W124 M103 Cutting Out
 

Recently my 300E has started to cut out (but not stall) when i am driving and intermitantly surge when idling. This occurs regardless of air temp but normally when the engine is over 80 degress celcius. I have disconnected the idle air slide and the problem dissapears. Last night i fitted an air slide from another vehicle and although the problem has not been fixed, it's severity has halved. I suspect the slide even though a mechanic at work who has repaired these cars since their lauch says i am barking up the wrong tree.
I have tested all the usuals, fuel pump, fuel pump and over-voltage relays, air-flow meter, coolant temp sensor, ignition leads, distributor and rotor button.
Any assistance/advice is well appreciated

Oh, I am a new subscriber but long time reader of this post and when i can find a reasonably priced m119 then the first right-hand drive 500E will be born!

Andrew:

Idle valve will not cause the engine to miss at speed, only causes idle speed irregularities at idle, and can cause a stall if it sticks during hard braking.

If you get surges and thumping rough idle, check the current through the valve (you will need a meter that reads 1A DC) -- if you get intermittant low (300 mA or so) "twitches" the OVP is shot and needs replacement or repair -- current isn't being controlled by the speed control circuit, but by bad power supply via the OVP.

Intermittant loss of power under load CAN be the OVP, though -- low current will cause the EHA to vary the mixture improperly. This will be worse if the fuel distributor is set incorrectly.

I'm going to have to check the 300TE, I suspect my rough idle and performance problems are from the OVP -- it gets very hot in operation, and it's the original 1 fuse type.

PEter

Thanks for you reply,
I have borrowed an ecu from a friend and found that all problems disappear (although idle is rough, i suspect injectors).
I have also ordered new idle valve hoses.