delquattro

the bucking is back just as bad as before. This is after I put over two hundred miles on the car this past weekend. When the bucking would surface I would simply swap old relays and problem would disappear for awhile.

When I limped it home tonight I found that I could time the "on" cycle of the bucking phenomenon and accelerate. It seems to be rythmic rather than irregular or erratic. The car idles fine and for the most part can be revved in neutral. It is when it is under load that the bucking starts.

I stopped and bought a can of starting fluid, too - no vacuum leaks. I think I'm going to spring for an accumulator. I can't imagine what else to try.

Whitjr

I had r/r both fuel filters as well. but that didn't stop the bucking.

gmbchef

That is for holding fuel pressure for startup. Have you replaced both fuel filters? I haven't been following this thread that closely.

PJM99

checks the plugs, wires, cap, rotor, fuel filters, air filters, etc. Sounds like that it loses fuel pressure which could be a clogged up fuel filter. Also could be loses spark at higher RPM due to bad ignition components. A clogged up air filter could also choke things up.

delquattro

Yes, all replaced including the ignition coil. Thanks.

delquattro

but, I don't know what else to replace or check and my trusted Audi mechanic is in Denver.

delquattro

while it was idling and nothing happened. I'm glad that fixed it for you. If this doesn't fix it I'm going to have to trailer it to Denver.

austinado16

So it'll take throttle under "no load" conditions, like just sitting there revving, but basically won't take it under load?

And, you don't have any intake vacuum leaks (good).

And, swapping in different fuel pump relays cured it temporarily.

And, all the ignition goodies are new, including the coil wire to the distributor.

I was sort of thinking the engine was rocking to one side and that was pulling the intake boot open causing a vacuum leak that would kill the power, the engine would come back to a resting position, close the crack, start to run right again, then torque to one side and repeat the process.

Any chance it's doing that? With it idling, try pulling and pushing on the intake rubber boot and see what happens. (Rabbits and Jettas, etc, used to do this. They come in with the customer complaint that the car would do it in forward gears but wouldn't do it in reverse. If you'd pull the boot, you see the cracks open up.)

I'd do some checking to see if that's happening, or if it's pulling on anything else.

However, the swapping of the fuel pump relay says something different doesn't it? Like maybe a fuel filter is so plugged that you're only getting spurting fuel pressure? Like there's crap in there that when the pump is running, it's ramming the crap into the filter and the filter plugs. When you stop and take a minute to put in a new relay, the crap settles back down away from the filter media. It then runs good for a little while until the crap is jammed back into the filter.

Have you checked the condition of the "clear" pre-filter? Maybe remove it and bang it out backwards on the driveway and see what comes out. Maybe do the same with the main filter.

Keep us posted, this is a good one!

Whitjr

I didn't find my cracks in the intake boot until I pulled and yanked on it a bit.

delquattro

accumulator and you're all right. It didn't cure it, but it did have an affect. The moments of power loss have tightened up. Even though the cannister fuel filter was replaced in August, I'm going to replace it again. The plastic one was just changed a few weeks ago.

I'm going to re-examine the intake boot, too.

Thanks for all of your input.