M20b25 Running Rich / Failing MOT emissions test

Thu Jan 01, 2015 9:35 pm

The idle switch is the miniature microswitch on the right of the pic. If a small amount of thick oil gets into its casing, it will act as an insulator between the closed contacts (still clicks), and when more oil gets in, it will gum up the mechanism and stop it switching altogether (no click).
As can be seen, the WOT switch is much simpler, and less likely to fail, or be affected.
If you are sure that there is no continuity between pins 1 (brown/blue) and 2 (brown), when the throttle is closed, then it's essential you find out why.

Fri Jan 02, 2015 2:45 am

Brianmoooore wrote:The idle switch is the miniature microswitch on the right of the pic. If a small amount of thick oil gets into its casing, it will act as an insulator between the closed contacts (still clicks), and when more oil gets in, it will gum up the mechanism and stop it switching altogether (no click).
As can be seen, the WOT switch is much simpler, and less likely to fail, or be affected.
If you are sure that there is no continuity between pins 1 (brown/blue) and 2 (brown), when the throttle is closed, then it's essential you find out why.

The TPS is fine. I've just made up some cables for my multi-meter with spade connectors on the ends so i could get better contact on the terminals.

WOT Pins 3,18 - OK

Closed Pins 18,2 - OK

Tue Jan 20, 2015 10:22 pm

I've given up with the Motronic

Thu Jan 29, 2015 12:21 pm

Did this ever get solved?

Thu Jan 29, 2015 12:23 pm

Not really, I think the ECU was faulty as I'm going down the MS / wasted spark route I wont ever find out

Tue Feb 03, 2015 8:48 pm

Hi JakeusSnakeus, feel for you.

Bit of a long shot but I had similar problems in the past and took mine to a bosch specialist who couldn't find the problem until his shirt cuff caught on the afm top cover and it lifted off....it had been bodged previously as this shouldn't come off. Changed the afm for a scrap dealer unit which fixed the problems.

Give the black cover a look/try to see if it has been removed before. In mine the arm which sweeps across all the contacts to give varying resistances had been 're-set' and the arm poorly secured (screw glued on) by some numpty earlier owner.

Good luck.

Sat Apr 11, 2015 8:49 pm

Thanks man, i really did want to find out but here's where I'm at now:

http://www.e30zone.net/modules.php?name ... 16#2836616