Yet another 528e surging idle thread

[tig]

I've read every thread I could find on this subject. None of them really help.

1987 528eA - 202k miles

Video showing the problem:
http://youtu.be/ZEUdcqa1-bs

What I've tried:
- Swapped thermotime switch (it was easy)
- Pulled ICV and cleaned it thoroughly. Did not test it.
- Sprayed carb cleaner everywhere looking for vacuum leaks. No change in idle.

Any other suggestions?

[wkohler]

When it's doing it, hit the green box in the glovebox above the ECU. That's the idle control module. Definitely sounds like the valve is working. It just doesn't know what to do.

[tig]

When it's doing it, hit the green box in the glovebox above the ECU. That's the idle control module. Definitely sounds like the valve is working. It just doesn't know what to do.

According to Bentley cars made after March 86 don't have a separate ICM. Or did I read that wrong and is it after March 87 (Motronic 1.3 in the super Eta)?

[pldlnr]

3/87 is the beginning of the super eta. It used Motronic 1.1. 1.1 and 1.3 are physically the same.

[tig]

When I pull the connector of the idle control module in the glove box the frequency of the surging increases (but the amplitude stays about the same).

Whacking the module (kinda hard to do with it stuffed up there) had no effect.

[Road Trip]

Make sure the wiring to the ICV is solid. I also found that putting WD40 in the ICV helps, but just spraying it in doesn't do much. I found that operating the ICV repeatedly after oiling it while the car is running fixes whatever is gumming it up. I usually pull the connector off the ICV and temporarily make contact with the harness. You can hear it clicking.
Works for me. Still using the same valve after eight years. I've only had to do this twice.

[demetk]

I added a manual air valve before the ICV and limited the high idle to 900. The surging disappeared.

[Nebraska_e28]

When I pull the connector of the idle control module in the glove box the frequency of the surging increases (but the amplitude stays about the same).

Whacking the module (kinda hard to do with it stuffed up there) had no effect.

I had that issue here before. Pretend you're slapping a bitch that just stole your money. This will give the appropriate ft-lbs of slappage. Or swap the green box.

[Area 52]

I picked up 3 newer-looking ICVs at the local pick-ur-part for $5 each. Two out of the 3 worked...resolved the surging. Cleaning the one that was in the car and the bad replacement didn't help at all. They're a PITA.

[GKLCPA]

I battled with this last year and found that my problem was a loose O2 sensor after going through a couple of ICM's and ICV's.

[tn535i]

That surging is the classic idle control system failure. Either the control box (ICM) or valve (ICV) is probably dead. The fact that it surges indicates the throttle position TPS switch is telling it to control idle but it can't and it revs up to the fuel cutout at 1500 rpm.

Not likely that it's a big vacuum leak but maybe just the right leak. Try closing the bypass screw on the ICV all the way to see if it changes at all. If it does then maybe there is a leak somewhere.

Next unplug the 2 wire valve on any eta (non super) and it will do that unless someone has added restriction to the idle bypass hose(or an extra valve). Apply 12v directly to the two terminals on the valve and see if it clicks and moves(and slows the idle down). If it does it's probably good and the problem is the ICM. Based on your description my guess is the ICM is not able to deliver the current it needs to close the valve down. There is a setting for that current if everything is working. 475-480 mA I think. If you get a little current but can't get there it usually indicates a bad ICM.

[tig]

That surging is the classic idle control system failure. Either the control box (ICM) or valve (ICV) is probably dead. The fact that it surges indicates the throttle position TPS switch is telling it to control idle but it can't and it revs up to the fuel cutout at 1500 rpm.

Not likely that it's a big vacuum leak but maybe just the right leak. Try closing the bypass screw on the ICV all the way to see if it changes at all. If it does then maybe there is a leak somewhere.

Next unplug the 2 wire valve on any eta (non super) and it will do that unless someone has added restriction to the idle bypass hose(or an extra valve). Apply 12v directly to the two terminals on the valve and see if it clicks and moves(and slows the idle down). If it does it's probably good and the problem is the ICM. Based on your description my guess is the ICM is not able to deliver the current it needs to close the valve down. There is a setting for that current if everything is working. 475-480 mA I think. If you get a little current but can't get there it usually indicates a bad ICM.

I tried closing the screw on the ICV (I thought it was the idle baseline, not 'bypass') and near where the screw bottoms out the idle goes solid at the high (~2000) RPM. I'm planning on R&Ring all the vacuum hoses and putting on a new boot.

After cleaning the ICV I didn't test it, but I will.

[tn535i]

Do the vac hose R&R then see if that makes any difference.

In the meantime try unplugging the TPS and see what it does. It might go even higher since it will turn of the idle control and the idle fuel cut. On the other hand it might settle down to something. If not you can pinch or restrict the idle bypass hose to bring it down so that you can better perform some of the tests for vacuum leaks. That might help troubleshoot anyway potential other problems.

After you've done some of that you really need to look at ICV current to know what's going on. Keep asking questions if you're puzzled.