W124 e300d intermittent rough idle

mattc

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So I have the above vehicle. Drove it for an hour today, can to restart it and the power was OK for a minute then went very weak. Very rough and I could feel it falling with blueish smoke coming out the back. Limped the car off the road and called recovery who are in there way.

Tried the car a few times and it was still running rough but now it's running fine again. Will still get it recovered as don't trust it not to fail again on a fast country road back home.

Any ideas where to start looking?

Don't know if this is related but the wash wiper was playing up too just before. Indicator worked fine though.

Matt
 

91dm

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Is it a 95' with the 24v engine, black plastic top?

Does it clear with a rev and only runs rough on tick over? How much fuel was in the tank at the time? The fuel line seals do give trouble and let air in, not a major issue.
 
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mattc

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Is a 96 one so yes.

Rough idle, would not rev and stalled when put into gear. Waited some time then it started fine, ticked over fine on idle and revs freely.

Tank about third full
 
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mattc

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Update. Was recovered back to a local garage. The car started fine and was driven on to the low loader ramp. The recovery man opened the drivers window which would then not go up again. So now the wipers front and rear do not work and none of the windows... looking like something on fuse board I am guessing. Let's see if they can isolate it tomorrow.
 

91dm

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Get them to check the simple things such as battery, leads and earth strap.
 

Smiley

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As already said the most likely cause of poor running on this engine is air getting in to the fuel supply; there are a number of clear plastic fuel delivery pipes with small seals that go brittle over time. It is worth changing all of the seals/pipes. It is also worth checking the fuel pre filter and make sure that the o ring on the end of it is in place - a new o ring does not come with a new pre filter and can be overlooked. If you are still having problems then there is a filter in the base of the fuel tank itself. It is fairly unlikely that this filter will be blocked unless the car has been standing unused for a while and is suffering from diesel bug which causes an algae to grow in the diesel and blocks the filters.
 

ChipChop

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A potential easy fix as mentioned above is the pre fuel filter and the main metal canister fuel filter. If you have never changed them then do so. Easy job, fill the metal filter with diesel before fitting. If you have changed the metal fuel filter recently then the filter may have been overtightened causing the central rubber seal to distort and block the fuel flow. A quick diesel sniff test (with your nose) will let you know if your engine is leaking diesel from the injection fuel pump delivery seals which if leaking can cause air to get into the fuel system. MB fitted clear fuel lines near the main fuel filter so you can see if there are air bubbles present. MB main dealer can supply the injection pump delivery seal o rings and copper washers for around £20 but you will need a special splined socket to remove the IP hardlines.
 
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mattc

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Latest update.

My mate who owns the garage had a quick look, cleaned some fuse holders and got the windows working again. The car is running fine right now so I plan to pull each fuse and clean the contacts and grease them v lightly with vaseline. I think I will also pull the relays i can easily access and clean them with a v fine steel wool.

As bad luck would have it we are just in the process of moving so my Haynes is packed away in one of a couple of shopping containers. Could really have done with the wiring diagrams. Timing is typical. At least I have the estate back to carry on ferryng stuff to the containers.

I will let you know how I get on and if cleaning the contacts helps things to work again
 
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mattc

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Update.
Mono wiper working again but no wash spray.
Rear wash wipe not working
Rear demist working
Windows working

Edit- driven it just and no signal or horn.

Dirty contacts really is starting to look the culprit. Need to give everything a thorough clean.

Not cleaned everything and intend to pull the relays and connectors and clean those next
 
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Smiley

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iirc there is one relay that is problematic on the 124; it is under the cover near the fuses on the driver side under the bonnet - it controls the indicators and wiper from memory - I bought a new MB one for mine and it was a lot of money even 15 years ago. I think that it suffers from dry joints internally - I did manage to make mine work (whilst I waited for the new one) by wedging a piece of cardboard between the edge of the relay and the housing that it sits in. It is also worth replacing all of the fuses, cleaning the contacts and checking for any overheating. I was starting to see those sort of problems on one of the cars when it was about 10 years old.
 
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mattc

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I think that's the N10 relay you are referring to. I will check that when I have a spare hour or 2 (which is not at the moment as packing everything up to move house...cracking timing
 

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