I have a an 87 CS, and it's giving me some real trouble right now. Before, it had a problem starting. I'd have to start it 3 or more times before it would keep running. Then, this problem mysteriously disapeared. The car now starts fine. Great right? Wrong, because now it stalls often, doesn't idle without a good tap on the gas every coupla seconds, and what's worse, when the engine is hot, it won't start again. This is a great combination of problems because it often leaves me looking like an *** in the middle of traffic, pushing my poor ol' car down the median until I can get to the nearest parking lot.
The idling problem shakes down like this: sometimes, when i've been driving for a while, the sky is bright blue, the barometric pressure is perfectly right and i haven't done anything to offend the good lord for a while, it idles perfectly. Usually though, i'll be sitting at the stoplight with my foot off the accelerator, and for no apparent reason, engine speed jumps up to 3000 rpms. Then, if i don't get a shot of gas at it right away, it cuts right out, and i'm stuck at a green light with 8 hicks in old ram chargers(great vehicle) or new S10 Extremes(worst vehicle ever made, save for the PT cruiser) road-raging behind me, because as i said before, it's got that little hot starting problem. Anyway, if anybody out there can give me any ideas, it would be much appreciated, since i'm a poor college kid who doesn't really feel like coughing up next semester's book money to the local foreign car shop, which happens to be booked solid for a month anyway. Thanks for any help you can give!

 

for hot start problems...
electric fuel pump not working
engine air intake system, leaking
system pressure outside tolerance
injectors leaking
idle stablization defective

check your hoses closely to make sure theres no cracks near your isv or any other vacuum hoses. If there is a hairline crack, is would be speratic. If you have a turbo, check out the intercooler hose bottomside.
then if all else fails, check your system pressure to see if maybe your injectors are leaking. Hope this helps.

 

Also, try unplugging the brain box. A friend of mine tried this when his '87 4kcsq was acting up, and it does perfectly ever since.

 

and it goes a little something like this....hit it!

1.I had no power at the idle stabilizer. (no fuse for the little black box)

2.I had a faulty differential fuel pressure regulator going out. (sporadically no start= no fuel pressure) very expensive, you now that little grey sucker at the front of the fuel distributor

Good Luck. Thankfully the Bently walked me through this

 

do you know what the best way to get at the computer is? would pullin the relay have the same affect? i tried that and it didn't do much.

 

The computer should be(correct me if I'm wrong) in the scuttle with the wiper motor.

 

The CPU is to the right of the glove box. Pull the box, and voila.

 

I have an '87 Quattro and a PT Cruiser and they are both great cars for their intended purpose.