My 1988 Audi 100 Avant (post-revision with RT 5 cyl. engine, non-cat) broke down at the weekend, an hour from home :-( I was going about 20mph when it suddenly splutted and cut out altogether. Tried to restart it but although I could sometimes get it running it would only last a few seconds.
Anyway, have been checking things out today and struggling to determine the problem. It will start from cold [1] but after about 5-10mins it just cuts out. There is no misfiring, but the idle speed gets into a rhythm hunting between 900 & 1300rpm before it packs up.
I've tested the cold start valve and warm up valve as per Haynes manual and they are ok. Throttle body switch appears to work ok. I've bypassed the Fuel pump relay and it makes no difference. I can see the idle stabliser valve moves when the ignition is switched on and it looks clean inside. All vacuum hoses appear to be in good condition and not blocked. The air sensor plate is positioned ok. The diaphragm device near the coil is open circuit. Coil resistance is ok. I get a spark - all plugs, leads & distributor cap are fairly new).
What other tests can I carry out? There seems to be several things that would prevent starting but what would make it cut out? The Haynes talks about a fuel cut-out on the air-box but I can see no connections on it. Haven't checked the voltages at the Ignition control unit as I can't find that either [2]. There are 2 connectors on the bell housing (near driveshaft) - one is speedo I believe, what is the other?
[1] after about 10 seconds cranking but this has always been the case so may be a red herring. [2] It's near the heater blower below the windsceen on my other A100 but not here! Can't see it under the front passenger carpet either.Thanks for any help anyone can offer.
Gary