240 LH 2.2 Cold Idle Level?

Back from a long absence (sort of). I have used the LH 2.2 brains from a '86 240 B230F for an EFI conversion on my 1976 BMW 2002. All of the mechanical bits are BMW (intake, TB, Fuel Rail etc)

I've got it started and driving (goes like stink!). However, the M10 in the BMW would like a slightly higher idle than the 750 or so the computer wants to provide. I adjusted the TB stop to allow it around a 900rpm idle when warm and reset the TPS so it reads correctly. This works great, but when cold it still struggles a bit. Should the computer go to an elevated idle when cold (like say 1200 or so?), or after starting will it settle into normal "hot" idle? I'm trying to make sure the system is functioning properly before I start thinking of alternatives.

Thanks!
-Lloyd

Hi man,


Just flicking through and saw your post. I have a 86' 740 TIC with the 2.2


Its funny you should say cold idle system. I know the new volvos start with a high rpm to quickly warm up and then slow down after a minute or two.

Ever since I got my volvo 740 it idles high on cold just like the new ones and slows once warmed up. I was baffled because i didn't know the 2.2 had this feature?

My only suggestion is to rig up a vacuum system to a dash switch, controlling the idle unit. Hope I understood your question.

The car will maintain ~ 750 RPM cold and warm. If you want it to idle at 900 rpm there is a trick you can do, well not much a trick. There is an input for the A/C compressor on the LH2.2 ECU. When the A/C is turned on it sets the idle at 900 RPM. All it would take to do this is to hook up 12 volts to the A/C compressor input. This would be on the 3 pin connector that goes into the car for ignition & power to the ECU.

Do this, and the car will maintain 900 RPM Idle with complete idle control.

andysbeta said:

The car will maintain ~ 750 RPM cold and warm. If you want it to idle at 900 rpm there is a trick you can do, well not much a trick. There is an input for the A/C compressor on the LH2.2 ECU. When the A/C is turned on it sets the idle at 900 RPM. All it would take to do this is to hook up 12 volts to the A/C compressor input. This would be on the 3 pin connector that goes into the car for ignition & power to the ECU.

Do this, and the car will maintain 900 RPM Idle with complete idle control.

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Andy, you rock! That is exactly what I was thinking (hoping) would work. I just needed the second opinion! I'll report back.

Hooked up the A/C switch and it idles great now! Thanks.

Great to hear! I've done this too with LH2.2 cars when installing a "hotter" cam, 750 RPM just gives too much of an idle surge, 900 fixes that.

andysbeta said:

Great to hear! I've done this too with LH2.2 cars when installing a "hotter" cam, 750 RPM just gives too much of an idle surge, 900 fixes that.

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Yeah, the M10's don't like it to begin with. Add a big cam and you're hosed. I tell ya what, I'm really impressed with the system. It's a really nice match to the powertrain. The AFR's are solid all through...not bad for 1980's tech!