Mi16 XU9J4 idle mixture wont adjust

[jackherer 543]

I've been trying to set the idle mixture on a friends Mi16 engine, when I had it hooked up to an MOT emissions tester the numbers didn't change at all when I turned the CO pot on the AFM. The AFM is brand new but non genuine so I naturally suspected it was faulty. However when I put a meter on the terminals of the AFM and turn the screw the resistance varies and I've now compared it to a used Bosch AFM which behaves the same.

 

My next thought was that the TPS might not be switching to idle and this might prevent the CO pot from being part of the mixture calculation but it tests OK as does the wiring between the AFM, TPS and ECU connector.

 

I'm now thinking the throttle body might have the typical wear that Mi16s suffer from, when I hold the linkage tight the idle cleans up and it sounds like the mixture is changing when I adjust the CO pot although it's hard to be sure without putting it on a gas analyser.

 

Has anyone else had an Mi16 (or any early Motronic based system) that wont let you adjust the idle mixture via the AFM screw?

[Ju4nD6C 0]

On 20/12/2017 at 11:06 AM, jackherer said:

 I've now compared it to a used Bosch AFM which behaves the same.

 

can you remember wich one?

[jackherer 543]

Part number 0 280 202 202

 

I forgot about this thread, I did get this resolved and I think it was the worn throttle body letting too much air in which was stopping the ECU going into a mode where the idle mixture is adjustable via the CO pot.