I was having trouble with my 91 TT reving on it's own from 1500 to 2000 revs. The car recently wouldn't start and i thought i'd tracked it down to a cracked and corroded CAS plug. I've since replaced this and cleaned quite a few of the other plugs, but now it revs on its own. It also at first was popping and banging like a rally car and the exhaust was getting too hot to touch, which it didn't do before. My data scan is showing codde 55 - no faults, before it was showing an ignition fault, i think code 21, any ideas?

 

 

I’d disconnect the MAF and see if it does it still.

Check the TPS as well. 

I'll try the Maf in the morning. I unpluggeg the tps, but isn't that high revs not fluctuating revs? I'd also bought a new PTU from CZP in the US, but Fed Ex managed to lose it when it got to Leeds! Hopfully it will turn up in the next couple of days.

On 14/06/2024 at 19:55, Stephen said:

I’d disconnect the MAF and see if it does it still.

Check the TPS as well. 

Yeah, looks like what happens when the MAF isn't connected to me.

A quick update.

Finally got to work on the car today. Started her up and the revs were stuck on 3000 revs, not revving up and down like before. Unplugged the MAF, and the engine just stalled. While looking at this I noticed the throttle was slightly open. I tried to rev it where the cable connects to the throttle bodies, but the cable was tight. Traced it back and found that I had pulled the throttle cable back when I had changed the coil pack and injector connectors. Pulled it back to it's original position put it back in to the bracket, hey presto, sorted.

I have still no idea why the revs were origionally jumping up and down.

Thankyou for the MAF idea that i could rule out, without checking that I probably wouldn't have noticed the throttle.