hello, I've had this problem since my automatic days, but now its becoming a slight annoyance since my car is now manual.

when I am driving the car, as I am coming to a stop I push the clutch in and the engine revs will sometimes fall straight to 0, instead of dropping to around 500rpm and bouncing up to idle.

I had this problem when my car was automatic too, but no one knew what was wrong. coasting down a large hill in drive, then drop into neutral and the engine would stall.

I tried fixing this problem this weekend by replacing my OVP relay, microswitch, readjusting the throttle linkages and lubricating them with ATF, removing my IACV and sprayed it out with air intake cleaner, new O2 sensor, fuel mixture is set properly, IACV hoses recently replaced.

any other suggestions?

just pushing the clutch in, no throttle input at all?

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1992 850i 6 speed
1991 M3 S54B32 swap
2007 328iT/6 RWD sport wagon
1987 325E 330iZHP engine swap
2004 Vespa 200GT
1976 W115 240D getting a much bigger engine. 5.5L
1997 R129 SL600 5AT

I know you say you have cleaned the IACV. But it could be sticking. I struck this once.

Have you got a known good IACV you can swap ?


I can't remember that engine as it has been a while. But if I recall you can try unplugging various items to see if it influences the drive.

IE unplug the IACV and see if the symptoms disapear. It wont run great like this. Also if I remember you could do the same with the EHA... Not sure if this could be related though.

no throttle input, just coasting down towards a stop, then pushing clutch in around 2000rpm or so, and the revs just fall straight to 0.

I don't think the IACV is sticking because I ran 12V from battery through it in both directions through the terminals and it was clicking and turning the flap inside

weird. try disabling the clutch safety switch and see if it does the same thing.

__________________
1992 850i 6 speed
1991 M3 S54B32 swap
2007 328iT/6 RWD sport wagon
1987 325E 330iZHP engine swap
2004 Vespa 200GT
1976 W115 240D getting a much bigger engine. 5.5L
1997 R129 SL600 5AT

it is disabled, I converted the car from an automatic so it is not used for anything. this problem occured with automatic transmission too when putting car into neutral while coasting, so it has nothing to do with my manual conversion, something with my motor.

wow. um. yeah, I really have no idea what that could be! vacuum leaks or a going bad fuel pump are my only ideas but that really doesnt add up

__________________
1992 850i 6 speed
1991 M3 S54B32 swap
2007 328iT/6 RWD sport wagon
1987 325E 330iZHP engine swap
2004 Vespa 200GT
1976 W115 240D getting a much bigger engine. 5.5L
1997 R129 SL600 5AT

i have 16'' of vacuum at idle, and vacuum seems to be right when I drive around town. dont think its a bad fuel pump either because I can hit high RPMs real easy.

only thing I can think of is maybe because of my bad headgasket or fuel pressure regulator.

What difference does it make to the idling if you lean out the mixture a quarter turn , CCW or by enriching it.


mak

so i replaced my headgasket, and problem is still here.

I tried disconnecting the IACV and what happened was that the car was hard to start and idled like crap. idles at 500rpm almost stalling with IACV unplugged, and when I plugged it back in, car started up just fine and idled normally.

is this normal behavior of IACV unplugged? i thought it was supposed to idle high.