After filling up my 85 IROC today and I looked down at the temp guage and it was pegged ALL THE WAY up! I know the car wasn't overheating, the fan was working as it normally did. I had to get to the dentist (another long story) so I just drove it the 15 or so highway miles to get there. The car ran fine but the guage remained pegged. When I got off the highway and was pulling into the parking lot, the car started to run poorly. It was surging, sputtering and stalled. I was running late so I just parked it and went in. I came out an hour later and cycled the key a few times (it was still pegged) and the guage came back to normal. I opened the hood and giggled the connector on the left cylinder head. I also checked to make sure that I had put the gas cap on correctly. I got a loud wooshing noise when I took the cap off. Is that normal? I drove it 25 miles home with 0 problems. I checked the connector at the coolant switch and it seems ok. I thought that that sensor only ran the guage and wouldnt make the car run poorly. I am at a loss as to what could have happened. Anyone?

 

The them sender for the gage has no effect on the engine.

 

put some dielectric grease on the temp gauge term

check your fuel tank vent if you have excessive preasure

 

Temp sensor may be getting ready to fail. The sensor is a variable resistor. It grounds the gauge through the resistor. The cooler the engine the more resistance. As the engine warms up the resistance drops. You can test it by taking the wire off the sensor and jumpering it to ground with the key off. Turn the key switch on and the temp gauge should peg. If it pegs when you short it to ground, then dielectric grease won't fix anything because you don't have a loose or bad connection, you have a sensor that is intermittantly shorting out to ground.

 

How exactly would I do that. Sorry, guys these cars are new to me. Been into VWs for quite awhile!

 

I think it is normal to have fuel pressure build up a bit in the tank. I have a 1987 T/A, my wife has a 2000 Saturn, and I have a 2004 Dakota for a daily driver. All three vehicles build up pressure in the tank. I think it is part of the evaporative emmission control system.

 

Yeah I figured some was OK, but it just seemed like a lot. Probably more of me being paranoid than a problem with the car. I've driven about 75 miles and its run like a champ! I tried to get codes out of the ECM and it didn't flash at all. Maybe the ECM is flaking out on me, I have a spare so I will just have to see if it happens again.

 

symptom: temp gauge way up, AND brake light is on.

this happens to my car kind of frequently. it's a problem with the ignition key switch mechanicals, maybe getting old, i'd guess not the lock cylinder itself. when in this mode, it seems to be hung up just a bit between the "start" and "run" key positions.

for my car at least, i've found that even while driving, i can gently ease the key back towards the "run" position and you'll hear a click as it snaps to it's normal position, and then the temp gauge immediately goes to normal and the brake light goes off. i think some contact in the switch or steering column is inadvertently grounded out in this limbo mode.

first time this happened to me, i damn near had a cow cause i thought my motor was toast. even when overheated and died, i've NEVER seen the temp gauge pegged off the scale.

i haven't busted out the wiring diagram yet to see where those two signals come together, and what they have in common with the ignition key switch. one of these days, the elusive round tuit.