Hi,

I got a 1989 560SEL that is rough on warm start after standing for 10 minutes or so. Cold start is fine. The start itself is fine, it just that the engine vibrates as if not running on all eight. Some addition background:

• Accumulator - New
• Fuel flow check valves at pumps - New
• EHA - new
• Injectors & holders & seals - did those about 10 years ago
• Fuel filter - new
• Idle after cold start - perfect! Smooooooth.....
• idle after a minute or so after warm start - perferct! Smoooooth!

However, even if I press the gas pedal after a warm start the engine vibrates as it picks up rpm. The overall vibration settles down after a minute or so.

A good friend of mine suspects the injector seals. Any other ideas?

Mileage 128k (Love the car!)

__________________
Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)

Leaking fuel injectors.


Sent from my iPad using Tapatalk HD

The seals? The injectors themselves only have about 30,000 k on them, I replaced them 10 years ago..

__________________
Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)

Post warm-start with KE the system is in open loop, the mixture is strongly influenced by the water temperature signal, and shifted in the lean direction. Shortly after start the O2 sensor signal becomes valid, the system goes into closed loop, the EHA becomes active, and the mixture is enriched.

Try setting the basic mixture 1/8-1/4 turn richer (CW).