560 SEL in "limp" mode...
 

Hi all, I just did a plenum seal job on my 1989 560 SEL. I had my mechanic go over the work, do a smoke test, all is solid and OK. He congratulated me on the job. But the car does not accelerate worth crap. It is beyond his knowledge, he suspects something electronic. The problem started after the transmission was replaced.

What would put a 560 SEL into "limp" mode? He noticed that the spark does not advance as you attempt to accelerate the engine.

Any pointers would be appreciated. There are no vacuum leaks, everthing is tight, and the mixture has been adjusted.

Timing on a 560SEL is done by the EZL which needs to have a vacuum hose connected to it

vacuum connects to number 1 on this picture:

https://www.benzworld.org/attachments/ezl-jpg.2343658/

you can check with a vacuum gauge if there is vacuum from the line


Also another tip: clean the inside posts of your distributor cap. You won't believe how dirty they can get I have to clean mine every month or two.

Thank you for your helpful reply, will follow up on the vacuum line.

Check all throttle linkages carefully. Something might've gotten thrown off when the transmission job was done.

Did the congratulatory "mechanic" also replace the transmission?
What is the chronological order of the intake work and the replacement of the trans?

First: Transmission exchange. Replaced it with a Sun Valley rebuild. Old one was smoking, no power issues.

Second: Power issues appeared. Mechanic blamed Plenum Seals. I did the job over a three month period. Seals were bad, also found a cracked hose under the fuel distributor.

Third: Upon starting, the power problems persisted.

Just did a vacuum test by the EZL: It is receiveing strong vacuum, so this is not the issue. Suspect bad EZL... (timing not advancing with increased rpm)

Linkages are ok... I do wonder about the crank angle sensor, except that a friend of mine has stated the engine would not even run if something were wrong there...

Vacuum OK!
 

Checked it with a gauge, there is vacuum...