My new (5000km) spark plugs all look burned out (1997 R129)

[Benzy Boy]

Moderator edit: Updated thread title to include year/model of vehicle, which has a different ignition system than the 400E/500E.

All 8
Engine is 120,000km
No other issues except vibration felt in seat during idle.

 

[gsxr]

The discoloration on the bottom of the insulator is either oil contamination (unlikely, since it's dry otherwise) or rubber residue from the plug boot.

The important part is the tips, and although they aren't clearly visible in your photo, they appear fine.

 

[Benzy Boy]

Thanks for the perfect answer as always gsxr. But whoops I replaced them all anyway before I read this post. I still vibrate on idle! Darn it....

 

[maw1124]

Seems like you’ve been chasing a lumpy idle issue since you got the car. Is that correct?

If so, given that you’ve changed mounts and plugs, have you looked at distributor caps and rotors? I want to say Yes, but my memory could be off. If not, go there next.

If yes, how does she act under load? If fine, I’d check fuel filter next.

If poor under load, then you want to think about fuel pumps but check back here first. Injectors tend not to be problematic on these but at this age I suppose anything could happen.

GL

maw

 

[Benzy Boy]

Seems like you’ve been chasing a lumpy idle issue since you got the car. Is that correct?

If so, given that you’ve changed mounts and plugs, have you looked at distributor caps and rotors? I want to say Yes, but my memory could be off. If not, go there next.

If yes, how does she act under load? If fine, I’d check fuel filter next.

If poor under load, then you want to think about fuel pumps but check back here first. Injectors tend not to be problematic on these but at this age I suppose anything could happen.

GL

maw

What am I looking for on distributor caps? Moisture? How do I diagnose them?
Fuel filter was changed last year (5000km) and using top tier fuel.
Under load is fine. Vibrations come in as a deep oscillating rumble in my seat and door.
I have experience with a bad exhaust hanger that caused the pipes to hit against the chassis and that vibration was totally difference than this.
This feels like it's 100% from the operation of the engine or transmission and it's a lot more like a slow rumble or extremely soft constant shudder that you can feel in your seat.

 

[maw1124]

Yes moisture. Full disclosure, mine were diagnosed and changed when I didn’t even recognize it. I can’t think of anything else TBH.

GL

maw

 

[TerryA]

View attachment 174470

All 8
Engine is 120,000km
No other issues except vibration felt in seat during idle.

The plug tips look good as new to me. Looks like some kind of burnt oil on threads and ceramic insulators. Is oil leaking down into the plug holes from the valve cover?

 

[Benzy Boy]

I’m 1997 I don’t have distributor caps so it can’t be that.

OBD reader showed no codes.

Must be transmission mount that gave up. It was Lemforder made in India, what’s the verdict on those?

 

[Benzy Boy]

The plug tips look good as new to me. Looks like some kind of burnt oil on threads and ceramic insulators. Is oil leaking down into the plug holes from the valve cover?

Yeah I saw some dried up oil there. But how did it get there?

 

[TerryA]

Yeah I saw some dried up oil there. But how did it get there?

Probably from the 8X rubber gaskets that seal the spark plugs from the valve cover oil.

 

[nocfn]

If you have that idle problem, you really need to replace the cam seals, the insulator, the rotor (change bolt size) Bracket, cap, accent the slots on the cap out of the box, wires and finally the coils. That is to say, if these things are OE or no records of it being changed. I will also say if the cam magnets are leaking around the plugs and they are oily just bite the bullet and replace them. since all that crap is off, *and you will need to remove reservoir to PS, you should do all that hose work too. You will be fresh, the electrical system is now replaced and baseline from which all things come from. (rubber bits in the engine bay are fossilized, so that should all be replaced right down to the vac line connections. get it all done, reset the adaptation and you will be a happy driver. Hate to spend your money but this work should be done and there is absolutely no reason to head bang for months and get pissed and quit. Make a plan, take the time to acquire what you need and get it done. (valve cover seals, oil separator, metal cam oilers, upper chain guides potentially rail, chain stretch are additional while you are in there items)

 

[maw1124]

I lost the thread when he said 1997, which means he’s not talking about a .036. I’m not sure we’re diagnosing the right car.

maw

 

[gerryvz]

I lost the thread when he said 1997, which means he’s not talking about a .036. I’m not sure we’re diagnosing the right car.

maw

And that is why the thread was moved to "Off-Topic Discussions," as it does not relate to the LH injected M119 that is the heart of the cars that this forum primarily deals with.

A note to @Benzy Boy -- this forum primarily deals with the W124 chassis cars with M119 engine that employs LH injection. While we are friendly to related cars and models, and engines (such as the M104, or ME / CIS-E injected versions of the M119), any and all posts specifically dealing with non-W124 and non-LH-M119 and non-722.3 transmission related topics MUST be posted to "Off Topic Discussions" sub-forum, NOT to the forum's main engine and transmission forums.

This ensures that topics discussed in the main forums are specific to the W124/LH-M119/722.3, which are found in the 400E, 500E, and a few related models such as the R129 SLs.