R129 500SL misfire when engine warms up cured

[Ned]

Hi Guys

My 500SL has been hesitating and stalling when accelerating from idle only once the engine warms up. Its fine from cold and always starts back up once it stalls and the idle was a little lumpy.

In the past I have changed the plugs, rotor arms, distributor caps, leads, camshaft oil seals, vacuum hoses, etc with no improvement, even tried the silicone grease in the distributor caps to try and rule out condensation.

Today I changed both the coils and the problem is gone, the idle is a lot smoother now and the car pulls away smoothly all the way through the revs. Looks like they were breaking down once they heated up and the spark was intermittent.

I hope this helps those of you in a similar position, the M119 engine seems to have a very sensitive ignition system.

Ned

 

[John Laidlaw]

Thanks Ned!

 

[LostKiwi]

Interesting as mine the exact same issue!

 

[bembo449]

impreza turbos were a bugger for this , the coil plastic onto the plug fractures and causes a misfire but its hard to spot

 

[Ned]

Interesting as mine the exact same issue!

The symptoms seem to be common on the M119.

The coils tend to be overlooked because I assumed they either work or they don't.

Mine were the originals so can't complain they were failing after 27 years service. Replaced them with Bosch and all is good so maybe worth a go.

 

[roblloyd]

Hi Guys

My 500SL has been hesitating and stalling when accelerating from idle only once the engine warms up. Its fine from cold and always starts back up once it stalls and the idle was a little lumpy.

In the past I have changed the plugs, rotor arms, distributor caps, leads, camshaft oil seals, vacuum hoses, etc with no improvement, even tried the silicone grease in the distributor caps to try and rule out condensation.

Today I changed both the coils and the problem is gone, the idle is a lot smoother now and the car pulls away smoothly all the way through the revs. Looks like they were breaking down once they heated up and the spark was intermittent.

I hope this helps those of you in a similar position, the M119 engine seems to have a very sensitive ignition system.

Ned

Great to kno ned, might be my answer once i find out how to fix my driver window not working. Getting roadster soft top error code 10-17. If you get the time can you have a look at the code and see if you understand the problem.
Thanks
Rob

 

[DREAMER NO2]

Ned the old 12 volt coils were the same , when they get hot they would short out ..