W124 E280 Surging

[laverdakeith]

I wonder if anyone can help. My 1995 E280T has developed a slow running fault. When comming to a halt the engine sometimes surges rather than calmly dropping to idle, not all of the time but more often than not. On stopping the car the engine revs fall and rise above and below the normal rock steady 600rpm idle, the revs kind of bounce above and below the correct idle speed then eventualy settle as if something is undamped. The engine never stalls and after a bit of a bounce it settles into a smooth tickover.
I fitted a new engine wiring loom last year, it has three new Bosch coils, new leads and under coil connectors. In all other respects the motor is smooth and powerfull and returns around 32 to the gallon on a steady run, which it always has.
Any ideas?

Thanks. Keith

 

[brianbrian]

Have you checked the timing hope this helps

 

[meanie]

My first thoughts are that you have a slight air leak.
Next,smegged up throttle body.

 

[che124]

Hi, I am new to the forum.

I have just bought myself a W124 E280. It has 110,000 miles on the clock and is in pretty good condition.
I have recently been having the same problem with the hunting idle, although it is an on off thing. Today was driving in London and it was fine for 1-2 hours in and out of traffic. Stopped for 1 hour got back in the car for the return journey and half way though started hunting idle while I was sitting in traffic. Stalled a total of 4 times but always started again with a little gas.
The idle hunts between 500 and 700 and then stalls, unless I put it into neutral, at all other time it runs perfectly. Will be giving it a good service and checking connectors when I do.

 

[rpe2]

Throttle body gummed up. Happened on my old W124.

 

[Alex Crow]

Throttle body gummed up. Happened on my old W124.

i was going to say that richard!! if when starting the engine the rpm initially dips right down then recovers, this confirms the diagnosis. carburettor cleaner is the best product to clean it. other possibilities are stuck purge valve or something else. nice vague finish there, hedge those bets...

 

[kth286]

Yes - the purge valve on the NS inner wing with MOT on top of it.

See if it is ticking about twice per minute.

You can normally feel it and hear it.

It needs the engine hot and started for a few minutes before it will start to pulse.

It removes the fumes from the fuel tank and they can gum up in the open position, allowing fumes to be drawn into the engine at times when they should not be.

About £90 ish pounds or may possibly be able to be cleaned out (not many reports of that).

 

[che124]

Thanks guys,

Ill try carb cleaner on the throttle body first, then look into the purge valve.

I will post the results.

 

[STEVE333]

surgin'

Hi All,
I too have a surging 124 E280, which missfires as well, although under load
it runs fine!?
I get code 33 from my tester, which will not clear?
Any suggestions greatfully appreciated!

 

[chardF]

Hi chaps,

I've had an intermittent rough idle when warm(more of a flutter really) feels like a vacuum leak. Whenever it occurs a "lambda operating system rich or lean" code is generated.

I can't find anything wrong with the vacuum system, all pipes and connections secure and tight.

I took the purge valve off and with a bit of sucking and blowing I can get air through it. Seems intermittent though, sometimes it holds a vacuum sometimes not. If I connect up 12v DC to it, it snaps open smartly, disconnect power and it stays open for a minute or two, slowly closing. Even when closed I can suck/blow and it won't hold a vacuum.

Anyhoo, I blocked the pipe to the charcoal canister and the vacuum pipe to the inlet manifold. The idle seems to be about perfect, however due to the intermittent nature of the fault I'm not declaring success yet.

Will it do any harm leaving the pipes blocked for a bit to see if it's fixed the problem?

 

[hotrodder]

Hi chaps,

I've had an intermittent rough idle when warm(more of a flutter really) feels like a vacuum leak. Whenever it occurs a "lambda operating system rich or lean" code is generated.

I can't find anything wrong with the vacuum system, all pipes and connections secure and tight.

I took the purge valve off and with a bit of sucking and blowing I can get air through it. Seems intermittent though, sometimes it holds a vacuum sometimes not. If I connect up 12v DC to it, it snaps open smartly, disconnect power and it stays open for a minute or two, slowly closing. Even when closed I can suck/blow and it won't hold a vacuum.

Anyhoo, I blocked the pipe to the charcoal canister and the vacuum pipe to the inlet manifold. The idle seems to be about perfect, however due to the intermittent nature of the fault I'm not declaring success yet.

Will it do any harm leaving the pipes blocked for a bit to see if it's fixed the problem?

Blocking off the line from the purge valve to the charcoal cannister is gonna mess with fuel tank venting and not a good idea. Disconnecting the line from the valve to the inlet manifold and blocking the inlet manifold side is fine until you fix/replace the valve
On the off chance you're not already aware http://www.w124performance.com/service/Index/104/47FuelSystem.htm 47-0030 and 47-0200 explain how the tank vent & EVAP system works

 

[chardF]

Thanks for the diagram. I blocked the charcoal to purge valve pipe because I didn't want fumes venting into the engine bay.

So the only temporary solution is to vent from the canister into the wheel arch, not ideal. Do these generate a lot of vapour? I'm guessing less in winter than summer.

 

[chardF]

The valve is a fairly simple device. Do I need to be anal about part numbers or would any MB valve that fits be okay? I'm thinking early C Class or something.

 

[chardF]

I think the valve has defiantly had it. It opens smartly when you apply 12v, then takes 15mins to close and seal. I've ordered a used part, I hope it's better.

In the meantime I've left the intake tube blocked and routed the tube from the charcoal canister under the car. I don't want it to vent into the engine bay.

 

[hotrodder]

Thanks for the diagram. I blocked the charcoal to purge valve pipe because I didn't want fumes venting into the engine bay.

So the only temporary solution is to vent from the canister into the wheel arch, not ideal. Do these generate a lot of vapour? I'm guessing less in winter than summer.

Cheers, yeah more vapour on a hot summers day. I wouldn't worry about leaving the vent 'open' for any length of time personally... for eons that was how car fuel tanks were vented and it only changed for environmental reasons. At the fuel tank end of the vent line there's still a two way check valve and an elaborate baffle system in the tank whereas in the old days the vent was just a small diameter hose in the top of the tank or it's filler neck often with no check valve at all

 

[chardF]

New valve on, nice smooth idle now.