erratic idle w/ window switches

[Fox2506]

When idling, if I depress both window switches 'up' simultaneously (windows already up), my engine revs to 2K in a sputtery unsmooth fashion. It works every time, but I try not to do it. I do have PO installed aftermarket window regulators of unknown brand.

Also, I later discovered that after a hard drive or long highway cruise, I'll come to a stop and experience the same revs. Usually one or two unhealthy sounding revs.

My guess is that pressing both switches somehow opens the idle motor a bit. This is totally unlike rev hunting (which is usually smooth). I have video if anyone wants to see.

[hmcelraft]

You didn't mention if the clock resets or any other ghosts. But, I would suggest you check the grounds from the idle speed control unit - all the way from the control unit to the battery ground. I believe the ground from the controller ties into a gang connection that includes the window switches (the motors operate by switching the direction of + through the motor to a ground in the window switch). The ultimate ground to the battery inside the car ends up at the ground post behind the back panel of the rear package shelf on the passenger side. The ground from the battery is via the frame connection in the engine compartment. That should be checked too. I have found the compression of the fastener behind the panel can loosen and the ground strap to the frame can become contaminated. Also, the ground on the metal tray holding the idle speed controller can loosen.

Harold McElraft - 3354

[Fox2506]

I don't think the clock reset. Then again I never look at it.

I want to say somethings wrong with the ECU. The car has had a frame and engine restoration, but has retained some quirks like an odd emission smell. I'll check there first, but has anyone heard of such a thing being caused by a bad ECU?

[Bitsyncmaster]

Can't say I have ever done that (press both windows up at stalled position). Your probably drawing 20 amps or more so your voltage may be dipping or as suggested a poor ground most anywhere can do those weird things.

[Ron]

Can't say I have ever done that (press both windows up at stalled position). Your probably drawing 20 amps or more so your voltage may be dipping or as suggested a poor ground most anywhere can do those weird things.
+1

Put a volt meter directly on the battery or maybe the feed to the ecu feed(s) (don't trust the one in the dash)..I bet you see an obvious drop down to or below 12V, which will screw up the ecu(s).

[David T]

It does sound like when your system voltage drops the idle motor loses control authority. You might want to watch the voltage on the idle ECU when the motor speeds up. And check for a voltage drop across the ground connection. It is not good to force the window motor against the up or down stop. You can damage the window switches, they carry the full motor current, there are no relays. You can also damage the window regulators and knock the window off the track. There should be no "odd smell" once the motor warms up. If there is, the motor is not running right. Another big indicator is gas mileage. It should be over 20 MPG. With a 5-speed it can be as high as 25 MPG.

[Fox2506]

I understand it's not good to force the windows, I didn't do it excessively. As it turns out though, this occurs any time i depress a switch in either direction open or closed.

Also, the issue seems more prevalent tonight. It's getting worse.

I'll try these tips, but I dont understand why this would be a ground issue if the grounds have been vastly improved with the frame resto (grounds being one of the main concerns). Perhaps there's a body ground.


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[Bitsyncmaster]

I understand it's not good to force the windows, I didn't do it excessively. As it turns out though, this occurs any time i depress a switch in either direction open or closed.

Also, the issue seems more prevalent tonight. It's getting worse.

I'll try these tips, but I dont understand why this would be a ground issue if the grounds have been vastly improved with the frame resto (grounds being one of the main concerns). Perhaps there's a body ground.


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Most all the circuits share a ground connection in the back of the relay compartment. So if you add a 20 amp load and that ground is marginal, you may see that shared ground go to 1 or 2 volts where as a good ground it should read almost zero volts. Your idle ECU also uses that ground.

[Fox2506]

I haven't found any bad grounds yet--all clean and tight. Checking the one behind the passenger side bulkhead next.

The window switch revs only occur when the engine is hot, which I have just realized.

[Fox2506]

Finally pulled off the rear bulkhead cover.

The grounds are clean and tight, but the brown wire junction to the jump post is just loose enough to twist the eyelets around.

In the wiring diagram, I see grounds coming off of the window switches. Where do they wind up?

I'm stumped, as I already had the feeling that I wouldn't find any suspicious grounds.

[Jonathan]

Just to clarify, the grounds are normally BLACK wires, oui? And the BROWN wires are normally carrying 12 volts somewhere, si?

[Rich]

...In the wiring diagram, I see grounds coming off of the window switches. Where do they wind up?

Middle of center section of frame beneath console.

You will find info about those and other ground locations in this handy Resources posting:

LINK: http://dmctalk.org/showthread.php?1301-Ground-Location-List (http://dmctalk.org/showthread.php?1301-Ground-Location-List&highlight=list+grounds)

[Rich]

Just to clarify, the grounds are normally BLACK wires, oui? And the BROWN wires are normally carrying 12 volts somewhere, si?

Si.

Look for most of them radiating from junction in quadrant B6/C6 here:

LINK: http://dmctalk.org/showthread.php?17-DMC-12-color-wiring-diagram (http://dmctalk.org/showthread.php?17-DMC-12-color-wiring-diagram)

[Fox2506]

Awesome. I'll bet that's the one.

