Merc Misbehaving Malarky

[dollywobbler]

I bet a fairly large amount of Curly Wurlys that's your problem

 

Oh, forgot this. When can you deliver?

[dollywobbler]

Further investigations this evening focused on the OVP relay. I managed to find it, prise it out of its aluminium case and resolder the joints. This has made no difference at all so either my resoldering was not up to much, or the OVP isn't at fault. I wish I had another to try so I could properly eliminate it.

 

However, it was misfiring even when the coolant was still cold, so that's something! Garage reckoned the plugs were white, suggesting it's too lean. Yet the smell is too rich. Confusing.

[Albert Ross]

It is all pointing to an air leak at the inlet manifold, suggesting a breather or vac control hose or pipe split, or a perished elbow. The reason the engine sounds and smells rich, is because it is sensing the excess oxygen, and running fast, so it enriches the fuel to make it smoother. Remove each vac hose off the manifold in turn, whilst the engine is running, and if it makes a difference to the idle speed, that's not it. It it makes NO difference, stick your finger over the pipe, if it smooths out the idle, then trace it back to source, checking each joint as you go. (Finger over the end) DId you try to find the Cruise control vac circuit? The thingy behind the headlamp I suggested....!

[RichL]

I love these old Merc's. Well built with classy, handsome understated style which we will never see again, sadly. VO reg number means it started life around here (Notts).

Good luck with getting it sorted, will hopefully be something simple and cheap. Before you know it will be puuring like..err..a kitten...

 

 

Oh and the vRS. I have driven one and I love them, loads of power in any gear, at any time and any revs. They handle pretty good as well.

[dollywobbler]

To be honest, there are so many hoses and pipes all over the place that I've got no hope of tracing it all. The intake manifold is entirely hidden by the air filter. I can't see any issues with the various bits of piping I have found.

 

Bol's theory might hold water, or the oxygen sensor itself could be up the duff. It's proving what's at fault that's going to be tricky.

 

However, having run the engine in the dark, it doesn't appear that the plug leads are an issue, though I will be looking to replace them at some point anyway. No arcing.

[Rocket88]

See if you can find a garage with a smoke machine......quickest way of finding air leaks.PM me your address for Curly Wurly despatch!

[Tetleysmooth]

If it's got tits or tyres, it'll cost ya!!

 

Just my way of comforting.......

[Barry Cade]

I think you're all getting a bit too modern minded here... it's a G reg, so 1989. Won't have a Cat or oxygen sensor unless someone specced the hugely expensive and very rare G Kat option when new... Bosch K Jetronic is purely a mechanical system, so coolant temp operates bimetallic strips rather than fancy electronics. The mixture is adjusted with a long allen key (3mm) through a hole in the air filter. Start with the old car basics, plugs, leads, mixture settings etc... and waft a bit of plus gas or similar round the inlet manifold to see if there are any vaccum leaks. K Jet is also very dependent on fuel pressure, is the pump noisy? Fuel filter look recent?

[dollywobbler]

Not had much time for tinkering today, as I went to see a friend so we could improve the BX. This we did. Gratification delivered by France. Germany still in the sin-bin.

 

I did find a broken vacuum pipe. That's been repaired. A very slight difference. No idea when the fuel filter was last replaced, but it's behaving as if it's too rich rather than too weak. A proper service is on the to-do list, but I've got to get it running better before the MOT. I am going to have a tinker with the mixture tomorrow - it's pretty easy to do it in a measured way so you can revert back to previous settings.

[dollywobbler]

Progress. I weakened the idle mixture today and it now picks up much more promptly. There's still a misfire, but it seems more consistent so hoping new plugs and leads (the leads really are pretty dreadful) will cure that. The car is much more driveable - it no longer bogs down completely.

 

What is an annoyance is that I've had to order a special pair of pliers just to remove the plug leads. What a stupid design. I did pull one plug out after doing battle with the lead. It just looked well used. The gap was a bit too large - I think these are fussy about that - so for the first time in my life, I'm going to have to gap a set of plugs before fitting them. I'm not used to owning such a fussy car!

[dollywobbler]

Mmmmmmercedes.

 

It's nice to drive again. Still work to be done, but it's much better.

 

 

I can't get over how clean it is inside.

[dollywobbler]

OMG ALL GERMUN KARS R RUBISH!

 

Getting seriously sacked off with the Merc. Changing a set of spark plugs should be a piece of cake. Easy. Pull lead off, unscrew plug, new plug, lead back on, job's done. Oh no. The M103 engine has its plugs located down long tubes, with long tubey plug leads. These seem to be welded to the sodding plugs for all the likeliness of them actually coming off. Special pliers appear to be powerless to get them off. It's just unnecessarily stupid. I've now got two destroyed leads, but the metal bits are still in place, so I still can't get the plugs out. New leads ordered but how the sodding bollocky chuff am I meant to get the old ones off?

