Mi16 Afm Idle Adjustment (ml4.1)

[SweetBadger 93]

My MI was not idling perfectly - kind of 'put put' from the exhaust every so often and the exhaust fumes smelt like it was idling a bit rich so I messed with the idle mixture screw to see what effect it would have.

 

Anyway first I wound it out (weakening the mixture I think) and there was a point where it was really rough but when I carried on going and wound it all the way out, it suddenly started idling perfectly. I'm guessing this is a fail safe (afm idle setting buggered mode) mode as when driving and lifting off the engine was kept at 1250rpm for about 5 secs before dropping to idle. Can anyone confirm this?

 

I've now adjusted the screw back in and it idles very well but still smells a bit rich on idle, really need it setting up properly on a RR but I'm toying with the idea of a new Catcams inlet camshaft so dont want to RR it untill I've made up my mind.

 

Can anyone recommend a decent RR near SW London, I've done a search but not really come up with much.

 

Thanks, Alex.

[jackherer 543]

I'd guess your initial idle problem was caused by an airleak somewhere, oil filler cap, dipstick, or the oil filler hose where it meets the block perhaps. I'd suggest checking those out before getting it setup or adjusted.

[SweetBadger 93]

I'd guess your initial idle problem was caused by an airleak somewhere, oil filler cap, dipstick, or the oil filler hose where it meets the block perhaps. I'd suggest checking those out before getting it setup or adjusted.

 

The oil pipes have seen better days but they're not easy to get hold of at the moment so I've stuck with them, I'm fairly sure there were no air leaks when I was messing with it. I haven't actually had the idle mixture properly adjusted since I put the MI in but yes I'd definately make sure there were no air leeks before taking it to be set up properly.

 

Was just a bit puzzled when I wound the idle screw on the afm all the way out and it started idling perfectly...

[jackherer 543]

the oil filler pipe can split where it goes onto the block and be very hard to spot, I've had that on several Mi16s lately and it causes exactly the symptom you've got, screwing the idle mixture right out is probably just compensating for it.

[SweetBadger 93]

the oil filler pipe can split where it goes onto the block and be very hard to spot, I've had that on several Mi16s lately and it causes exactly the symptom you've got, screwing the idle mixture right out is probably just compensating for it.

 

I was under the impression that screwing it out weakened the mixture, would I not have to screw it in/richen to compensate for an air leak...? If I've got that wrong then I think I'll have another go at it! It was probably not idling properly because I never got round to setting it up witht he new engine.

 

I think you may be missing my point though, the reason I thought it was a fail safe mode was because as I screw the idle adjuster out the idle gets progressivly worse and worse untill I reach a definate point where its like pressing a switch (i.e 1/8th of a turn) then the engine suddenly picks up and settles to a perfect idle. If I then turn the screw back in slightly the idle goes crap again, but if I keep going it gets progressivly better and is now idling spot on again. However when driving with the idle screw adjusted out over-run is affacted as when lifting off the ecu holds the revs at 1250 for a few seconds before settling to idle whereas with the screw adjusted in, the engine drops to idle very quickly when lifting off.