Fuel Woes with my 87 Q. Here is the problem, I start the car, I drive about a mile, come to a stop sign, need to stop of course, put it in 1st, and then 2nd, and can’t go anywhere, that is I can, but only about 15 mph, then after driving like this for a mile or 2, it will regulate itself, and run normal, until I come to a stop again, and the same problem starts all over, it never stalls out, foot all the way down on the floor and still only going 15 mph. I have replaced fuel filter, had fuel lines cleaned, fuses are fine, had pressure tested the pump everything works as it should, any ideas as to what is wrong?

 

Did the problem just happen all of a sudden or did it progress? Since it is an 87Q this rules out automatic transmission.

Does the engine race normally in neutral even if it has no power? Does the problem go away with warm/hot engine?

I would check the following;

Check the fuel distributor to make sure that the plunger and airflow sensor are not sticking.

Check differential pressure regulator, make sure that it is properly set and functioning.

The distributor, knock sensor, ignition ECU, coil sparkplugs, etc. Was the rotor, cap, and ignition wires replaced? If the computer is not advancing you won't have much power.

Is it possible that your brakes are sticking? Will the car roll if you throw it in neutral? I had a problem with my 91 100Q where the rear calipers would stick. The brake proportioning valve has a tendency to rust, I would also check it.

 

Thanks for your reply I appreciate this very much, no it’s not an automatic, yes the engine races in neutral, than slows down, and than idles irregular but will not stall out, yes the problem goes away when warm/hot, fuel distributor is this the same as accumulator?, changed wires recently and plugs, thought this would cure the problem but didn’t, no ONE HERE in my area that could re set the computer! Once it’s warm/hot it runs great.

 

On my '91 100Q I have a similar problem but not as severe as yours. In the morning regardless of the season my car would start normal and idle normally however if I try to pull out it bogs down with no power but idles fine. I have to disengage the clutch once or twice before it clears what ever is choking it. A real pain since I live on a hill. Then the car drives fine without a problem and this symptom is not present when the engine is hot. On this forum I have heard from other owners having similar problems, seems to be a common problem with older Audi's with CIS-III fuel system. I haven't had the time to hook up a bunch of gauges and test equipment to see what is actually happening, since to me it is a minor nuisance and the problem has not progressed in the four years I have had the car. I have tried a different ECU’s, changed the temperature sensor, cleaned/inspected fuel distributor and air flow plate/arm, and checked the injectors for spray pattern, leakage and equal fuel delivery. The only components I have not checked are the system fuel pressure regulator and differential pressure regulator. I suspect the problem probably lies is the differential pressure regulator and or controlling circuit since it plays a major roll in the hot/cold and warm up cycles. Differential pressure regulator has the potential to completely shut off the fuel supply like it is supposed to especially when you are off the throttle and in gear.