AC Idle bump

[nrubenstein]

Yes, the AC idle bump works. Hell, it works on my Euro motor with an MSS50. I can even see the DME report AC as on when I flip the AC button. It worked on my S50US as well.

[MC Hammered]

Troubleshooting this got put aside, the last step I was at was to determine if there is power getting to pin #9 and seeing if the software I have is correct or not.

[Wishno87]

So where are we at with this?

[328ijunkie]

E46's they started (somewhat) PWM compressors and stuff.
The E36 just uses basically 2 signals into the ECU, one from the 'AC button' and one from the pressure switches. When both conditions are met, it fires the compressor itself.

[jrez]

Been awhile since I looked at this(like 10 years) but I seem to recall the e36 dme gets a a/c compressor "on" signal from the climate control module, which I recall was not an analogue dc signal. Think it was square wave DC. The analogue(high/low pressure switches) on the e30 hooked into the e36 dme will do nothing to increase the idle. I tried also years ago.

[MC Hammered]

correct. driving is fine, it's only when you come to a stop that it hunts for a few seconds and then evens out...

still like to know how to eliminate that though...

I am having this issue as well and the hunt is almost like a timer is going off as I hear a click, RPMs drop and then recovers and this repeats. Odd thing is this does not happen all the time and is seemingly random.

Does your wiring setup look similar to mine? The pink/white wire is input to DME

[caesar101]

I seem to have my idle bump working on a OBD2 M52. I did not do the wiring on my swap so this is the first I looked at this problem. Violet/ gray wire from pin #16 was connected to the +12 a/c signal in the glovebox. Applying power on and off while idling did nothing. In the E36 the radiator fan is started by the a/c control and the same wire goes to pin # 16 on the DME by way of the pressure switch. To start the fan the control unit grounds this wire thus grounding pin #16. I installed a relay to ground pin #16 when power is applied to pin #19 and idle bump. It is not perfect but works much better. I am guessing the DME also delays the compressor start to allow the engine speed to come up first, but that would require wiring the compressor to pin #74 with another relay to start the compressor to test. I need some road time now to see if it is consistent.

[übersteuern]

Over time, the ECU learns the engine's running characteristics (eg rich/lean from the O2 sensor) and adjusts for it. Resetting the adaptions means it starts from scratch.

I had a mechanic do it, but I think there are ways to DIY.

[325e10]

On my M52 (running the OBD2 DME from an automatic car), I found that clearing the adaptions helped stabilise the idle heaps. Where before the revs would drop really low and sometimes stall, now it falls back to idle no problems.

Yeah it's a bandaid solution, but it does help a lot.

Adaptations? can you clarify that a bit more for me? not sure i'm understanding it.

[übersteuern]

On my M52 (running the OBD2 DME from an automatic car), I found that clearing the adaptions helped stabilise the idle heaps. Where before the revs would drop really low and sometimes stall, now it falls back to idle no problems.

Yeah it's a bandaid solution, but it does help a lot.

[Cynical 1]

Without the idle bump sorted?

correct. driving is fine, it's only when you come to a stop that it hunts for a few seconds and then evens out...

still like to know how to eliminate that though...

[325e10]

indeed. i actually used mine briefly last week when we had the 70+ degree day...

Without the idle bump sorted?

[Cynical 1]

indeed. i actually used mine briefly last week when we had the 70+ degree day...

[325e10]

hate to bump up an old thread - but does anyone have a difinitive answer yet as to the work around of the plug and idle?

agreed. 1+ - definitely solution here?

I'm still looking as well, though I made this thread. It turned cold so there really wasn't a reason for using the AC. But now that it's about that time for the temps to start rising. I want to do this right.

[r4esh]

agreed. 1+ - definitely solution here?