Audi 5000 turbo quattro issues...
 

Hey guys,

My buddy has an '87 5000 turbo quattro that has some goofy issues. It runs great when it is cold, but not so great when hot. It has some hesitation and backfiring when you rev it from idle. Once about 1500-2000 rpm, it's fine. We've played with the ignition timing and richened, and leaned out the mixture with no difference in the problem.

Any pointers?

BTW- recent replacements include fuel filter, cap, plugs, and wires. The rotor he got was wrong, but the old one looked good. Could a rotor somehow cause issues like this???

Getting voltage to the CPR?

I had a 5000 turbo that was constantly wrecking boost hoses causing all sorts of leaks and issues like that.

Have you checked the intake plumbing after the turbo?

vacuum leak?

Speedy:)

Check for vac leaks. Verify that the system fuel pressure is within spec both cold and hot. Make sure the warm-up (control pressure) regulator is functioning properly and is getting voltage. Also check to see if the cold start valve is turning off (sometimes they stick and get you rich mixture). If this is a model with O2 sensors make sure the O2 sensor is functioning properly (I think early Audi ECU's ignored the O2 sensor during warm-up and just ran open-loop).

Save yourself alot of grief and push it off a cliff.

angela (not an Audi 5000 fan)

We checked for vacuum leaks and found none. The CPR has power. The car is boosting at 1.4 bar in 3rd gear at WOT.

Has anybody heard of a faulty fuel pump relay causing issues on these? Apparently some Volvos with Kjet have had running issues with an old relay.

The timing also has us confused. We set the static timing to spec, but once the car is warm, the timing at idle is to far retarded. Turning the distributor did not affect timing. (Is this the knock sensor?)

This video is the car just started up after sitting about 10 mins after it was shut off at operating temp. The cars runs fine...

Audi running well - YouTube

Here is the car after 2 mins of running.

Audi not running well - YouTube

How did it run before changing the cap, plugs and wires? How long has this car been sitting / stored? You mentioned the rotor being wrong. Assuming the original was re-installed, is the end clean and is it properly seated on the dist. shaft, no cracks? I suggest to check the quality of the new plug wires too. Lots of junk aftermarket out there. Use Bosch Platnium plugs in that car.

I suggest to put all back to stock settings. But probably by now you have the CO off. As others mentioned, most problems stem from vac leaks. You'll still be able to pull that boost but need to seek out leaks. Some of those lines and special molded elbows usually are cracked at this age and not easy to see leaks. The heat cycles and heat rise on a turbo motor decay lines especially on top and the intake boot. While running, spray some carb cleaner around the rubber hoses, elbows, clamps near possible leaks and see if the idle increases. If I recall, the Idle Control valve was a common nusance but doubtful an issue with yours.

My Audi 5000 knowledge is very rusty, but I thought ignition timing on the '87 was driven by the ECU (not necessarily mechanical or vacuum advance). I think a failed knock sensor will force full ignition retard. I don't see that being necessarily temp-dependent. I still recommend verifying O2 sensor function. Also check the "multi-function temp sensor" (this thing provides info for the dash temp gauge and the ECU, but uses separate circuits for each).

I think the fuel pump relay only drives the fuel pump on the 5000's.

^^^^
THIS!!

'Audi' is German for don't own off warrantee. My guess is that an Audi 5000 is long off warrantee.