[Fox2506]

Middle of center section of frame beneath console.

You will find info about those and other ground locations in this handy Resources posting:

LINK: http://dmctalk.org/showthread.php?1301-Ground-Location-List (http://dmctalk.org/showthread.php?1301-Ground-Location-List&highlight=list+grounds)

I've finally taken out the console today, after addressing the headliner leak issue.

All I found was that the radio bracket ground was a bit loose, and my left window switch connector is slightly melted (past issue that hasn't recurred).

I see the window switch ground goes to the bulkhead, which looks good. I have the incandescent illuminated switches with the jumpers installed. I'm thinking since the issue happens when the car is warmed up, it's happening when that connector or switch is heating up/shorting out. Perhaps I should try replacing the worn window switch connectors. Are they available? I also believe my switches are messed up. The light is finicky and I sometimes have to tap them to make them work. They do get hot.

[Exolis]

Measure the voltage between GND of the Idle Speed ECU and Battery GND. If it's above 1V while you have both window switches up, you have Grounding Issue.

[Fox2506]

Thanks, I'll start measuring things when it finally stops raining.

I definitely need to replace my window switch connectors. With the console out, I played around with the switches while the car idled a bit. Agitating the wires seemed to slightly change the idle (not just the tachometer), probably because the dividers between the wire inlets are all broken. I couldn't replicate the surge upon pressing the switches, but the car hadn't been running long enough anyway. Also, the driver side switch (originally) does not work on the passenger side connector..:hmm: At the very least I'm going to have to cut off the connectors and crimp on some insulated female tabs.

Additionally, my volt gauge read right at 8 upon starting the car. One rev quickly kicked it up to the next mark where it stayed. My alternator is a cross-referenced part from Napa, that's been working for about 3 years.

++Just remembered--Josh told me my somewhat new Interstate battery was shot. Dead cell I think.

[Bitsyncmaster]

The window switch terminals are a size smaller than the standard 1/4". I don't think you will find insulated terminals local.

[Fox2506]

I measured them at about .180 - .193", which are real terminal sizes. So yeah they are smaller. Anyone know of a product that fits?

[Tillsy]

In the metric world there are a wide variety of connectors that vary by the mm - so easy as pie to get the right size.

You don't have that availability in imperial - just set sizes such as 1/4"?

[Fox2506]

Auto parts store had em. 3/16" Female disconnect terminals. Part #85446

[Bitsyncmaster]

Auto parts store had em. 3/16" Female disconnect terminals. Part #85446

I looked all over in my area and could only get 1/4" or 1/8". Glad you found them.

[Fox2506]

So, I removed the melted connectors and left the old terminals since they were fine. I put shrink tubing around the terminals. I meticulously hooked up the correct leads to the switches and found that my switches are faulty. One switch only works one way and the other's light only works when pushing on it. I'll take them apart to diagnose this.

If I get new illuminated switches, will they be the same, or have there been improvements (bought mine in 2010). Does anyone recommend the LED version? **Just looked--so they upgraded and sell the LED version only. But is it durable?

Anyway, I'm confident this is a step in the right direction to resolving the original issue. Those connectors were toast.

[Bitsyncmaster]

If I get new illuminated switches, will they be the same, or have there been improvements (bought mine in 2010). Does anyone recommend the LED version? **Just looked--so they upgraded and sell the LED version only. But is it durable?

The LEDs are soldered into the switches. The bulbs wrapped wire around a plastic part that tends to break and loose connection.

[Fox2506]

The LEDs are soldered into the switches. The bulbs wrapped wire around a plastic part that tends to break and loose connection.

I know what you mean about the bulbs. Thanks, sounds like an upgrade.

[Fox2506]

Ok, I finally cleaned out my tools and made the car drivable so I could make a video of the issue. I drove around for about 15 minutes and got it hot. On the way home the idle was just gone. When I downshifted and let off the gas, it even felt like the car was still trying to go.

Here's the video from when I got home (had trouble getting a good angle): http://www.youtube.com/watch?edit=vd&v=KNlwY7h4JUs

Remember, this does not occur when cold or warm; just hot. This video also doesn't display the window switch causing a surge in this occurrence because the system was stuck in the surge mode. Sometimes the idle unexpectedly goes back down, then the switch just happens to trip the constant surge again.

I am going back out to check voltages and such.

[Jonathan]

One way to try and sort this out would be to think of or list any components or systems that COULD be making this happen.

Ruling out a very coincidental chance of the idle jumping up when you do the window switch thing and it STILL being mechanical related, I'd rule out the throttle spool or cable for the moment. Like you said, it doesn't seem mechanical and when you are pressing the idle microswitch with your finger, it doesn't make it settle back down. Similar to how snapping the gas with your foot wasn't helping.

So, what parts of the car contribute to your idle (in general)?

(and this is not an area I would consider myself an expert so others might need to chime in.)

- If the engine is revving high and it is not related to the throttle spool movement, perhaps there is a incorrect connection on one of the components in the system that regulates the idle? Electrical likely, but maybe vacuum too. Perhaps you could trace out these electrical connectors in the engine bay or behind the seats and ensure each is clean, a good connection, AND it is going to the correct component?

