Mi16 High Idle

[davemar 16]

My 205 has a 1.9 Mi16 running with the Motronic setup. For a while now the idle when cold has gone very high, often around 2.5-3k. When warm it does drop down, but rarely to a nice steady 900rpm, often around 1.2k.

 

To try and give some clues I've just run the engine when cold:

- Without touching anything it idles around 3k.

- If I disconnect the idle control valve electric supply the idle drops a bit to around 2k.

- If I have the idle control value supply reconnected, but clamp shut the hose feeding it, the idle drops right down to below 1k and pretty much stalls (obviously still cold, so wants some more revs).

 

Does this suggest an idle control valve problem, or something else?

 

The throttle switch clicks, but I haven't had the chance to test it's connectivity.

The temperature sensor seems to read sensible resistance values.

 

 

[petert 586]

TPS micro switch faulty. Clicks but contacts can be broken.

[jackherer 543]

The very high idle will be the TPS not working as Peter says. If you solve that and it still intermittently idles a bit high, e.g. 12-1500, you probably have some wear to the throttle body too.

[Tom Fenton 1,541]

Easy way to test, unplug the plug from the throttle switch, bridge the pair of wires for the idle circuit. If the engine then drops down to 900rpm idle then the switch is faulty as said above.

[davemar 16]

I'll give it go when it stops raining!

[davemar 16]

It turned out to be a rough connection on the throttle switch. Pulled it off, gave the contacts a rub and replaced it, and now seems to idle at a more sensible level. Only just checked when cold, so will need to take it out for a run to double check.