Is this a 0.1 V variation while running? The air plate can be bouncing around by that much with a rough idle.

Doesn't surprise me (but I don't think it is broken just yet!)

Thanks I've done that a few times already...

...I'm convinced the problem is electrical - mechanically the system seems to be in good condition.

Bought a new Oxygen sensor - I know I've said it before but it really is the last effing thing I'm going to change!

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

A rough idle can cause intake manifold vacuum to vary and the plate to bounce / voltage to vary making this a symptom not a cause.

Try holding the air flow plate in a state and see what the idle does. Also pull it open a bit ( makes the mix rich ) and close it a bit ( makes it lean ) and see what the results are.

I'm 90% sure this isn't happening but now you've brought in an element of doubt to my recollections. I will check and see if it is happening.

I still think the air idle control valve is the one at work (supply at bit of extra air) trying to keep up with the changing electrical signal.

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

In the Netherlands you can buy the origanal part at any Bosch dealer.
I don't know the current price but a few years ago I paid € 20 for an original Bosch at Primaparts.

Rob

Thanks for the tip Rob.

I get feeling times have moved on though.

See for example =>

Zoekresultaten | MijnAutoOnderdelen.nl

(These people are at the moment about the cheapest - not always - but you know how it goes - shop around and ye shall be rewarded)

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

I've just been outside to play.

I've replaced the oxygen sensor and the signal at the air flow potentiometer is now steady.

I thought my adjustment of the throttle linkage (seemed like an oversight when I put the car back together) had solved the sudden stall issue. This is not the case. By a process of elimination the EHA looks like it is going to be the next port of call.

The idle is steadier - but there's a feeling of a bit of lumpiness once in a while - there is a bit of variation.

The duty cycle readings are varying by about 4%

Mechanically the mixture unit seems to be rock solid: The air plate doesn't move (with the idle fluctuations)

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!