Lumpy idle and dead spot

[Smellit]

This is for a friend, he has an 1989 m20b20 engine and its idle is a bit lumpy (v8 like) and almost cuts out when you try to rev just for a second then revs up ok. if you hold the throttle about 1mm open it tries to cut out?

No air leaks
idle control valve fine

Im betting its the tps so going to check this for him but thought i would throw it on here to see what people think?

[Speedtouch]

Try resetting the ECU by disconnecting the battery for an hour or so, then let it idle for at least 10 minutes to enable base idle settings to be learnt, then switch off, restart and take it for a drive throughout the rev range.

[Brianmoooore]

Same as always. Air leaks, possibility of messed about settings that shouldn't be touched (TPS, throttle stop and AFM), and injectors badly in need of a rebuild.

[Smellit]

Sorry forgot about that, did the ecu reset, thought about injectors too but had a second set that make it run exactly the same? Also changed the blue fuel temp sensor as had a brand new one in the garage
As far as im aware nothing has been fiddled with as its my old engine and i bought the car off of an elderly gent who regulary had it serviced throughout its life at bmw.

Have a spare engine so have been swapping parts about to see if it makes a difference but nothing has and the only thing left is the tps.

[Speedtouch]

Have you tried cleaning out the ICV of fitting a spare one?

[Smellit]

aye icv swapped no difference and the one on was cleaned by me when i had it, going to try the tps tonight.

[Grrrmachine]

My money's on an air leak.

[Smellit]

I hope its not an air leak, we have hunted and hunted for an air leak, had all the vaccume and inlet pipes off, easy start round any joints on the inlet etc.

Its just either the tps or one of the parts we swapped by sheer pain in the arse being as buggerd as the original.

even compression tested it to see whats what there but all square and good.

[Smellit]

Just had a little brainwave, the brake booster pipe thing didnt look none to healthy and didnt check this

[Grrrmachine]

Did you check the rubber bung/pipe to carbon cannister under the throttle body?

http://www.e30zone.net/e30zonewiki/inde ... #Air_Leaks