mint875000cstq

I get intake backfiring when cold at startup and on acceleration or if I just sit and ram the throttle quickly/repeatedly. What should I be looking for? Ignition? Fuel supply? Air Temp Sensor? Air Filter? Fuel pump is about a year old and fuel filter maybe 6 mo. New O2sensor, new headerpipe/cat. Dist bearings are bad. Thanks , this forum rules!!
-Aaron 1987 5000CSQT 271,000 miles

rooster 2

doing a compression test might pinpoint which cylinder is the problem. You might also want to check to see if the timing is correct...............Rooster

cuatrokoop

The 5kq (non-turbo), with a partially bad exhaust system, would backfire when doing the same thing (playing with the throttle). I agree, check the timing too.

audiqv8

Check for a crack exhaust manifold or leakage in your exhaust system. Outside air is mixing with unburnt gas. Also check to see if all plugs are firing. Backfiring is caused by unburnt gas entering the exhaust system and the heat from the cat and or muffler is causing the unburnt gas to explode.

cuatrokoop

Or just excessive back pressure can cause hiccups...That was my problem.

mint875000cstq

Doesnt the computer on the 5000 turbo automatically regulate the timing? I thought that once the dist. was adjusted close to center that the ECU took over...I would also need to mention that my dist howls very loud when cold (previous post) could a bad dist. shaft cause timing problems? This car is getting too old! I wish I was an Audi Mech.!!! :-D I love this old car!

mint875000cstq

I have exhaust manifold leaks (I pretty sure broken studs and my Head gasket seeps oil...Part of the problem?????
-Aaron

rooster 2

I had that problem. When, I finally had the manifold studs replaced, the head had to be pulled. That's when the mechanic found burned exhaust valves caused by the exhaust leak at the manifold. I should have had the broken studs replaced sooner before it ruined the exhaust valves. I gotta think you are having the same problem. Sorry, but it isn't cheap or easy to repair. ........Rooster

Jon Clay

by the way, sorry to hear that you have it too...

I haven't figured it out, but I think it's got to be related to the fuel distributor. Mine also makes a lot of noise and I've inquired about a rebuild kit for it. Aparently there is one, but I'd rather drive it as is til I can afford to go EFI. I'm hoping that will fix every problem with my car, as I am a believer that CIS is a virus which infects various systems of the car.

Do you think that the "backfire" may be related to the air metering plate being stuck and then popping open? I've wondered about this...

Good luck

Jon