1995 SL500 Running Lumpy

[DanSL]

My car has been running lumpy when stationary or at crawling speed once warmed up - can anybody advise what the likely culprit is?

Thanks,

Dan

 

[bing]

Check your ignition parts, caps/rotors/seals/leads/plugs! When were they last changed?

 

[Pendragon]

Get a diagnostics done on it or you may find you are spending lots of money on parts you don't need. It could be a whole host of things and although we can all suggest what it could be, none of us can say for sure exactly what the problem is. I spent over £600.00 on parts and it eased the problem but didn't solve it.

Keith

 

[Doodle]

Finger pointing at usual suspects, much as per bing's post. Thankfully most of it is ascertainable by visual checks

First stop dizzie caps and rotors - if they're green and crusty, or signs of tracking it's time to change.
When were the plugs last changed?
I would suspect the car is still on original leads, in which case they're probably pretty crunchy by now and need replacing.
Take a look at the loom on the engine to see if the wiring is breaking down.

 

[bing]

Get a diagnostics done on it or you may find you are spending lots of money on parts you don't need. It could be a whole host of things and although we can all suggest what it could be, none of us can say for sure exactly what the problem is. I spent over £600.00 on parts and it eased the problem but didn't solve it.

Keith

Yes if you can plug it while it's happening. Otherwise, it's trial and error I'm afraid. Trouble is some skip on ignition maintenance coz they're spendy (bar plugs), then you're chasing this problem. M119s (pre coil overs) are prone to lumpy/miss/hiccup/stumble ..PITA !

.
Take a look at the loom on the engine to see if the wiring is breaking down.

Again spendy but a must !

 

[DanSL]

Cheers all - will be investigating soon. Went for a drive today and the problem was barely evident?!

 

[DanSL]

If I end up changing the rotors I remember reading somewhere that it's advisable to upgrade from MB to Bosch - can anybody confirm this?

 

[Doodle]

I normally go with Bosch or Beru from ECP.

MB original parts are becoming stupidly priced now, especially for something that on the 119 is almost a consumable item. I had a quote earlier this year for well over £300 for a pair of dizzies and rotors.

 

[DanSL]

I normally go with Bosch or Beru from ECP.

MB original parts are becoming stupidly priced now, especially for something that on the 119 is almost a consumable item. I had a quote earlier this year for well over £300 for a pair of dizzies and rotors.

Thanks; may I ask what you paid last time you had the job done please?

 

[bing]

Cheers all - will be investigating soon. Went for a drive today and the problem was barely evident?!

Normal, but will come back! (Sorry to say) You need to investigate/check when the rest of ignition parts were replaced. Ideally you should change caps and rotors at the same time at the very least! Also, 1 item that's overlooked is the insulator where the rotor sits : http://www.w124performance.com/docs/mb/M119/ignition_misfiring_STAR.pdf

part#MA119 158 01 88 it comes with a rubber seal. Not cheap at £78+VAT last I bought a set AFAIK you can only get these at the Dealers. Now you see why some would skimp on some of these bits, and remember you need 2 of each - bloody rip-off !

If I end up changing the rotors I remember reading somewhere that it's advisable to upgrade from MB to Bosch - can anybody confirm this?

MB use Bosch caps and rotors so you're fine .

 

[Doodle]

Bad news there. The insulators are NLA from Mercedes, I asked a few months back. Might be able to get something from Bosch, part# is 1-230-500-240 IIRC. However, I do question the "severity" of that article - mine look fine after 18 years and 130k, and this problem only ever seems to appear on the American forums?

Dan, I change them myself, takes a few mins with basic tools. Beru are 160ish from ECP with forum discount, Bosch probably closer to 200, so you can see there's a fair saving over MB original parts.

 

[jaymanek]

The insulator plate was gone on my 300TE 24V M104 engine causing a lumpy idle but never has issues on any M119 with those...

Bosch parts are the best,,, MB are just far too expensive for the rotors and caps.