Kangarooing down the road when cold..

[Psychobert]

Of late my S3C has been behaving a bit oddly when cold.. My usual routine is to start her up, then while idling take the lid off and get sealed up in layers of fleece before moving off.. Of late however, I've been moving off more rapidly, (not so many layers as its now springtime) and after a hundred yards or so, I get a sudden lurching and kangarooing for a couple of seconds then all is ok. Usually happens round about 1st to 2nd gear change, (slow exit onto the road) but its not related to that I think..

Just had a rolling road check up, mixtures and everything seem fine and it only happens when cold. Can't see anything obviously wrong and flapping around, any ideas? May well have been doing this since I bought it a few months ago but I'd just faffed around enough so it just warmed enough so it got over the hiccup..

[Rhodri_Harris]

Hi Simon

I suffered the same symptoms for a few months last year (had all the engine diagnostics checked, rolling road etc) with apparently no fault. I eventually found that the Throttle Pot was on the way out, not in terms of spikes on the wiper (I checked it out on a scope) but that the track resistance end to end was about 1K, and it should be 4 - 5K. This was upsetting the reference values in the ECU. Finding this cured about 80% of the faults

The other 20% turned out to be the servo vacuum hose was very slightly leaking (only found that after cutting it open and seeing the cracking) and the plenum to rocker cover hose was in the same state.

All of these worked for me so might be a place to start, could just as easily be a HT thing as well though, I'd check out the leads, cap and rotor to check for tracing.

Hope this helps

Rod

[pete_w]

...had similar symptoms but not so severe effects. Find the throttle is a bit 'slow' when cold. Either let the car warm up whilst drinking a coffee or adapt my driving style to compensate.