low idle in drive

[rede30]

I have a little automatic that I have been cruising around. it runs fine and idles fine when in Park but when it is in gear and stopped it idles a little too low. Any ideas?

[LJ851]

Install the missing third pedal.

[Jafxod]

install the missing third pedal.

+1

[rede30]

maybe if it wasn't an ix. too much work.

[nando]

ix is less work. unbolt auto trans, put in clutch, master and pedals. bolt manual trans back in.

anyway, a low idle in drive could be a misadjusted TPS, vac leaks, dirty/non functioning ICV, etc. I'm sure jlevie will chime in about smoke tests, or you could do a search..

[rede30]

ix is less work. unbolt auto trans, put in clutch, master and pedals. bolt manual trans back in.

anyway, a low idle in drive could be a misadjusted TPS, vac leaks, dirty/non functioning ICV, etc. I'm sure jlevie will chime in about smoke tests, or you could do a search..

I don't see how it is less work, maybe equal but then there is the whole finding awd 5spd trans/t-case. Whatever the case, no swap will be happening. ICV was tested in a different m20. I will test the tps tomorrow. It does it hot or cold.

[xwill112x]

Maybe over expectations..? most auto cars dip down in rpms when at a stop in D.

[rede30]

yeah, they dip but it is a little too low, at least it feels like it. I had a different auto a few weeks ago and I didn't notice anything. It does idle rock solid when in park.

[bmwstephen]

How low r we talking about here?

[rede30]

Between 500 and 600.

[bmwstephen]

Normal on my car as well

[mr.vang]

Between 500 and 600.

that sounds right..

[nando]

that sounds right..

no it's not. the factory idle is 750 +/- 50rpm. if that's normal, your car is broken. if you put it in drive, the ECU will compensate by opening up the ICV a bit more, the idle shouldn't change and 500-600 is never "normal".

[rede30]

What else does the ecu do to compensate? If it is just the icv I should revisit that.

[nando]

it also adjusts timing to compensate for small changes in idle speed but it's not really directly related to the auto trans. there's no communication that tells the ECU what gear you're in, other than for trying to start the car. That's why it doesn't matter what ECU you have when you do a manual/auto swap.

basically the ICV can open far enough to idle the car at ~2500rpm. putting it in gear doesn't add enough load that the ICV can't compensate for on it's own. therefore, if it's idling 150-250 rpm lower than it's supposed to, something is not right with the idle control system.