Idle speed suddenly high

[mluder]

Last night I was installing a new power antenna and while behind the driver seat I decided to clean things up a bit.

I unscrewed the Idle ECU from the panel and pulled the wire harnesses off it and the ECU Lambda. I sprayed contact cleaner in both the plugs and the sockets. Let them air dry while I finished the antenna.

When I hooked eveyrthing back up the antenna worked but the battery was dead so I jhump started off my wifes car. Once the DeLorean fired up, the idle speed was way high - around 2200 rpms. It's usually a hard start and bounces between 800 and 1000. Now each time I start it, it starts much easier but the idle rockets up to 2200. If I rev the engine it drops back down to about 1500 when I let up but quickly pops bac up to 2200.

Not sure what to do... Anybody have any ideas.

Steve
#4456

[Bitsyncmaster]

You probably have a bad connection on the idle ECU. Check those two connectors again and also check the diode in the harness near those connectors for good connection.

[Renee_1632]

This happened to me a few weeks ago. In my case both my idle speed regulator and ECU had gone bad. It happened suddenly to 1632 as well

[Bitsyncmaster]

This happened to me a few weeks ago. In my case both my idle speed regulator and ECU had gone bad. It happened suddenly to 1632 as well

The ECU has been known to fail. I fixed one with a bad output transistor and Elvis has fixed a few. It's not soldering problems but component failures with the idle ECU. If you were to short circuit the idle motor center terminal to one of the side idle motor terminals that would blow the output transistor.

[David T]

Try reseating the plugs on the idle ECU.
David Teitelbaum

[DMCMW Dave]

I've see a couple of bad idle motors kill the ECU. Probably for the reason Dave M mentioned.

[outatym2001]

Strange that this should come up when I was about to post my 3,000 rpm high idle problem I had on Saturday, June 18th.
Saturday morning on my way to an interview my D engine rockets up to 3,000 rpm for no reason and won’t slow down. I reach my destination and in the parking lot I look at the engine and nothing is out of place so I shut it down and go the interview.
Interviews over and I go back to the D and start it up and immediately it’s back to 3,000 rpm. I drive to a gas station and call my family I was supposed to go visit with and instead I go to DMC Northwest to a Pacific Northwest DeLorean Club tech session that started at 10 am that morning.
After much diagnosing and cleaning of the Idle/Low Speed Motor part number 102502 nothing changed.
The Idle/Low Speed Motor I cleaned two weeks earlier with brake clean but didn’t spray any lubricant inside of it.
Next we pulled a unused Idl Speed E.C.U. part 106896 off of the shelf and plugged it in. There was no change.
We installed a new Idle/Low Speed Motor and no change. We were all stumped.
Lastly we pulled one more Idle Speed E.C.U. from the shelf and plugged it in and the idle was back to being perfect.
The sudden rapid high idle problem was solved by installing a NOS Idle Speed E.C.U and at $275.00 I was like OUCH! The good thing was there was no charge for labor since we did this during a PNDC club tech session.
I also went ahead and installed a new Idle/Low Speed Motor since mine was acting like the mechanism inside was not rotating properly even after cleaning with brake clean and spraying WD40 inside of it. Idle/Low Speed Motor is $295.00 so those two parts together was an expensive day for me when I didn’t plan for it.

[Chris Burns]

Where is the ECU located?

[Bitsyncmaster]

Where is the ECU located?

Remove the board on the rear shelf behind drivers seat. The black box you see under that board is the idle ECU. Two electrical connectors attached to it.

[mluder]

Strange that this should come up when I was about to post my 3,000 rpm high idle problem I had on Saturday, June 18th.
Saturday morning on my way to an interview my D engine rockets up to 3,000 rpm for no reason and won’t slow down. I reach my destination and in the parking lot I look at the engine and nothing is out of place so I shut it down and go the interview.
Interviews over and I go back to the D and start it up and immediately it’s back to 3,000 rpm. I drive to a gas station and call my family I was supposed to go visit with and instead I go to DMC Northwest to a Pacific Northwest DeLorean Club tech session that started at 10 am that morning.
After much diagnosing and cleaning of the Idle/Low Speed Motor part number 102502 nothing changed.
The Idle/Low Speed Motor I cleaned two weeks earlier with brake clean but didn’t spray any lubricant inside of it.
Next we pulled a unused Idl Speed E.C.U. part 106896 off of the shelf and plugged it in. There was no change.
We installed a new Idle/Low Speed Motor and no change. We were all stumped.
Lastly we pulled one more Idle Speed E.C.U. from the shelf and plugged it in and the idle was back to being perfect.
The sudden rapid high idle problem was solved by installing a NOS Idle Speed E.C.U and at $275.00 I was like OUCH! The good thing was there was no charge for labor since we did this during a PNDC club tech session.
I also went ahead and installed a new Idle/Low Speed Motor since mine was acting like the mechanism inside was not rotating properly even after cleaning with brake clean and spraying WD40 inside of it. Idle/Low Speed Motor is $295.00 so those two parts together was an expensive day for me when I didn’t plan for it.

