SL/R129: 1997 Sl500 misfiring

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May 20, 2017 | 11:56 PM

alexkocs

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Joined: May 2017

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1997 SL500

1997 Sl500 misfiring

Help, My 1997 SL500 starts to misfire after about 1 min of startup. Check engine light is on. OBDii scanner says multiple cyl. misfires. Also specifies cyl. 2 & 8 misfiring. Took to dealer and after several hundred dollars of diagnosis they think it is the ECU but will not guarantee it. They have replaced plugs, ruled out the O2 sensors, ruled out the injectors and coils by switching them to other cyls. Keep getting cyl 2 & 8 miss firing. I can get a used ECU from ebay for my model, does anyone know if it needs to be programmed or is it a plug and play for my model year? If I plug it in and start the engine will it cause any damage?
Completely baffled on this one!
Thanks
Alex

May 22, 2017 | 09:08 AM

bobterry99

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Joined: Jan 2006

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From: Atlanta, unfortunately

'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55

Quote:

Originally Posted by alexkocs

I can get a used ECU from ebay for my model, does anyone know if it needs to be programmed or is it a plug and play for my model year?

Mercedes considers the engine ECU to be an anti-theft component, and it is designed to work with just one vehicle. If you buy a used ECU for your vehicle it will not work without some sort of programming or electronic modification.

Someone may have managed to hack the ECU software and figured a way to program it to work with another VIN and now offer this service for sale. It is also possible to transplant one or more chips from your existing ECU to another.

Jun 4, 2017 | 08:07 PM