misfiring S3

[thomsonpop]

Hi All,

I have been having a problem with my S3 for the last couple of months and I think it is getting worse. It misfires for the first five minutes when I take it out. But not always - like when I take it to the garage!!!

It can feel quite severe and sometimes kanagroos down the lane like a bucking bronco. It doesn't seem to matter what gear I'm in. I've had the plugs changed but it made no difference. I've now ordered a new set of leads. A couple of people have suggested it could be a split head gasket which is letting coolant into the CC. Also the coolant level seems to drop very rapidly and I am having the system pressure tested.

Looking back through the paperwork from the previous owners it looks like they have chased this problem before.

Any suggestions or similar experiences?

David

p.s. Apart from that she runs like a dream!

[Roy C]

It could be the Throttle Potentiometer
http://www.tvrsseries.com/throttlepot/throttlepot....

[brow]

I had this problem and went through a similar process it seems.
I decided to remove and clean all connectors relating mainly to the EFI under the bonnet including the air sensor, throttle body, injectors and distributor.
It appeared the dizzy multi pin connector had worked loose.

worth a try, only takes 10mins

[Orophin]

I'm having similar problems with my S3. Only happens at times, when cruising along using small amount of throttle starts jumping. Doesn't happen under hard acceleration though.

[Loubaruch]

I ran an S3 for over 100,000 miles and have recorded my experiences here:

http://bertram-hill.co.uk/tvrs3.aspx

The Throttle Position Sensor (TPS) (potentiometer) and the multiway connectors around the top of the engine are likely culprits but your loss of coolant is worrying. If the head gasket has failed you usually get a creamy emulsion in your radiator.
Best of luck

[thomsonpop]

Hi All,

Thanks for your replies...

Have now had someone look at it. The coolant system has been pressure tested there was a slight leak near the radiator which can be solved so head gasket has been ruled out.

The leads have been changed and the (new) sparkpugs checked and found to be clean.

The problem seems to go away once the car has warmed up and it is also very intermittent which makes me think the throttle pot is not the culprit as this would happen all the time. Drove it from cold this morning and it didn't miss a beat!

When it happens it's not so much a misfire as a complete cut, like fuel starvation. And when it happens the rev counter doesn't drop. I did run the tank dry by mistake a few months ago and wonder if this is the cause. But why would it be so intermittent?