00 WV Bora - Temp and Revs.

the_rovers_one

I have a 00 1.4 bora. The temp gauge jumps up and down all the time. I could be sitting in a car park or driving it shoots up and down.

Tonight the car was acting strange, it wouldn't start, like the battery was dead but started in the end (clock in dash reset to 0:00) the revs start going up by themselves up to 2900. They'd stay there until I put the car into gear, then it was fine!

Any suggestions?

crosstownk

It could be a faulty temperature sender. I've seen the revving thing happen with a couple of Passats of that vintage. Basically, the temp sender was sending erratic signals and the ECU was adjust the revs as a result. I haven't seen the fluctuating temp guage. A dignostic tool will show the temp sender reading while the engine is running.

the_rovers_one

crosstownk wrote: »

It could be a faulty temperature sender. I've seen the revving thing happen with a couple of Passats of that vintage. Basically, the temp sender was sending erratic signals and the ECU was adjust the revs as a result. I haven't seen the fluctuating temp guage. A dignostic tool will show the temp sender reading while the engine is running.

I was thinking it was something small. Felt grand driving. Cheers man.

Moanin

the_rovers_one wrote: »

I have a 00 1.4 bora. The temp gauge jumps up and down all the time. I could be sitting in a car park or driving it shoots up and down.

Tonight the car was acting strange, it wouldn't start, like the battery was dead but started in the end (clock in dash reset to 0:00) the revs start going up by themselves up to 2900. They'd stay there until I put the car into gear, then it was fine!

Any suggestions?

I'd give the throttle body a clean also....

crosstownk

Moanin wrote: »

I'd give the throttle body a clean also....

Agreed - another common cause of poltergeist revving in some VWs. It may also need the throttle angle reset afterwards.

John T Carroll

crosstownk wrote: »

It could be a faulty temperature sender. I've seen the revving thing happen with a couple of Passats of that vintage. Basically, the temp sender was sending erratic signals and the ECU was adjust the revs as a result. I haven't seen the fluctuating temp guage. A dignostic tool will show the temp sender reading while the engine is running.

Would agree with most of the comments, I would be inclined to renew the temperature sender and clean the throttle body. The temperature sender on those models had two channels, one to the temperature gauge, the other, more important channel sends its signal to the ECU, its only this channel that flags a fault code as far as I can recall, I have seen erratic temperature gauges with no effect on driveability but its makes far more sense just to renew the sender and as you are at it, renew the O ring and plastic securing clip as this can become brittle with age.
I have never had to re adapt the throttle body after cleaning it, the engine will run erratically for a few miles/cycles and then return to 750 RPM idling speed if everything is OK including no vacuum leaks due to cracked plastic tubing etc.
One other tip if you are renewing the temperature sender, its far easier and safer to drain down the coolant first, (I know you can whip out one sensor and install the new one if you are familiar with the procedure) there is a drain cock on the bottom left hand (passenger) side of the Rad, just clean this off and you can attach a piece of garden hose and then save the G11 or G12 coolant in a clean container and reuse it, its far better than just refilling with water and then changing to the proper coolant "later".