410225

91 V8Q When I accelerate, car feels like it is on rubber string, it pulls, pushes, pulls pushes.,... I have changed O2 sensor, FPR, Fuel filter, timing chain, and plugs. What could be causing this?

v8phil

I just did a lot of research about this. If I may, I will just copy and paste what I found and post it here. Sorry for the inconsistancy, I have seperated them as best I can into 3 possible categories:

1)FPR tends to cause a surging under acceleration, not a stutter, a very distinct surge. Flywheel sensors are out.......One doesnt have any effect on the car when its running..... The other will shut the engine down immediately. What it mostly likely is Plug wires. #4 and #8 commonly get moisture intrusion where the wire enters the plug adapter causing them to arc to the valve cover. If you get lucky enough to have the hood open when the car starts doing it at idle you will hear a very distinct "snapping". I've also found wires that are arcing to the wire cover studs. These are harder to hear if you can hear them at all but they have the same symptoms.

2) Your flucuating idle may be related to your ISV (idle stablization valve).....they get clogged and dirty and cannot control the idle as fast as they should depending on engine loading (at idle). It does sound like your partial load "studder" is the same as my "surging".= .=2E..and the fact you have replaced your O2 sensor somewhat confirms my th= oughts....about that not being the cause.....I'm begining to think that the= sutble surging is in fact the computer briefly backing the timing off in a= nticipation of a shift....(ground issue with terminal 51,41 on the Motronic= comp to the trans shift control unit desribed in past posts and some Audi = tech papers desribed in the Archives by a guy in the UK). I also think my issues started after the car got cleaned at the U wash join= t=2E...maybe a short caused by the water in the trans. harness.
3) Mass airflow sensor?...may be worth a look.

Hope that helps,
Phil

rooster 2

You may want to use a water squirt gun to spray on your sparkplug wires to see if any are shorting out. Do it in the dark (best at night), so that you can see any arcing, as well as hear the snapping of the electrical spark.

kaynos

I seem to a similar symptom that occurs both under load and just running in neutral with partial throttle.. Idle is fine, my car will do 700rpm all day long.. If I hit the gas, it has a slight hesistation. The real symptom occurs under very light throttle when driving or just idling. If I rev the engine to say 1500 - 1600 rpm and try and hold the gas pedal in that position, the engine will start surging from idle to 1500 rpm. It will rev up until it hits 1500rpm and then drop to idle and rev back up again immediately.. I press the gas a little more to hold 2000 rpm, it runs steady.