SL/R129: advice needed
Thread Starter
Newbie
Joined: Apr 2010
Posts: 13
Likes: 0
1992 300sl-24
advice needed
How you guys doing.Im not too good.My 92 300 sl is not doing well.The car
idles rough and it seems to have a lot less power on the highway sometime I cant get above 55 on the 95 in Nevada,I replaced the wires 6 months ago and i replaced the coil and dist cap yesterday but it made no difference.The no 5 spark plug seemed wet with gas I assume.So I replaced it and it seemed to make a difference for a short time but it started all over again.It seems to run worse the longer i drive it.I cant really afford to go to the dealer.And I dont know any honest and reasonable shops in the Henderson Nv area.It is my daily driver.Thanks for any guidance.Peter
idles rough and it seems to have a lot less power on the highway sometime I cant get above 55 on the 95 in Nevada,I replaced the wires 6 months ago and i replaced the coil and dist cap yesterday but it made no difference.The no 5 spark plug seemed wet with gas I assume.So I replaced it and it seemed to make a difference for a short time but it started all over again.It seems to run worse the longer i drive it.I cant really afford to go to the dealer.And I dont know any honest and reasonable shops in the Henderson Nv area.It is my daily driver.Thanks for any guidance.Peter
Super Member
Joined: Jul 2010
Posts: 598
Likes: 19
From: Eastern Kansas
94 SL 600, 98 993, 89 XJS Conv., 85 Daimlier Princess 16 Hybrid Lincoln 16 Chevy crewcab
Sorry you can't run with the fast dogs, the vehicle, without issues certainly can perform with the best of the 92 model year!
The way you describe the speed and sluggishness makes we think of the LHM (limp home mode ) that can be from many problems. The car has a diagnostic process that ( for me ) required an INDY with experience. The cost was major by the time all the issues were sorted, but without I would have replaced lots of expensive parts with only blind luck producing any change. The R129 is a long way from the 59 VW bug I could restore to function with pliers, screw driver and high heat duct tape.
Once you have the diagnosis of the problems, then DIY with the needed parts can bring you daily drive back to you!
The way you describe the speed and sluggishness makes we think of the LHM (limp home mode ) that can be from many problems. The car has a diagnostic process that ( for me ) required an INDY with experience. The cost was major by the time all the issues were sorted, but without I would have replaced lots of expensive parts with only blind luck producing any change. The R129 is a long way from the 59 VW bug I could restore to function with pliers, screw driver and high heat duct tape.
Once you have the diagnosis of the problems, then DIY with the needed parts can bring you daily drive back to you!
Last edited by SRHsl600; Nov 22, 2013 at 03:03 PM. Reason: spelling
Newbie
Joined: Jun 2008
Posts: 9
Likes: 0
1998 SL500 R129
running rough
try maff sensor, leads and maybe crank sensor. If you find it is sensor some good advice is only take the Bosch route, there are lots of cheapies on ebay but you get what you pay for. OEM is only way to go for that. It is easy diy job to take off and check/clean and to replace.
MBWorld Fanatic!
Joined: Jul 2012
Posts: 1,556
Likes: 15
From: Canada
07 E63 + 07 CLK63CAB
Just for your peace of mind pull #5 again and check it for wetness, are the plugs fresh. Is the compression good in all cylinders. If the plug is black , maybe oil which could call for a hotter range plug in that #5 cyl. Keep us posted with results, Good Luck
Thread Starter
Newbie
Joined: Apr 2010
Posts: 13
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1992 300sl-24
Thanks for the advice I really appreciate it.turns out the valves from cylinders 3 and 5 were almost completely burnt out so i assume that is my problem.In the other 4 cylinders the valves were in almost perfect condition.Cant figure that on out.Thanks again for your help
