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Old 06-11-2002, 09:55 PM
hbofinger hbofinger is offline
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Join Date: May 2002
Location: Washington, D.C.
Posts: 398
Unhappy 560 SEL Rough Idle (Another one!)

OK. I really need help now. I don't want to take this thing into the shop to have this diagnosed, but I still have a rough idle problem on my 560 SEL. It's rougher when cold, and gets better when warm, but still feels like a cylinder is "missing" occasionally, even though no bad cylinder can be isoloated by pulling the plug wires.

So here are the exact symptoms:

Oil pressure gauge fluctuates with the roughness, though the change in RPM is not sensitive enough to be seen in the tachometer. The roughness feels like the engine is being hit with something occasionally.

It seems the engine is reving and slowing down in 5-second cycles, though it is too subtle to see on the tachometer. It can be heard, though, when under the hood.

It's driving me nuts!

Here are some background facts:

1. Vacuum is great - tested it with a gauge, and visually examined everything.

2. New injectors, seals, seats, etc.

3. New fuel filter

4. All secondary ignition parts new (wires, plugs, coil, cap, rotor)

5. Air filters new.

6. OVP valve new

7. Fuel pump relay new ('2000)

8. One of the fuel pumps looks new.

9. 98 k miles

10. All parts OEM.

Any way I can diagnose this without going to the dealer?

Thanks for any help....
Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)
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