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WickedFast.Inc 12-05-2012 03:39 PM

Idle man idle just idle man
So i had an L shaped idle motor (wrong one for my car) it had a jumpy idle from the day i got it and if in park or neutral my car would I would 2000 rpm I bought a new motor and put it on in now when I start my car off it immediately goes puuuut and dies the only way i can seem to get it to idle is to adjust the screw on the monifold (a no no i am aware of ) otherwise it just kills over i am going to put the old one on because it ag least ran but do you have any ideas? And where is my tps

Wicked Fast Entertainment

hornhospital 12-05-2012 03:58 PM

Your tps is on the t. (throttle) Kinda obvious, isn't it?

WickedFast.Inc 12-05-2012 04:15 PM

Well that's what I was thinking but i didnt realize it was on the bottom i found it right after i posted. That said do you have any ideas? I was thinking my tps might be bad the tps tells my idle motor how far to open right?

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hornhospital 12-05-2012 04:42 PM

2 Attachment(s)
The TPS only tells the ECU if the throttle is open or closed. Follow this to test it:

WickedFast.Inc 12-05-2012 06:04 PM

Is that out of a bently manual? And why would my new idle motor not open? And if erratic idle is a syptom i may have a problem. When i stop the rpms wil jump from 750 to 1000 for a few and if i am at a long light it will eventually drop to 500 to 750 and so on until it is barely staying running it has only died from this once

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hornhospital 12-05-2012 08:31 PM

At 500 rpm it should idle smoothly even if that is a little low. Yes, those are pages from the E30 Bentley Manual. You REALLY need to get one. Erratic idle is almost always vacuum- leak related.

Nick323 12-06-2012 03:15 AM

TPS with built in Potentiometer
While we're at the TPS :)
Is there a TPS that will fit in the place of this E30 B20 unit that measures actual throttle position ? Like all civilised vehicles :tsk:

Oh yes, to get back to your problem. If the TPS does not see a closed throttle it cannot tell the idle motor to adjust the idle ;)

hornhospital 12-06-2012 08:24 AM


Originally Posted by Nick323 (Post 7233908)
If the TPS does not see a closed throttle it cannot tell the idle motor to adjust the idle ;)

^This exactly. It's an on or off switch, not a variable rheostat like the AFM.

WickedFast.Inc 12-07-2012 09:18 AM

And from what you showed me HH, it should read no resistance when closed right?

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hornhospital 12-07-2012 10:59 AM

Correct. Continuity means zero resistance. 0 ohms. It's really two switches in one housing. It tells the ECU it's either a closed throttle with one switch, or a wide open throttle with the other. In between (throttle part-way open) it should have infinite resistance between the center contact and either of the outside ones. When the throttle is closed, the idle side turns on the idle control valve (through the ECU). If the TPS is bad or adjusted incorrectly, the ICV can't regulate the idle.

WickedFast.Inc 12-08-2012 10:27 AM

I get infinite resistance closed and all the way open but in between i get resistance

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hornhospital 12-08-2012 04:09 PM

That is completely backwards from what it's supposed to be. You should have continuity (zero ohms resistance) between pins 2 and 18 with the throttle closed, and continuity between 3 and 18 with it wide open, and that's all.

woodenbmw 12-08-2012 05:03 PM


Originally Posted by hornhospital (Post 7233524)
At 500 rpm it should idle smoothly even if that is a little low.

What is the normal idle speed ? Mine will idle at just under 1000 rpm in park, but drops to about 650 rpm when I put it in gear.

WickedFast.Inc 12-08-2012 08:38 PM

500-600 told she should sound nice and purrty

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woodenbmw 12-08-2012 09:43 PM

Any idea on the drop in idle speed when put into gear ?

hornhospital 12-08-2012 10:10 PM

Wooden, is it an automatic? If so, that's normal, since the torque converter loads against the engine.

Sent from my MB860 using Bimmer App

woodenbmw 12-08-2012 10:36 PM

Hh, it is an automatic. I suppose that would explain it. So, does that mean I should idle faster in park ? Or should the idle still be in the 500 - 600 range while in park ?

hornhospital 12-08-2012 10:40 PM

It'll idle a little higher in park or neutral since there's no load. Perfectly normal.

woodenbmw 12-08-2012 11:17 PM

I'll shoot for the 700 - 800 range then. Thanks for the info. Am I supposed to set the idle using the set screw on the ICV ?

hornhospital 12-09-2012 01:28 AM

1 Attachment(s)
Not really.

Read the last paragraph:

woodenbmw 12-09-2012 11:32 AM

Oooops. Looks like I need a new one. Unless there's a way to know where the set screw is supposed to be. I've been fiddling with it since I got the car a few months ago. My idle was around 1300 rpms and I had to slow it somehow...

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