PeachParts Mercedes-Benz Forum - CIS air flow potentiometer possible fix?

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

Quote:

Originally Posted by Marcel107 (Post 3520052)

When I see the solderjoints on the black one, I think it is junk and not a quality Item.

The colored one on the Top looks much better.
Regards from Germany
Marcel

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

Quote:

Originally Posted by optimusprime (Post 3520096)

Could you clean your air control valve.I use carburetor and injection spray . . And check all earth points , clean them up and put a little grease on them as you refit.Also check the vacuum pipes for holes .

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

Quote:

Originally Posted by 97 SL320 (Post 3520179)

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

...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!

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.

Quote:

Originally Posted by 97 SL320 (Post 3520319)

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.

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

Quote:

Originally Posted by Rob Pruijt (Post 3520672)

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)

Quote:

Originally Posted by 97 SL320 (Post 3520319)

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)