Hi Strick9 and welcome aboard.
Honestly from the problems you are encountering and from the year of production of your car I'm lead to believe too that your wiring harness is disintegrating. Before replacing it you should open it and see if the wiring insulation is melting or turning into sand to confirm the harness is going bad.

Hope it helps.

Cheers.

EDIT: I forgot to tell you that from time to time wiring harnesses can be found on Ebay otherwise it's a dealer part and unfortunately it's expensive.

 

harness ebay

check the interesting ebay finds thread - there's a harness there for 689.00 Hope it's still there that would fix you right up

 

A quick glance at any of the wires going to one of the sensors atop the engine will reveal broken, powdery insulation; the brown ground wire in the middle of the engine V is usually affected.
Caliber Motors (Mercedes Benz of Anaheim) sold me the OEM Mercedes replacement part (129-540-77-05) for $565 in June 2007.
Took less than an hour to replace.

 

thank you for the quick replies, I'll verify tonight if the wiring is falling apart(which I'm pretty sure it is) then get if fixed up as quick as I can. This foot of snow we just got will be melted soon and it will be soon time to have a bit of fun with it.

 

Fellow Calgarian and SL owner here. Might be a few more weeks before the snow and ice melts enough to take it out for a spring ride.

As I mentioned in another, similar post:
"I had to replace the wiring harness (and some damaged control units...ouch $$$$) in my '94 SL500. From my experience, I'd recommend replacing the harness on any '94 SL as a preventative measure rather than risk damaging other expensive electronic components".
Sounds like your having similar symptoms to what I experienced and are doing what I should have done before toasting very expensive control units.

Good luck!

 

My car has an erratic idle and lots of vibration. It also doesnt want to accelerate bearly has enough power to get up the drivewayl. Changed the distributor and rotors, has fuel has spark.. I'm wondering if it could be the wiring harness.. I'm in Calgary as well. I need this car working soon!

 

Hi Vicky Vallencourt and welcome aboard. It's important you fill your profile with your car and year and your location to help us help you in the best and quickest possible way.

Cheers.

 

check out item 360143534025 on ebay

Hi..I just noticed this listing on ebay, the bidding is at 75.00 for a harness. I don't know if that will help.
Take Care;
Dennis

 

Wrong part # for a R129

 

93 sl500 won't stay running and bad harness

Hi, I am an aircraft mechanic who owns a 93 sl500 that would run when cold, die when hot, occasionally backfire and had some check engine lights.
It now runs perfect! Here were the problems; First check the distributor rotors and caps and probably replace them. When you are changing them make sure the adaptor to the cam for the rotor is tight! Mine on my left side was loose, I ordered a new one and put it on, end of backfire and miss. The rotor and caps fixed my hard/hot start problem! I also put on new plug wires and new plugs for good measure. I replaced the crank position sensor for good measure also, it is on the top of the transmission bell housing. You can get to it easily from the top, it is under a plastic cover. I can assure you the engine wire harness is or will be bad! Mine was not causing the hard running but it was causing engine faults and a check engine light. Easy job to replace it and only about $600. I am going to replace the lower harness as my oil pressure gage failed. I found the wiring disintegrating so I repaired the wires to the sensor and now it works. Might as well put a new harness on and do it right. You can read all the codes and reset the check engine light and codes yourself.

 

Hi, I am an aircraft mechanic who owns a 93 sl500 that would run when cold, die when hot, occasionally backfire and had some check engine lights.
It now runs perfect! Here were the problems; First check the distributor rotors and caps and probably replace them. When you are changing them make sure the adaptor to the cam for the rotor is tight! Mine on my left side was loose, I ordered a new one and put it on, end of backfire and miss. The rotor and caps fixed my hard/hot start problem! I also put on new plug wires and new plugs for good measure. I replaced the crank position sensor for good measure also, it is on the top of the transmission bell housing. You can get to it easily from the top, it is under a plastic cover. I can assure you the engine wire harness is or will be bad! Mine was not causing the hard running but it was causing engine faults and a check engine light. Easy job to replace it and only about $600. I am going to replace the lower harness as my oil pressure gage failed. I found the wiring disintegrating so I repaired the wires to the sensor and now it works. Might as well put a new harness on and do it right. You can read all the codes and reset the check engine light and codes yourself.

I replaced the MAF, throttle actuator , distributer caps and rotors( i will check tomorrow to see if they are tight), wiring harness; this car is getting tiresome! and i have only until the 10th to get it inspected. still the same problem, starts , revs to about 1500 then in five seconds falls to 500 RPM missfires and almost stalls , sometimes does... absolutely no power! turning the wheels will make it stall, cant get it up the driveway.. Oh and theres a strong gas smell, it almost doesnt smell like gas.

Thx for the reply, Veronica.....