EuroGuy9622

So I've been holding off on this on since I bought the car. I really thought I could solve it myself, as I've been able to with any old EFI-mobile....

I've replaced every sensor deemed relevant to idling. I am 90% sure i've sealed all vacuum leaks. I replaced the idle-air valve with a different one.
Over-all, I feel the car idles much better now. Haven't put many miles on it lately but it has yet to have the loping idle issue.

The persistent problem is starting the car and having it stall out immediately. If I hold the pedal down while starting it will start every time (and stay running). Also, the trend seems to be if it sits for a couple days it will start without assistance. Occasionally it will also start just fine when still hot, so temp doesn't seem to be a factor.

So what is it lacking? Am I giving it primarily more fuel, or air when I'm holding the pedal? I still don't fully understand how this system works. I do have a multi-meter if there is places I can test things.

EuroGuy9622

UPDATE:
I have now also tested the starting-assistance valve. 5th injector...w.e it is called. It clicks. Tried replacing the ground, no difference. Tried powering is directly while cranking. no difference.

When the motor cranks up it is never immediately hitting on all cylinders. I'm wondering if it's a timing issue. I just don't understand why it would have one. The idle has been generally good after fixing the vacuum leaks however sometimes it is slightly high, and when it sits just under 1000 it has a slight disturbance. I am going to install new plugs/wires/cap/rotor but i do not expect this to help.

Rusty Spokes

Your Audi has a K-Jet or CIS injection system. Usually you need some pressure gauges to read out the system and control pressures..and check the function of the warm-up regulator.

Of course..timing has to be spot on and no air leaks at all for the CIS to work correctly.

You don't see that CIS on any cars anymore..but it is a good injection system.

First..check for any air leaks..be certain that the intake..including the manifold gaskets are in good condition.

Ignition timing set to spec..with a timing light

Sensor plate in the air bellows on the fuel distributor is not binding and set to the correct position.

Now you need pressure gauges..what is the cold control pressure and warm control pressures? If the pressures are not correct the car will not run well cold..or maybe not well hot..you need to know the control pressures.

System pressures..you need to know with the gauges..what are they?

Length of time the system holds pressure? you need to know.

If you are certain the timing, sensor plate and intake are perfect..the usual suspect is the warm up regulator..be warned though you can spend some money putting parts on a K-Jet system as a guess.

Here is a pressure kit:Save on S&G Tool Aid 33865 at USA Tool Warehouse Automotive Tools

I don't think you have a KE system..it is the the old CIS with some electronics attached to the fuel distributor and some extras with a control unit. I think that came later than 1988.

Here is a manual for the straight K-Jet system: https://www.google.com/url?sa=t&rct=...0-HdX6hhfcW26A

EuroGuy9622

Rusty... are you an Audi technician? Just curious

My fuel distributor has an electrical connector, don't know why but just some info for ya.
I do like this fuel system, however as much as I curse newer cars, they tell you EXACTLY what the issue is. Only problem there is they can have 500x the issues!

I'll poke around with some of this stuff, at this point I'm becoming less skilled with these specifics but I certainly appreciate all the info. I do still love the car, it is reliable as can be while being almost 30 years old. And it is so fun to drive. I'm considering selling it but that means there won't be any stick shifts at our house!

Rusty Spokes

Many year ago in a galaxy far away I worked for Porsche.

See if you can sort out the fuel pressures. It will be worth the experience.

Thewidowson

Is it only stalling on startup?Audi 90s have a return fuel system.So once the car has been sitting the fuel in the lines will drain back into the tank.You could try priming it twice by turning the key to the position before crank,then off,then position before crank,then all the way on.I would check the vaccum line to the fuel pressure regulator just for giggles.Or the in tank fuel filter on the bottom of the fuel pump.An the normal fuel filter on the passenger side rear.If those filters are excessively clogged it could take fuel longer to reach the engine on first startup.