Fabio421

89 S4 5 speed. Sat without running for a few years. I had to replace the battery, fuel pump and strainer to get it running. Now that its running the idle is surging badly and the idle is very low. It wont stay running without throttle input. I changed the plugs last night. They smelled of gasoline. There is moisture coming out of the tail pipe but I cant tell if its gas or water that smells of gas. It isn't a ton of moisture but it leaves a stain on the concrete behind the tail pipe. I's well out of practice on working on 928's or cars in general for that matter. Where should I start to look for the problem? The car ran fine when it was parked.

Thanks in advance for your help.

Speedtoys

Might be one or more visciously leaking fuel dampers/regulator under the hood into vacuum lines.

Pull the vac lines from them, smell em.

Mrmerlin

might be a bad MAF,
I would clean the MAF and take it for a drive,
put some techron in the fuel as well as 6 oz of MMO.

Wisconsin Joe

Did you drain the old gas & put new in?

Did you clean the injectors?

I'm going to guess that there wasn't any preservative/stabilizer in the old fuel.

If you've done those, I'll agree with Stan and suggest the MAF next.

worf928

First:
Check the LEDs for the IMS relay.

Suspects:
Bad (old) gas.
Leaky injectors.
Mass-Air Sensor
LH failure.

dr bob

Has the fuel injection brain (LHA) computer been rebuilt yet? Your symptoms point to an age-related failure common to a failing controller. try your contoller in any '87 or newer car to see if th symptoms migrate with the controller. Rebuilt controllers are available from several sources on an exchange or rebulld and return basis.

Fabio421

Thank you for all the responses. Of course I drained the fuel as part of the fuel pump change.

I have a JDS rebuilt MAF on the shelf so I can swap that easily. As for the computer. I have an 85 euro. Any chance I can swap that one onto the S4?

dr bob

Unfortunately the '85 Euro isn't quite the same controller as the S4+ cars.

Speedtoys

If you just unplug the MAF, car should start and idle/run (under 2000rpm and light throttle) "ok".

That would help isolate the MAF question.

Fabio421

UPDATE: Thanks for the assistance gentlemen. The MAF has failed. I haven't replaced it yet but I disconnected it as suggested here and the problem went away. I plugged it back in and the problem came back. Unplugged it again and the problem vanished. Thanks for the help. I'm sure I'll be back to ask for help on something else soon. You guys still rock.