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88' 80 4-cylinder - I have taken very poor care of this car. But it gets great mileage and gets me where I need to go. It has run rough for quite some time now, but it is getting more noticeable and disconcerting.

It won't start sometimes - thought maybe fuel pump or relay was going, but for a month, no problems. Won't idle - dies pretty much right away if I don't give it gas. When it starts, revs to about 1800 RPM, drops to 1000, then to 600 before kicking back up and starting the cycle over again. From what I read, that may be the idle stabilization valve.

I had a big tear in the air hose (don't know the proper name) between the fuel distribution system and engine, but I repaired that with silicone the other day and think I solved the unmetered air problem. I need to double-check that and other vacuum lines, but I think that's in order now.

But the most recent and most concerning problem is that when I drive the car, the engine surges. It isn't a violent surge, but noticeable. This occurs even when I let of the gas. Today I was going down an incline, let off the gas and applied the brakes (with the car still in gear), but the car still surged forward.

On my list of things to do are general tune-up - clean plugs, new air and fuel filter, but I don't think any of these will appreciably help my problem. Is this symptomatic of a fuel pump going? Idle stabilization valve (which I know next to nothing about) or something else? A mechanic suggested an engine management system fuse problem, but I think I dealt with that once on a VW and that was a really violent surge - barely drivable. Any other ideas?

Sorry the post is so long and rambling. Long days tend to make me long-winded and disjointed.

I have some good ideas from - Ticking noise every revolution, Rough idle post http://www.audi-forums.com/audi-80-90-coupe-forum/40291-ticking-noise-every-revolution-rough-idle.html but looking for further insight.
 

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I can't give you any solid indications as to what is wrong, just some musings around the subject. If the engine is surging quite powerfully then it must be getting more air and fuel, more of one without the other I think will have a detrimental effect on power. I would check the repair to the air hose, check the sealing of the inlet manifold, temperature sensor while you are at it, full throttle switch (if fitted) and wiring to both of these. If anything else occurs to me I will post back again.

Good luck.
 
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