cntmaxx

1989 S4 manual with LSD
Car starts every time with no problems, idles fine. On acceleration, in different gears, it "stops accelerating" under throttle - with some jumpiness. Does this most times, not all - I release throttle and try again until it "takes".
I replaced the fuel pump relay but same problem. Could it be weak fuel pump?
Thanks as always for help. Charles

taffelman

Could be the fuel pump or filter, but also condensation in the fuel tank. If I leave my S4 parked for more than 4-5 days I often get condensation trouble (hesitation on hard acceleration), especially if it's been a few rainy days. But the problem goes away by adding a small bottle of anti-condense to the tank (alcohol). If I drive my car daily I never get this problem.

Don't know if condensation is common on the sharks, or why my car is so sensitive to it.

dr bob

Make sure the ignition is up to snuff before you go after fuel system components. Many are driving around with original wires/caps/rotors, and wonder why they get an irregular miss under load. It's really no wonder...

Try the night time firefly test. Open the hood with engine running in the dark. See a little bit of arcing? Fog a little water in there with a spray bottle to simulate driving in humid/rainy conditions. Many people report seeing a miny lightning show. The fix is new wires. buy the pre-assembled Beru set from one of the sponsoring vendors, saves a lot of time and aggravation vs. assembling your old parts onto replacement wire sections.

We did a TB/WP on a local car here a while back, and found caps and rotors that were pretty chewed up inside. Car ran mostly OK in spite of that. New parts are installed.

AO

When you say it stops accelerating, do you mean the the engine or the car?

If you mean the engine, then I agree, it could be fuel related (clogged filter, weak pump, etc), spark related (wired, caps, rotors, plugs) or even something else like MAF, or air filter.

You need to verify all these items to narrow down the list.

BTW, if you meant the car stops accelerating, but the engine continues, it's you clutch.

cntmaxx

Thanks for the direction...
It's the engine that stops accelerating...
I'll look at the ignition stuff as I've had the car since 2005 and haven't replaced these yet.

Jim bailey - 928 International

The fuel tank in the 928 is sealed (one way check valve) and condensation is very unlikely in 4-5 days. I suspect that the humidity is affecting the ignition system.