Strange things happening?

[shaggman1]

I put this post in the newbie forum but I didn't get any responses. I thought maybe I would try it in here. Thanks guys.

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I am wandering if anyone can help me? I now have a pocketlogger and can watch what is going on a little closer.
I am getting a voltage spike up to around 17-18volts while the car is running. when this happens all of the dash lights get brighter and the RPM's slow down just a little. Does my 92 TSI have a voltage regulator that can be easily replaced? I am also getting a constant 3.49volts out of my front O2 sensor. And here is the real kicker, when I check the error code, I am getting a knock sensor code. Even before the engine has been started?
Is there a common circuit between these things that could be causing a problem? The only thing that I have done to this car is remove an aftermarket alarm system from way back that was nested under the dash like a parasite.

Does anyone have any ideas? I would really appreciate your help.

Thanks,
Rick

 

[my_gst95]

You had better replace your alternator or check for shorts before you destroy your bulbs, fuses, and relays! I have a 2g o2 housing on my 1g and the damn sensor points to the alternator. Well one night, the ground screw on the alternator backed out and made contact with the o2 sensor! Like you said but worse, all my guage clusters got bright for 5 minutes of driving (18-19v) then POOF!, all my headlights, tailights, and some cabin bulbs...all busted! Had to replace all the bulbs, 1 eprom ECU, 3 relays, and the headlights (which are a PITA to replace on 90-91's).

The knocksensor is probably bad. The ECU will save the error code til its fixed, replaced, or you turn it off on the logger. Feel where the knock sensor is and if the black puddy has already melted off. Either way, I would just replace it.

Good luck,

my_Gst95

 

[shaggman1]

. Feel where the knock sensor is
my_Gst95

Where would the knock sensor be?

I did also find a frayed wire coming out of the o2 wire harness today!!! It doesn't appear to go to anything... Motor swaps, gotta love'm.

 

[my_gst95]

The knock sensor is at the back of the block, around where cylinder #2 is, about 3" under the bottom of the intake manifold. Kinda tricky to access if you have your A/C and intake mani bracket in, but you should be able to reach it by removing the battery and tray and reaching under.

my_gst95

 

[shaggman1]

So, the voltage regulator is in the alternator? I was not sure about that. I will get out and buy a new alternator before driving it much more. I am not sure if my datalogger can turn off the knock sensor or not but I will be getting a new one of those as well if it is bad. This car got a motor swap a while back before I got it (92 motor for 93 motor) and everything seems to be done right but I am finding out that there were so many small changes made to these cars over the years that it could possibly have the wrong O2 sensor in it all together. Thanks for all your help. I will be using the next couple of warm days to get under the hood and figure things out. I'll let ya know.................


Rick

 

[shaggman1]

Wow, I found something really weird today. I started my car and let it run for a few minutes to warm it up and let the O2 sensor warm up. I then thought I would unplug the front O2 sensor, (the one reading a constant 3.49 volts) and see if the voltage changed. It turns out that when I unpluged the front O2 sensor the logger showed no voltage on the rear o2 sensor and the front sensor stayed at 3.49 volts. Is it possible that the logger has the two sensors mixed up or are the wires in my car mixed up? I am using the MMCD palm datalogger. I would hate to have to rerun and rewire most all of my engine harness but it is looking more and more like that is where I am headed.