we just couldn't figure out. At the time, it seems that GM was aware of the issue and there was a "fix". I can't remember if it was spelled out in an actual bulletin or not but the "fix" was to poke a couple small holes in the MAP sensor hose with an ice pick. I seem to recall, they said up to 3 holes was ok. What I did instead was install an aqarium valve (the little valve that controls the bubbles) into the MAP hose and then have someone sit in the car and power-brake it to force the detonation. As they did that, I opened the valve to port off vacuum until the detonation stopped. At that point, I'd lock the valve and glue a little piece of foam to the open port on the valve to filter the air that was being sucked in.
Like I said, this is a "last resort" type of fixe to be used when everything else is known to be operating properly.