R129 M119 engine - rough idle

[JuBe]

I drive R129 1994 SL500, but I have a problem with rumbling or bad idle of the engine, I checked for any false air getting in, changed the rubber seal on the throttle body and the engine (it was broken) I was 100% sure it would solve the problem..but nothing! I also gave injectors cleaning, and spark plugs are original and in good condition IDK what else to check. can you please give me a few tips? my next plan is to check the pressure in the injectors "tube"

 

[star]

Check the valve timing, we have seen the chain wear and the os cam timing be so far out it causes misfires.

 

[JuBe]

Can you please be more specific? More info
Sorry, im new to mechanics

 

[LostKiwi]

Does yours have distributors or is it the coilpack version?

 

[JuBe]

Distributor cap, but i know for this problem..i took it off and whiped it, its also in new condition

 

[mimile]

The distributors caps are the usual trouble on this engine, some french SL500 owners have to change them every two years...

 

[LostKiwi]

In that case start with verifying you don't have a disintegrating wiring loom. These cars of that age are known for it. Then double check for vacuum leaks especially around the back of the manifold where there are a few take off points. Also check breather hoses as these can go brittle with age and crack.
Ideally try to look at live data from the lambdas and the MAF if possible to make sure they're doing as expected (don't even think about changing the MAF just to see if it fixes it as they cost a fortune).
Then change caps, rotors and leads. These cars are very hard on ignition components and even if it doesn't fix it it good to have a spare set as you will need them for sure at some point.

 

[JuBe]

Thank you very much on detailed answear, i had a bussy week, through out this one im getting new tires and im gonna be looking at all the vacuum lines, on some youtube video someone mentioned switchover valve, il check that, il come back here with steps and pics, maybe if someone else runs into a problem like me.

 

[Richard Moakes]

Check the valve timing, we have seen the chain wear and the os cam timing be so far out it causes misfires.

Is that a cam covers off job, and check timing marks?


Sent from my iPad using Tapatalk

 

[star]

Unfortunately yes.

 

[gassed up]

I'm with LK on this one, the under bonnet wiring harness is a bio-degradable nightmare.

 

[LostKiwi]

I'm with LK on this one, the under bonnet wiring harness is a bio-degradable nightmare.

Indeed....

 

[gassed up]

you and me both