1995 SL500 Performance Woes Again

[tmwsccsh]

All,

Further to my posting at the start of the year with regards to performance issues, alas, this morning I have another one. Not sure if it's related to the previous but here goes.

I haven't used her for about 3 weeks so thought I would take her in to work today - about 6 miles. Stopped off about half a mile from the office to get a bottle of water. Now, I noticed that once she had warmed up and got to about 80 degrees or so that the idle started hunting a bit - similar to the problems I was seeing with the MAF earlier this year.

Got back in the car after purchasing and started her up - idle was rough and going up and down a bit. Put it into R to pull out and it died - completely. Back into P and started her up again. Idle was going between about 300 and 800. Back into R and it cut out. This was repeated about 6 times before I managed to actually pull out of the space, but there was no power at all unless the revs got to over about 1700.

I decided to take her back home at this point and swap back to the daily. All was fine driving along, however as I stopped at roundabouts and traffic lights, the revs were again all over the shop and there was no power or take off until about 1700 RPM when it kicked in - almost stalled out about 3 times. In the end I had to drive with the left foot on the brake at lights to make sure I could pull off.

Now as another side-note, all was fine until she got up to temperature (around 80 degrees). Interestingly, as advised in a different posting earlier this year, the Oil light now comes on when she goes above 80 degrees - not sure if this is a symptom or clue or not. The temperature did also continue to climb a bit up to 100 whilst stationary but moving brought this back down again - I would not have expected this on a short, 12 minute journey.

So, anyone got any ideas what could be going on and where I can start on this one?

I would drop it in to be looked at but after last time I had similar issues and the car was there for 3 months I am hesitant and would consider going elsewhere but not sure where at this time.

Thanks in advance for any guidance.

Regards

TMW

 

[Doodle]

When did you last have a look at the state of the dizzy cap and rotor?

 

[Sp!ke]

This sounds very much like typical condensation issues in the distributor caps after you stopped the car.

 

[tmwsccsh]

This sounds very much like typical condensation issues in the distributor caps after you stopped the car.

Hmm.

What's the best way to check them?

And is there a way to stop it happening?

It is interesting that it started getting rough once it reached temperature though - can't believe it was condensation at that point?

TMW

 

[tmwsccsh]

When did you last have a look at the state of the dizzy cap and rotor?

They were replaced about 4000 miles ago.

TMW

 

[BlackC55]

If you don't use the car much they are almost an annual replacement.

 

[Doodle]

They were replaced about 4000 miles ago.

TMW

If you're not using it often that could be many months though? I usually give mine a quick check every couple of months.

Hmm.

What's the best way to check them?

And is there a way to stop it happening?

It is interesting that it started getting rough once it reached temperature though - can't believe it was condensation at that point?

TMW

Pop them off and clean them. With practice it takes a few minutes.

Not really. Keep them clean, make sure the insulator plates behind the rotor fit well.

Up until that point, the car will be on fast idle which masks the symptoms.

 

[tmwsccsh]

Am I right in thinking it's behind these plastic parts I need to be looking?



TMW

 

[bing]

correct !

 

[Doodle]

That's it. Take the front part of the air cleaner off (the louvred section), and the hoover tubes. Pop the covers off, you'll need a 5 or 6 mm one for the cap, and a 3-4mm one if you want to remove the rotor arms (I can't remember the exact sizes, I have 2 stashed in the car for this purpose).

 

[Sp!ke]

H

It is interesting that it started getting rough once it reached temperature though - can't believe it was condensation at that point?

TMW

It is the heat of the engine that forms the condensation out of the damp air.

The only real long term solution to this would be to ensure a complete seal on the distributor caps. There should be a rubber seal on the base of your caps - does it look intact and serviceable and what caps do you have Bosch or Beru?

Have a quick read of this thread http://www.benzworld.org/forums/r129-sl-class/1638170-m119-distributor-caps-moisture.html

 

[tmwsccsh]

It is the heat of the engine that forms the condensation out of the damp air.

The only real long term solution to this would be to ensure a complete seal on the distributor caps. There should be a rubber seal on the base of your caps - does it look intact and serviceable?

Hence why it doesn't happen in the summer?

I seem to recall someone suggesting previously that you could drill a hole in the top of it and that would help - any thoughts on that?

TMW

 

[tmwsccsh]

Have a quick read of this thread M119 distributor caps.. moisture!! - Mercedes-Benz Forum

There's some good information in this - thanks for the link!

Alas, I am away this weekend, but I know what I am doing the one after...

