124 280TE Rough running

[Hurm]

After searching the planet I have managed to get a good used wiring loom! All installed and I now have a 6 cyl mercedes instead of 4 and a bit. However before I start pulling things apart I thought I would ask "the knowledge" here what to look for: Engine starts but struggles to maintain an idle. The first inch of accelerator pedal travel doesnt do anything and then hello 2000rpm. The engine seems to surge between 400 and 1000rpm or it just dies. The MAF looks brand new and is spotlessly clean. If I disconnect the MAF with the engine running the idle improves but only very, very slightly and the engine still dies. If I get throttle happy the rev limiter cuts in at 4000 (is this right?).
Any ideas on what to start with? I would like to be able to monitor the O2 sensor but where are the wires accessable or is there somewhere I can get multi meter plugged into it whilst its connected.
Any help appreciated and before someone says get over to your local stealer and have the codes read I need to get it running for the MOT which unfortunately expired.
Thanks all - Hurm

 

[television]

your car 124--- next 3 numbers please.

 

[Hurm]

Chassis No:

Malcom, the car is WDB1240882F238289.
Thanks

 

[Hurm]

Oops

Sorry Malcolm - spelt your name wrong......Im currently doing penance trying to get a damn Ford Fiesta going !!!

 

[television]

Do you know what injection system that you have on the car. KE,LH, or motronic.

 

[Hurm]

Type

Malcolm,
Im certain its the Bosch HFM setup

 

[television]

Malcolm,
Im certain its the Bosch HFM setup

I will turn on the other computer shortly, thanks.

 

[television]

Got one. Engine surges when idling and in D


Engine sucks in leak air through regeneration valve (sticks sometimes)

fault codes 034,028 and 061 Check regeneration valve ,replace according to condition.

I do not follow this bit.

knock out to check whether carbon particle residues are present in the regeneration valve, if so check lines and activated charcoal filter and replace according to condition.

 

[Hurm]

Hmmmm

I understand removing the valve and banging it on a hard surface to see if theres carbon bits in it but.... regeneration valve? Plus this surges in park as well as drive. I was thinking more on the lines of idle control circuit etc...but then what I know about this system you could write on a postage stamp!!

 

[Hurm]

Valve?

I understand removing the valve and banging it on a hard surface to see if theres carbon bits in it but.... regeneration valve? Plus this surges in park as well as drive. I was thinking more on the lines of idle control circuit etc...but then what I know about this system you could write on a postage stamp!!

Would this be the EGR valve by any chance?

 

[television]

Ok, I have some knoweldege on some of the components.

The EGR valve if sticking will give a rough idle, as it should be closed at idle.

Other parts.

All of these things run in a similar way. Where there is an idle relay fitted, any fault in this part will switch the engine over to the fail safe high idle off the main computer ECU naimly 1k where there is an idle relay fitted the engine idle is also switched on the gear shift when going to D

I do not know if the throttle on yours is electric,as on the early C class if it is then on the throttle butterfly there is an idle contact switch that wears, these contacts when worn will send the idle as I said earlier to over 1k off the main ECU. the remedy here is to file the contacts of the switch linkage to allow them to close.

One can also program the PCM using the ignition switch.

 

[kth286]

Whilst the car is all electronic control it may not have a drive by wire throttle
as that was limited to the models with ASR traction control.

Does your car have ASR ? - is there an indicated light in the speedo for ASR.

I suspect it probably does not therefore you would have a normal throttle cable linkage.

Also, not all cars had the EGR facility (mainly in States I think). My similar UK spec car does not have EGR valve etc.

Could well be the charcoal canister never been changed, which is a service item at 72000 miles.

Also lambda probe in exhaust; and perhaps water temperature sensor (cheap) which provides a critical input to computer to control the engine's revs as car warms up.

 

[Hurm]

This one definitely does not have ASR and is not fly by wire throttle. I hae yet to check if it has and EGR fitted but will let you know later. I have a feeling Im looking at changing the lambda sensor as I cant really monitor if its working or not. I think I will order one up and get it changed anyway and see what happens.