Bad day for me, engine cut out!!

[MBManInKen]

Ahhhh going up and up and up!

There's an appalling joke in there, but I think I'll pass .

 

[Dieselman]

It is a well known fault in the trade that on Motronic the mechanism on the idle change over switch wears. This switch is built into the throttle body and most of us just file away a piece off the stop, to allow the switch to close.

Shouldn't that just affect it at idle, which could account for the initial start issue but not driving..unless it cuts when the accellerator is released.

 

[television]

Shouldn't that just affect it at idle, which could account for the initial start issue but not driving..unless it cuts when the accellerator is released.

When the switch is not closing the idle can end up anywhere from too low so that it stalls or too high

 

[television]

Maybe.

But this is slightly different, it seems to cut out when traversing bumps..although the low idle could well be throttle body.

Hope not...£££££££

It could be the throttle pot wiper losing contact with the carbon track. a strip and clean may work.

We bought a body back in Sept last year, it was at the time the last one in the UK for a 124,,,,£1,330 if I recall correctly

 

[Dieselman]

When the switch is not closing the idle can end up anywhere from too low so that it stalls or too high

Yep, I know but thanks anyway.

what I meant was it would only affect it at idle condition, when running under power it shouldn't be an issue.

Is the car only cutting under idle condition..??

 

[television]

Yep, I know but thanks anyway.

what I meant was it would only affect it at idle condition, when running under power it shouldn't be an issue.

Is the car only cutting under idle condition..??

It depends on how you read the first post, when cruising up to a roundabout or lights, the engine is at idle

 

[Dieselman]

It depends on how you read the first post, when cruising up to a roundabout or lights, the engine is at idle

I understood that to, but thanks for clarifying, that's why I asked..if it was at idle..

What could be happening is the engine is running under 'running' mixture instead of 'idle' mixture when idleing.

 

[television]

It the OVP relay is involved here, and you have no means of measuring the voltage , just have the car idling and give it a whack with a screwdriver handle and see if the revs change

 

[television]

I understood that to, but thanks for clarifying, that's why I asked..if it was at idle..

What could be happening is the engine is running under 'running' mixture instead of 'idle' mixture when idleing.

If it cant switch over to the ECU idle, that would be the case, as everything is taken care of by the ECU.

I may be able to get hold of a Motronic book for MBs

 

[gina2201]

LOL..... if it is i better keep my keys safe otherwise Gina will be taking my car to the garage and swapping the bits over.....

Good idea!

Oh no, too late, I repsrayed both cars last night!

 

[gina2201]

Hmmm, so may not be a simple fix then after all?!

I shall have a look and maybe try a few suggestions!

 

[kth286]

Gina

Two things initially.

1. Seriously - is there "stuff" hanging from your key ring, in addition to the car key. If so take everything else off the key ring.

Now go test car at same places.


2. If it still cuts out, there should be a trouble code logged in the computer memory. You need to know an independent Mercedes (only) specialist that has the approporiate code reader.

It will take a few minutes to read the codes and get a conclusion to the problem.

It could well be the crank angle sensor in the bell housing that tells the computer the car engine is turning. It is the ONE vital sensor that stops everything. It reads the pulses from the flywheel when the starter starts turning the ring gear.

 

[gina2201]

Yes the car only does it when at idle, ie when stationary, braking or coasting. I'm just worried it may do it at higher speeds as then I really would be in a pickle.

Only the alarm fob and key on my keyring, no fluffy toys here! Drove it to and from work today, all ok and normal, will be able to see more/test when I go and see my horse as it's a longer drive, traffic lights, roundabouts etc etc

 

[Dieselman]

It probably won't cut at speed and if it does just select Neutral and start it back up whilst coasting.

Try it under power over bumps and also at idle, this will help decide if it's a bad connection or throttle position related.

Make a note if it's just as the engine comes back to idle from running and how much accellerator you had on before, etc...


Alternatively fit a horse yolk...

 

[gina2201]

Thought you could only start it in P?? It's ages since I've had an auto!

I shall test it later.....but it probably won't do it!

 

[Dieselman]

Deffo in N as well.

 

[television]

You can discount the ignition switch for this fault, if it was that, the lamps would all come on

 

[Dieselman]

You can discount the ignition switch for this fault, if it was that, the lamps would all come on

I might agree partially but why would the lamps come on if the ignition dies.?
Presumably they do as the engine stops.

 

[television]

I might agree partially but why would the lamps come on if the ignition dies.?
Presumably they do as the engine stops.

On the first key start they are all on, if it stalls only some come on, if the ign switch was intermittent they would all come on, further more if it was the switch it would do it at any speed

 

[Dieselman]

Agreed, that's why we needed to ascertain the exact circumstances. When posting about the switch I didn't know it was when at idle.