 

I knew I should have bought VND's Jag.

[dollywobbler]

OMG ALL GERMUN KARS R RUBISH!

 

Getting seriously sacked off with the Merc. Changing a set of spark plugs should be a piece of cake. Easy. Pull lead off, unscrew plug, new plug, lead back on, job's done. Oh no. The M103 engine has its plugs located down long tubes, with long tubey plug leads. These seem to be welded to the sodding plugs for all the likeliness of them actually coming off. Special pliers appear to be powerless to get them off. It's just unnecessarily stupid. I've now got two destroyed leads, but the metal bits are still in place, so I still can't get the plugs out. New leads ordered but how the sodding bollocky chuff am I meant to get the old ones off?

 

I knew I should have bought VND's Jag.

[Rocket88]

Are the remants of the plug lead stopping you getting a plug socket far enough down to grip the plug? If so, an old fashioned box spanner might do the trick.

[dollywobbler]

No room to get a box spanner down there. It's tight. In the end, I opted to unscrew the remnants. Of the remaining four cylinders, one lead came off by hand with no bother at all, the other three needed unwinding. Not very good for the HT leads, but I'm replacing them all anyway. Stupid things.

[Rocket88]

Not one of their cleverer ideas.............pity the poor sods with AMG V12 Mercs.............24 of the bloody things. and it's about a 4 hour job, and a set of plugs is about £180!

[hairnet]

plugs down holes do suck

 

bikes are the same if not quite as fiddly - they have longer change intervals - makes them tricky sometimes

[Cheggers]

This may be why it's misfiring. I suspect the combination of expensive plug leads and the fact it's a right ball ache of a job means it's not been done for ages. Fingers crossed that sorts it for you.

[dollywobbler]

This may be why it's misfiring. I suspect the combination of expensive plug leads and the fact it's a right ball ache of a job means it's not been done for ages. Fingers crossed that sorts it for you.

 

That is my hope. I'll be watching the emission check come MOT time very closely to see what's going on. Was hoping to get the MOT done on Friday, but that's become rather dependent on the new plug leads turning up. MOT runs out on Monday.

[cort16]

Most W124's run like a swiss watch and have rusty bodywork. You seem to have found one the opposite way around, which is an achievement in itself. Hopefully the leads will sort it before it starts to get expensive.

[messerschmitt owner]

Progress. I weakened the idle mixture today and it now picks up much more promptly. There's still a misfire, but it seems more consistent so hoping new plugs and leads (the leads really are pretty dreadful) will cure that. The car is much more driveable - it no longer bogs down completely.

 

What is an annoyance is that I've had to order a special pair of pliers just to remove the plug leads. What a stupid design. I did pull one plug out after doing battle with the lead. It just looked well used. The gap was a bit too large - I think these are fussy about that - so for the first time in my life, I'm going to have to gap a set of plugs before fitting them. I'm not used to owning such a fussy car!

Merc do a special tool for deep seated spark plug leads - it's about six quid.

 

I have one for the smart roadster, which is resolutely refusing to start at the moment,

 

part number is mercedes-benz part number A 638 581 02 67

 

basically it is a T bar with a cut out and lugs to go over the ht lead so you can pull it off.

[Rocket88]

I weakened the idle mixture today and it now picks up much more promptly.

 

You may have to richen it again with new plugs and leads...................you may have tuned the mixture setting so it'll work better with knackered plugs and leads!

[messerschmitt owner]

http://www.smarttune.co.uk/product.php/ ... 6522bfc34a

 

link to the ht lead tool!

 

[dollywobbler]

I'm intrigued. How does that actually grip the lead then? Knowing me, the Merc will be long gone before the leads need to come off again anyway.

[messerschmitt owner]

The last bit of the cap is metal or plastic and it goes over and clips on to the cap and pulls it off.

[dollywobbler]

Yes! Success. I'll never know if it was plugs or leads, but changing both has improved things no end.

 

 

It has also been nice and sunny. Good all round. The Merc picks up superbly now and is nice and smooth whether hot or cold. I shall keep my smug face in reserve though, as there's still the small matter of needing to pass an MOT before Monday. Hoping to squeeze that in tomorrow afternoon.

[Cheggers]

Well done, it looks like a very dignified old lady.

[hairnet]

taxi mein herr??

 

good its sorted

[Spiny Norman]

Great to hear the old lady's finally driving like a Merc should.

[SambaS]

Pleased to hear you've fixed it! I was quite suprised it wasnt the distrubutor cap, we had one of these in the family for ten years or more and it was always serviced and repaired by a main dealer and went through more than a few of the things. K??? DEF iirc