High Idle

[Vince30]

My 86 325es idles at about 700rmp when it is cold but as it warms up it gets up to 1200. It seems really high and my guess would be a thermostat problem. But is there a sensor or something i should look at first?

Thanks,
Vince

[twright]

My car did that when the TPS (throttle position sensor) was not adjusted correctly.

[87e30]

Oh weird. I searched and just made a thread covering a similar problem. Woops!

twright: more info on adjusting TPS?

[jlevie]

With the engine at normal temperature the procedure for adjustment of the TPS is:

1) Disconnect the ICV and adjust the throttle stop for an idle of 900-950rpm.
2) Adjust the TPS so that the idle switch closes (as shown by an ohm meter or test light) when the throttle arm is 0.030-0.060" off the stop screw.
3) When the ICV is reconnected, idle should stabilize at ~750rpm.

[nando]

With the engine at normal temperature the procedure for adjustment of the TPS is:

1) Disconnect the ICV and adjust the throttle stop for an idle of 900-950rpm.
2) Adjust the TPS so that the idle switch closes (as shown by an ohm meter or test light) when the throttle arm is 0.030-0.060" off the stop screw.
3) When the ICV is reconnected, idle should stabilize at ~750rpm.

Have you tried this? setting the idle RPM to 900rpm with the ICV closed/disconnected doesn't sound like it would work. Because now the computer wouldn't be able to drop the idle down any further (since the ICV is already fully closed). Unless the ICV stays open when you disconnect it?

[Vince30]

Can I get more details on adjusting the TPS? I dont see anything about that in my Haynes manual.

[twright]

Adjust the TPS so that the switch activates (you can hear it click with the engine off) when the throttle is just slightly above the idle stop.

[SlowGoinE30]

Not so helpful eh?

If you look under the throttle body you'll see a black box with a 3 pin connector coming out of it, unplug it.

To test the TPS use a voltmeter in the continuity setting.

The two poles towards the front of the car should have continutiy at idle. ( left / Middle ) So just remove the pug, plug your tester onto those two wires and your voltmeter should be beeping.

To test the other part of the tps, hook it up to the other two wires, ( middle/ right ) on the plug. When you reach about 75% of full throttle, it should switch the WOT switch, and again, there should be continuity.

If your getting continuity at idle, but not WOT it may need to be adjusted, same as vice versa, if your not getting continuity at idle but you are at WOT it will need to be adjusted.

They do die though.

To move it you'll need to undo all the cables going to the throttle body, take off the 4 10mm nuts holding the throttle body on, and move it forward. This will give you the ability to remove/loosen the two screws for the TPS ( on on either side ) they are phillips head screws.

Try just loosening it and getting it to work before taking it all the way off because getting it back on can be a bitch.

Hope that helps you.

[Vince30]

I just got on the computer and its dark outside, but thank you for going into details, I guess this is common knowlage to most people lol. I will look at it right after work tomorrow and post back.

[SlowGoinE30]

It wasnt to me, I just had to do this because my WOT portion wasn't working.

But chances are your idle one circuit isnt clicking anymore, when I put mine back on the first time it wasnt properly adjusted, and it never activated the idle switch, and it revved at about 1300 rpm at idle.

I highly recommend a 10mm with a universal joint for getting at the lower left bolt of the throttle body if you plan on adjusting your tps.

[87e30]

Not so helpful eh?

If you look under the throttle body you'll see a black box with a 3 pin connector coming out of it, unplug it.

To test the TPS use a voltmeter in the continuity setting.

The two poles towards the front of the car should have continutiy at idle. ( left / Middle ) So just remove the pug, plug your tester onto those two wires and your voltmeter should be beeping.

To test the other part of the tps, hook it up to the other two wires, ( middle/ right ) on the plug. When you reach about 75% of full throttle, it should switch the WOT switch, and again, there should be continuity.

If your getting continuity at idle, but not WOT it may need to be adjusted, same as vice versa, if your not getting continuity at idle but you are at WOT it will need to be adjusted.

They do die though.

To move it you'll need to undo all the cables going to the throttle body, take off the 4 10mm nuts holding the throttle body on, and move it forward. This will give you the ability to remove/loosen the two screws for the TPS ( on on either side ) they are phillips head screws.

