Sever Power Loss 500 Sl - PeachParts Mercedes-Benz Forum

MAGV5 · #1 04-28-2008, 10:00 AM

1986 500 sl

SEVER POWER LOSS. Will not run over 50 MPH and has no acceleration at all, just bog down. Dones not hesitate on initial acceleration. Reaches about 15 mph in first gear and engine bogs down, back off the accelerator and the xmsn will shift into second and the process starts all over again.

Things I have checked: Ignition timing +5 at idle +10 with vacuum adv connected. EZL has been replaced with on known to be good. O2 sensor checks OK. Fuel pressure 85-90 lbs on road test. Cold start injector activated during engine bog (for extra fuel) but made no difference. Engine runs Hot 100 +, but never to the redline. Oil pressure normal and engine does not smoke or knock.

Advice / suggestions welcome

MAGV5

ScottinSoCal · #2 04-28-2008, 10:57 AM

Quote:

Originally Posted by MAGV5

SEVER POWER LOSS. Will not run over 50 MPH and has no acceleration at all, just bog down. Dones not hesitate on initial acceleration. Reaches about 15 mph in first gear and engine bogs down, back off the accelerator and the xmsn will shift into second and the process starts all over again.

What you're describing is the classic symptoms of a clogged catalytic converter. If your car isn't equipped with one I'd look for some other kind of severe restriction in the exhaust system, like a collapsed muffler (although you'd probably hear that at any speed).

ctaylor738 · #3 04-30-2008, 06:08 AM

Where in the system did you measure 85-90 psi fuel pressure? That's high for system pressure, and off the chart for control pressure. What do the spark plugs look like?

tecqboy · #4 04-30-2008, 11:41 AM

Does this car have an OVP relay / fuse?

edsl94 · #5 06-24-2008, 09:05 PM

sounds like the exhaust. i had a dodge van do that. a new cat and muffler put me back in good shape.

combat customs · #6 07-02-2008, 01:55 PM

I don't know if your 500 has an ASR switch on it or not, but your problem mirros one that I had on my SL600. At the back of the engine on both side of mine are an ASR box that has an electronic and gear stes in them. They will not let you accellerate at any speed if shorted or broken. The local Benz dealer here wanted $4,600.00 to replace it. Through their tests it was isolated to the driver side box. When I took it off and took it apart it was full of the plastic wire coatings for the electronic parts. I don't know if it was overheated or just due to age. I seperated all the wirres coated them with liquid plastic replaced it and it has run perfect for over 3,000 miles now. Cost me .50cents worth of liquid plastic. Might be your curre.