Yep... Toby related your story to me just the other day when I e-mailed him about my situation.

It turns out I had knocked loose the diode on one of the ECU harnesses. I was lucky I guess because I thought I was looking at $275 too.

Sorry, your fix wasn't less expensive.

[mluder]

Strange that this should come up when I was about to post my 3,000 rpm high idle problem I had on Saturday, June 18th.
Saturday morning on my way to an interview my D engine rockets up to 3,000 rpm for no reason and won’t slow down. I reach my destination and in the parking lot I look at the engine and nothing is out of place so I shut it down and go the interview.
Interviews over and I go back to the D and start it up and immediately it’s back to 3,000 rpm. I drive to a gas station and call my family I was supposed to go visit with and instead I go to DMC Northwest to a Pacific Northwest DeLorean Club tech session that started at 10 am that morning.
After much diagnosing and cleaning of the Idle/Low Speed Motor part number 102502 nothing changed.
The Idle/Low Speed Motor I cleaned two weeks earlier with brake clean but didn’t spray any lubricant inside of it.
Next we pulled a unused Idl Speed E.C.U. part 106896 off of the shelf and plugged it in. There was no change.
We installed a new Idle/Low Speed Motor and no change. We were all stumped.
Lastly we pulled one more Idle Speed E.C.U. from the shelf and plugged it in and the idle was back to being perfect.
The sudden rapid high idle problem was solved by installing a NOS Idle Speed E.C.U and at $275.00 I was like OUCH! The good thing was there was no charge for labor since we did this during a PNDC club tech session.
I also went ahead and installed a new Idle/Low Speed Motor since mine was acting like the mechanism inside was not rotating properly even after cleaning with brake clean and spraying WD40 inside of it. Idle/Low Speed Motor is $295.00 so those two parts together was an expensive day for me when I didn’t plan for it.

BTW... Toby mentioned I sould clean the Idle/Low Speed Motor. Is this a difficult proceedure?

[Bitsyncmaster]

BTW... Toby mentioned I sould clean the Idle/Low Speed Motor. Is this a difficult proceedure?

Solvent first then oil it up.

There are no brushes used on the motor. They use copper flex strips to connect to the armature so no worry about getting excess oil into the unit. Heck, you could submerse the thing in a gallon of oil as long as you let it drain out. I use the thin "3 in 1" oil for mine.

[outatym2001]

No not difficult. I like using nitrile disposable rubber gloves when working with solvent.
Please see page 2/5/0 of the Parts Manual. The Idle/Low Speed Motor is held in place by two socket cap screws item 14 and two rubber hoses. Loosen hose clamp behind the Idle Motor and try not to disturb the this hose too much since it’s connected to a Auxiliary Air pipe item 21. And disconnect the black electric plug.

Spray solvent through the opening and watch as black stuff comes out the other end. Keep spraying until clear. I also used cotton swabs and paper towels but DO NOT use sharp metal objects. You do not want to damage the mechanism that rotates 90 degrees. And oil it up like Bitsyncmaster says.
You can hold the Idle Motor in one hand and rotate quickly to listen for the internal mechanism. It should move freely. Mine did not even after cleaning and lubricating. So I bough a new one at $$$295.00$$$ and gave Toby P. my old one for the core charge.

[mluder]

No not difficult. I like using nitrile disposable rubber gloves when working with solvent.
Please see page 2/5/0 of the Parts Manual. The Idle/Low Speed Motor is held in place by two socket cap screws item 14 and two rubber hoses. Loosen hose clamp behind the Idle Motor and try not to disturb the this hose too much since it’s connected to a Auxiliary Air pipe item 21. And disconnect the black electric plug.

Spray solvent through the opening and watch as black stuff comes out the other end. Keep spraying until clear. I also used cotton swabs and paper towels but DO NOT use sharp metal objects. You do not want to damage the mechanism that rotates 90 degrees. And oil it up like Bitsyncmaster says.
You can hold the Idle Motor in one hand and rotate quickly to listen for the internal mechanism. It should move freely. Mine did not even after cleaning and lubricating. So I bough a new one at $$$295.00$$$ and gave Toby P. my old one for the core charge.

So, do I just use brake cleaner for the "solvent" and I think Toby mentioned WD-40.

[Bitsyncmaster]

So, do I just use brake cleaner for the "solvent" and I think Toby mentioned WD-40.

Most anything will work. You can try paint thinner. I use a solvent made to remove flux from PC boards.