Just talking out loud more than anything, but ya, if it is related to the window switch, there is something hiding that is doing this. Did you trace back the window switch wiring to it's source and confirm all is as it should be? The two things obviously should not have an effect on each other, so it might be something as obvious (or not obvious) like a wiring connection got terminated in the wrong place.

- Maybe have a look at the connections on the idle speed microswitch and compare them to the schematics. Who knows, maybe something got crossed up there and what is supposed to make it settle down is actually causing it to jump up. I don't think manual trans cars have the kickdown microswitch, but I could be wrong. What made me think that was if this was an auto, it's almost like those two things got switched around.

[Fox2506]

Good analysis. Also keep in mind that the car worked fine for a month. Then I just happened to notice the window switch issue by chance so who knows how long that went on. Then after a 3 hour drive the idle began the erratic nature. Today it was MUCH worse.

My guess is still that something got hot and when heats up, shorts out.

Battery checks out at 12.5v off and 14.5v engine on. Although the dash readout is +-10v but whatever.


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[Jonathan]

Good analysis. Also keep in mind that the car worked fine for a month. Then I just happened to notice the window switch issue by chance so who knows how long that went on. Then after a 3 hour drive the idle began the erratic nature. Today it was MUCH worse.

If we keep it in that "simple stuff first" methodology, lets focus on the car worked fine for a month part.

Are you a new owner and just got the car, and this particular month was the first month of your ownership? Or did it not work fine for a while and then it had a good month?

With that in mind, can you share what changed from the time you last recall it working fine and now? Or when you noticed it not working fine? If it wasn't noticed earlier, that's ok too, but lets see if any recent work or happenings might lead us to the problem.

New upgrade projects? Console out for some reason like a stereo install? You look to have some pretty nice and new looking engine components in your video, when did those go in? Before or after you noticed the problems? Noteably the three brass screws right near the idel speed microswitch and what not look like they are freshly back from a plating place. Perhaps something got out of order when parts got put back together?

[Fox2506]

Owner 10yrs. Just had a frame resto and engine overhaul.

Anyway to update. Started warm: fine. Drove got it to act up again and started unplugging fuses: no change. Volt meter read 13.5 whole time.

Turned off then 30 sec later turn on and starter did not engage. Waited a bit, then started fine, idled fine for 10 sec then instantly jumped to 2k and stayed there. Perfect 2k idle no bumps or sputters. It was impressive really. Just not right. Just FYI

From my phone.


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[Tillsy]

Try turning the key to run, but don't actually start her. Leave it that way for 20 minutes or however long until you are sure it would normally begin to malfunction 'hot'. Then start her and see if she quickly pegs up to 2k.

Will help narrow if the heating issue is electrical or mechanical.

If it turns out to be electrical I'd pop the idle ecu circuit board out of its black box whilst the issue is occurring, spray some electrical freeze on it, and see if the issue instantly vanishes.

[Exolis]

Good analysis. Also keep in mind that the car worked fine for a month. Then I just happened to notice the window switch issue by chance so who knows how long that went on. Then after a 3 hour drive the idle began the erratic nature. Today it was MUCH worse.

My guess is still that something got hot and when heats up, shorts out.

Battery checks out at 12.5v off and 14.5v engine on. Although the dash readout is +-10v but whatever.


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Did you try measuring the voltage at Idle ECU Ground to the Battery Ground? (When the problem is occurring).

[Fox2506]

It reads 0.42 V.

I unplugged the ecu plugs to check resistances. The idle went permanently to 2k and even plugging them back in doesnt stop it. Turn car off and on twice, no change. Bad ecu? I'm going to try a swap with a local owner if I can later.

I checked my mixture too at 45 and 52 when full throt switch is depressed. Odd because it doesn't run or smell as well as it reads.


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[Fox2506]

Swapped ECU with local owner. Seems to be fixed.

Window switch thing isn't happening either. Gona run it for a few days and see what happens. Just hope my ecu died of old age and that there's no culprit.


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[Tillsy]

Just hope my ecu died of old age and that there's no culprit.

That was my suspicion in the post above, the circuit is overheating due to age - lots of factors that can cause that.

Replace it with bitsyncmaster's microprocessor controlled one - eliminates the fiddly idle switch and drastically cuts power when engine not running.

[Fox2506]

ECU comparison, just to show.
http://www.youtube.com/watch?edit=vd&v=XE0A1CP5gJk

[Elvis]

Thanks for the video, now this really is a cool effect :-)

What I could imagine is that some capacitors inside the ECU are dried out and let noise on the supply line thru.
or
due to vibrations a solder connection is loose.


If you want to spend some bucks for shipping, I'd like to repair it for you for free, just out of curiosity what
the problem is.

Elvis & 6548

[Fox2506]

Plugged in new O2 sensor today. No change in the richness issue. Cannot get the mixture off of 45 when at operating temperature. Running some more tests atm.

Checked connections, blue wire, Lambda computer and grounds. Nothing looks out of place/melted/corroded.

Thankfully, the idle ECU swap is still working.