W124 tickover & external temperature sensor

[steve moores 1]

Chaps

Perhaps you could help with these two niggles?

On the '95 model W124 (220) coupe, was the external temperature sensor an extra at time of original sale or is mine simply not working? The slot appears black in the dash in between the other warning lights.

Also, when idling at say traffic lights, the rev counter initially stays at approx 750, then after a small while the rev counter drops to approx 450 - 500 as though it is being suffocated then recovers to 750 again; only to repeat this 3 or 4 seconds later continuously. Not wanting to sound too stupid but is there an easy fix for this? :roll:


Thanx

Steve
'95 E220 Coupe

 

[talbir]

If the slot in the instrument panel appears black, then you do not have the temp sensor option fitted. If the exterior temp display unit was there, it would appear a light greyish colour, even with nothing switched on - and that space would light up at night when you switch the lights on, since the display unit is illuminated along with the instrument panel dials. I think it was always an optional extra.

On the idle, it could be a few things - you need to do a step-by-step check. My first guess would be a blocked or dirty fuel injector not releasing a full spray pattern - everytime the cycle returns to that cylinder with the clogged injector, the engine is stuttering.

How does the car drive ?

Does this problem occur on cold, hot or both ?

Try momentarily disconnecting the vacuum pipe from the ignition ECU unit, which is on the nearside engine bay firewall. The ignition ECU has 4 inputs, 2 multi-pin ports, one single pin port which takes a feed from the crank position sensor and the 4th input is the vacuum pipe from the inlet manifold. The ignition ECU uses the vacuum to retard/advance ignition timing - and sometimes removing this pipe for a few seconds will remove the stuttering idle. If it does, then you need to investigate further - it could be that the ignition ECU assy is not functioning fully w.r.t. to the retard/advance mechanism for the timing.

 

[mjtray]

Idle problems

Steve,

Just posted a message that may be relevant to you.

I also have an W124, which suffered a similar problem. Turns out that the throttle body had a build up of carbon in it which creates a small air leak, which then causes the idle to flutter.

My local independent cleaned the throttle body and its now got a rock solid idle.

Hope this helps.

Cheers

Martin

 

[steve moores 1]

Thanks for these leads chaps. :wink:


Steve