Regards

TMW

 

[tmwsccsh]

Evening All,

Right, I have today taken the Distributor Caps off and had a look behind and, well, see below...

Back of Cap...


What is behind the Cap...


I see no moisture, or I am suppose to take something else out behind it as well? The 2x images shown are the left-hand side, but the right was no different (similar images of the right hand side are available if required).

I let her run up to temperature before taking the caps off and, before shutting off, the revs were all over the place as usual once she reached temperature.

After taking the Caps off, checking and replacing them again I started her once more and the same thing :-(

Now, one minor thing. I spotted the throttle cable (or what I assume is, as below) and did some revving - see below...



After wiggling that a few times, the revs didn't go back to the same natural position as they would using the actual accelerator pedal and were holding around 800rpm or so instead of the bouncing from 300 to 600 or so and stumbling - it was stable at 800 and if I then used the accelerator to give a push of power, it dropped back to 800 again and stayed there. Don't know if this is of interest or relavence but I thought it odd.

Turned her off and started her again and after about a minute the revs were bouncing.

Turned her off and started her again then moved the throttle cable as above and the revs stayed around 800 solid again.

Revs get more sporadic in R or D but this is understandable, although when using the throttle cable "trick" going to R and D did not have any bouncing issues. Although the ASR light did come on and would not go out until she was powered off and on again.

The MAF sensor was replaced in March that seemed to resolve it but as the garage had her for 3 months I do actually wonder if the MAF didn't actually need replacing and it was the arrival of the Spring season that actually fixed it, hiding another underlying issue...

I have to be honest, as this is exactly the same as what happened last year around this time I do wonder if it is weather related as there were no issues in the spring and summer months. However, if I can't get this sorted I am considering selling her as I can't go on like this each time I want to use her in the winter. I don't want it to come to that as when she works she is great but this is really getting to me and it's just not worth the hassle at times.

Does anything in here give anyone any pointers as to wherelse I can be going here to get this sorted?

Thanks in advance.

Fed up of Letchworth

 

[Doodle]

There's a lot of what looks like oil on the seal of the cap, and covering the rotor arm and insulator...that is not good. The cap also looks pretty grubby inside, and the grunge on the contacts that would benefit from being removed.

If I get a chance I'll get you a pic of mine for comparison tomorrow.

 

[tmwsccsh]

There's a lot of what looks like oil on the seal of the cap, and covering the rotor arm and insulator...that is not good. The cap also looks pretty grubby inside, and the grunge on the contacts that would benefit from being removed.

If I get a chance I'll get you a pic of mine for comparison tomorrow.

Thanks - that would be greatly appreciated.

For reference, here's the right-hand side one too...





The outer disk like thing behind - it spins round but I couldn't get it out - is there a trick?

And what's the best thing to clean it with?

Thanks in advance.

Oh, and thanks for the quick reply.

Regards

Tim Watts

 

[Doodle]

That's a bit better, not quite so covered in grunge. Contact cleaner on a clean rag will do.

To get the insulator discs out you have to undo the rotor arm, and then the carrier.

 

[tmwsccsh]

That's a bit better, not quite so covered in grunge. Contact cleaner on a clean rag will do.

To get the insulator discs out you have to undo the rotor arm, and then the carrier.

Cheers - Having looked at the photo again myself I can see the heads for the rotor arm - couldn't see them clearly enough in the car but at that angle it's obvious!

As a matter of interest, how do you get the leads off the Disty cap? I twisted and pulled and nothing budged - there's probably an obvious trick I missed...

Thanks.

TMW

 

[Sp!ke]

Look at all the crud on the contacts in both caps! I think they need a good going over with some emery board to clean them up in the fist instance as well as probably cleaning up the rotor arm itself. They don't look to me like they were changed that recently imho.

I would also be concerned with all the oil inside there. I would give everything a thorough clean and go for a drive and then open them up again and see if you can figure out where the oil is coming from and then replace whatever seal or gasket has failed. it looks like the orange seal under the distributors is misaligned or in need of replacement for starters. This needs a perfect seal with the cap in order to stop the condensation issues you are experiencing.

 

[bing]

Doodle and spike are correct on this .

Looks like you have oily residue rather than moisture on both sides which really should be addressed. Likely a seal on the cam radial shaft that may need replacing. Not an easy a job as I believe there's a special tool required to press the rubber seal in properly!

Quite common on M119.96/97 engines . Like so:

This probably what your insulators look like when you remove them

Seal and special tool :