93 500 SL, engine running rough - Mercedes-Benz Forum

 
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post #1 of 2 (permalink) Old 06-19-2010, 08:14 PM Thread Starter
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Date registered: May 2010
Vehicle: 1993 500 SL
Location: Cabot, Arkansas
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93 500 SL, engine running rough

I recently bought a 93 500 SL. It is show room new looking. All original paint and interior. I'm not kidding, it looks like I just drove it off the floor.

But, it has a rough running problem. When I bought it I thought it probably just needed plugs and wires. The price was right. I figured it wouldn't take much to straighten it out. Boy was I wrong. When I was trying to figure out the problem I saw a bare wire to the right cam sensor. When I started to fix it, all the insulation on all the wires just crumbled. I had to totally re-wired all the engine wiring. I put new plugs and wires on. Nothing changed, it still idles real rough and hesitates. Seems to run good once to get past the surge. Next I put a new MAP sensor on. Still no change. It runs exactly the same as it did the day I bought it. So nothing I did made it better or worse. I did notice that the MPG gauge goes to 0 even at idle. I'm pretty sure that's a vacuum operated gauge, maybe not. I just thought it might be related somehow.

I have no way of reading the computer and wouldn't know what I read if I could.

Anyway, I would really appreciate some help.

I really would hate to have to take it to the dealer. No telling what that would cost and they would try to blame my wiring. I've been building cars and engines for 40 years, but this is my first and maybe last Mercedes.

Take care, Larry
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post #2 of 2 (permalink) Old 06-19-2010, 10:08 PM
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Date registered: Jan 2007
Vehicle: 1962 W111 220SE Coupe
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Quote:
Originally Posted by Earthloc View Post
I recently bought a 93 500 SL. It is show room new looking. All original paint and interior. I'm not kidding, it looks like I just drove it off the floor.

But, it has a rough running problem. When I bought it I thought it probably just needed plugs and wires. The price was right. I figured it wouldn't take much to straighten it out. Boy was I wrong. When I was trying to figure out the problem I saw a bare wire to the right cam sensor. When I started to fix it, all the insulation on all the wires just crumbled. I had to totally re-wired all the engine wiring. I put new plugs and wires on. Nothing changed, it still idles real rough and hesitates. Seems to run good once to get past the surge. Next I put a new MAP sensor on. Still no change. It runs exactly the same as it did the day I bought it. So nothing I did made it better or worse. I did notice that the MPG gauge goes to 0 even at idle. I'm pretty sure that's a vacuum operated gauge, maybe not. I just thought it might be related somehow.

I have no way of reading the computer and wouldn't know what I read if I could.

Anyway, I would really appreciate some help.

I really would hate to have to take it to the dealer. No telling what that would cost and they would try to blame my wiring. I've been building cars and engines for 40 years, but this is my first and maybe last Mercedes.

Take care, Larry
MB used a biodegradable wiring harness during this time (until 95 or 97 I believe) and the crumbling insulation is a clear symptom. Repost this is the R129 forum listed under roadsters from the main menu and the folks there who own the same car will be able to provide some useful answers. Good luck!

-Marrs

The Coupe Group (W111/112 coupes and cabs)official website
The Coupe Group on Facebook


"Too many people are working at jobs they hate, to buy things they don't particularly want, to impress people they don't even care about." --Dr. Deepak Chopra
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