Try just loosening it and getting it to work before taking it all the way off because getting it back on can be a bitch.

Hope that helps you.

What do you mean by continuity? My voltmeter doesn't beep but I should just see a steady current?

Do test the middle/right for WOT do I need to be pushing the gas pedal down?

[87e30]

Okay... I have no idea what I'm doing. I can't even find the tps. I know I 'm a huge n00b when it comes to opening the hood.

But it appears my tps needs adjusting.

Any more in depth help would be greatly appreciated.

[Adrian_Visser]

okay an '86e has motronic 1.0 meaning that it has a separate idle control unit. Here is another way to test your tps and pretty much every other signal that the idle control unit uses. The best part is you don't even have to open the hood!

1: open your glove compartment

2: remove the two small black screws and two plastic half turn clips that hold the plastic cover in the top of the glove compartment off.

3: you will see the DME, and to the left of that a smaller green plastic box this is the idle control unit, remove the one 10mm bolt holding it in place and disconnect the electrical connector

4: on the control unit you will see 12 pins with numbers stamped into the plastic next to them, the corresponding sockets in the electrical connector is what you will be testing with your multi meter. Remember that when comparing the numbers on the ICU to the connector the connector is a mirror image.

5: with the meter set to ohms aka resistance, (continuity beep would be easier as you wouldn't have to watch the meter but w/e) push the meter leads into sockets 4 and 12 of the connector, you should have continuity i.e. close to zero ohms resistance.
The Bentley manual says that you should have battery voltage for one to two seconds with the ign. in the on pos. to check this you would have to pop open the connector (not hard to do really) and check across those terminals with it conected to the icu.

*if you own a Bentley manual there is a checkout procedure for the ICU on P28 of chapter 6

having said all this I went through the same thing with my '84 eta and didn't find a thing wrong. How old is your O2 sensor and what kind of gas mileage do you get?

The O2 sensor signal is ignored by the DME until the engine reaches a certain temperature so if your O2 was bad it could I think do this. Since I'm ressurecting that poor car from the dead for my little brother to drive and I now have a new O2 sensor to put in I will get back to you if this fixes it.

[87e30]

okay an '86e has motronic 1.0 meaning that it has a separate idle control unit. Here is another way to test your tps and pretty much every other signal that the idle control unit uses. The best part is you don't even have to open the hood!

1: open your glove compartment

2: remove the two small black screws and two plastic half turn clips that hold the plastic cover in the top of the glove compartment off.

3: you will see the DME, and to the left of that a smaller green plastic box this is the idle control unit, remove the one 10mm bolt holding it in place and disconnect the electrical connector

4: on the control unit you will see 12 pins with numbers stamped into the plastic next to them, the corresponding sockets in the electrical connector is what you will be testing with your multi meter. Remember that when comparing the numbers on the ICU to the connector the connector is a mirror image.

5: with the meter set to ohms aka resistance, (continuity beep would be easier as you wouldn't have to watch the meter but w/e) push the meter leads into sockets 4 and 12 of the connector, you should have continuity i.e. close to zero ohms resistance.
The Bentley manual says that you should have battery voltage for one to two seconds with the ign. in the on pos. to check this you would have to pop open the connector (not hard to do really) and check across those terminals with it conected to the icu.

*if you own a Bentley manual there is a checkout procedure for the ICU on P28 of chapter 6

having said all this I went through the same thing with my '84 eta and didn't find a thing wrong. How old is your O2 sensor and what kind of gas mileage do you get?

The O2 sensor signal is ignored by the DME until the engine reaches a certain temperature so if your O2 was bad it could I think do this. Since I'm ressurecting that poor car from the dead for my little brother to drive and I now have a new O2 sensor to put in I will get back to you if this fixes it.

thank you! I guess I'll try an o2 first.

I'm getting 22mpg mixed. I have no idea when the o2 was last replaced and I'm failing emissions testing so I think I'l have to pick up a new o2 sensor tomorrow...

[Adrian_Visser]

no prob what i forgot to say in that post is that when you press the gas peddle down a bit you should get infinite resistance as the idle switch of the tps will now be open.