Borrow an idle motor?

[BladeBronson]

I've been trying to diagnose a rough/high idle ever since I bought my car in October. I took it to Fremont Foreign Auto and Edwardo fixed a vacuum leak, adjusted the screws on the throttle, and adjusted the fuel mixture. It smells like it runs a little better and the idle problems seemed better, but not great (hovering in the 900 to 1100 range). Tonight, the car has been wildly fluctuating between 900 and 2000. I cleaned out the idle motor with brake cleaner and I looked inside while my girlfriend turned the car on and saw the valve close to 90%, which I think is correct. I just wonder if there's something else up with it.

So, since these take just a couple minutes to pull off, I wondered if someone is nearby and could get together for an hour on the weekend so I can try your idle speed motor. I'm in San Leandro.

[Bitsyncmaster]

So your trying to fix an idle hunting issue? In stock form, our engine idle is fixed at 775 RPM. Does yours idle at that RPM cold, hot or is the hunting so bad you can not tell what RPM it idles at?

[BladeBronson]

Thanks for the reply, Dave. I'll take a closer look Friday and will put together a video of the idle under different conditions (because I keep forgetting the specifics). I'm not sure if it would affect the idle, but my engine is a stage 2.

[PJ Grady Inc.]

I've been trying to diagnose a rough/high idle ever since I bought my car in October. I took it to Fremont Foreign Auto and Edwardo fixed a vacuum leak, adjusted the screws on the throttle, and adjusted the fuel mixture. It smells like it runs a little better and the idle problems seemed better, but not great (hovering in the 900 to 1100 range). Tonight, the car has been wildly fluctuating between 900 and 2000. I cleaned out the idle motor with brake cleaner and I looked inside while my girlfriend turned the car on and saw the valve close to 90%, which I think is correct. I just wonder if there's something else up with it.

So, since these take just a couple minutes to pull off, I wondered if someone is nearby and could get together for an hour on the weekend so I can try your idle speed motor. I'm in San Leandro.

Your idle motor sounds like it's functioning normally. In my experience stage two engines have a rougher idle than stock probably due to the cam profiles and advanced base timing. It sounds like resetting the CO again along with further testing is in order. Also ask one of the DMCH vendors what they set the base timing at and see if your's is correct.
Rob

[Delorean Industries]

If this problem becomes worse and is not a base timing/CO adjustment concern the cams are the issue. We have consistently needed to replace stage II camshafts with excessive profile wear. If you find yourself needing valve adjustments regularly this is also the issue. Don't discount this or let the modifier of the engine tell you they haven't seen this. I've also forwarded this info to other independent vendors aware of the problem as well.

[BladeBronson]

Okay, it sounds like I ought to buy a dwell meter and a timing light and see what I can find. Thanks guys.

[BladeBronson]

I shot a video tonight of the idle problems and uploaded it here: https://www.youtube.com/watch?v=m0ZpiZ4GC0g. In the YouTube video description, I've added links to skip the video to interesting parts and noted what the conditions were. The most interesting bit is that the really high idle seems to dramatically drop when the headlights are turned off. However, there are occasions when the headlights are on and the car idles steady around 1,100.

I bought a timing light and a dwell meter today. The timing light was defective and the dwell meter read "50" when set to 4 cylinder. I didn't adjust the mixture because the workshop manual says that the car should be idling normally before making adjustments.

[Bitsyncmaster]

That bouncing tach and headlight changing does look like you have electrical problems. Have you posted what your voltages are reading at idle and higher RPM?

Did your dwell hold steady after the engine warmed up? Normally the dwell will be swinging quite a bit up and down about 20 degrees or more.

[Horsebox]

I feel for you.

I wouldn't believe your rpm gauge. I watched the whole video and throughout it sounded like your tach gauge was overstating the actual rpm. There's a ten second segment starting 20 seconds into the video where the engine sounds as if it's about to die, but tach gauge is indicating 1400 or so. Maybe it's the poor sound quality of my iPad but I could never reconcile the sound of the engine to what was shown on the tach gauge. I.e the engine always sounded lower rpm than what was indicated.

Your battery voltage indicator reads very low like it isn't being charged. When you open the throttle it rises up to what I would think is a charging voltage but maybe your ignition circuit is struggling to provide a decent spark, due to the low system voltage, hence the rough running at idle. Only way to know that is make up some long cables connected to a multimeter and connect directly to the battery. As above, I would disregard the volt gauge in the binnacle.

When you press on the gas pedal it runs miles better. My hunch is that is because when the throttle spool moves off the idlespeed switch the vacuum solenoid moves to send vacuum ignition advance to the distributor. So when you press the gas pedal and the microswitch is released suddenly the engine gets the full load of vac advance, 20 degrees, and runs much better. Suggests to me your basic ignition advance is too retarded.

No idea about at the weird breathing sound right at the end of the video. I can't tell if it's fuel in the distributor causing that or just air through the intake.

Don't worry, it'll be something(s) simple and silly, and when it purrs you'll be a happy man :-)

[BladeBronson]

I checked the voltages today. The battery is 12.12 volts with the car off, just about the same at idle and just shy of 14 at 2,000 RPM. I also checked the voltage at the alternator and it's the same as at the battery. The alternator has a SpecialTAuto sticker on it and the belt is tight.

I tested the RPM using an automotive multimeter at the coil wire. The RPM was consistent with what the binnacle tachometer displays.

Last night when I was checking the dwell, I used the automotive multimeter with the positive lead on the orange wire running to the diagnostic port and grounded to the engine. It held at 50 the whole time.

[Horsebox]

12.12V under no load is a discharged/fubared battery IMHO.

50% duty cycle (45 degrees dwell set to 4 cylinder) suggests either your o2 sensor is shot or your mixture is so far out that it doesn't know where to start to try to correct it, so it defaults to mid scale.

I'd make double sure that battery of yours is OK then I'd measure the base ignition advance.

[BladeBronson]

Hmm, okay. When I bought the car (in late October), the car failed to start the first night. I bought a new battery and haven't had any starting problems since. I've only put a few hundred miles on it since then.

What should the battery voltage read? What's the right way to ensure that the alternator is charging it?

Thanks for all the help, everyone.

[Bitsyncmaster]

I have a guess for you to try. Unplug the wide open throttles switch (WOT) and see if anything changes. You should get 45 deg dwell as the cold engine warms up. If the WOT switch is pressed you should get 55 deg. Those dwell numbers are the design values so they will not be perfect. I'm guessing your WOT switch is stuck on.

Your alternator sounds like it does not provide enough voltage at idle.

[BladeBronson]

That's interesting. It might explain why this doesn't happen all of the time, and why it seems to occur after high speeds. And maybe toggling the headlights momentarily interrupts the WOT signal? I'll test tonight!

I'll also pull the battery and alternator and take them somewhere to be tested.

[BladeBronson]

I think you guys are on the right track with the battery and alternator. My girlfriend took the battery and alternator to be tested today. The 2 month old battery was "dead" (although the car would still start) and they are only able to charge it to 50%. I don't think I'll be able to return it to Pep Boys because I refused to give them my phone number. Oops. :) Autozone isn't able to test the alternator because they need some 5 digit code to enter into their tester. I have a SpecialTAuto alternator so I don't know what to tell them. Melissa's calling around to find a more old school car shop that doesn't let the computer do all the work. :)

[Bitsyncmaster]

The largest battery draw with the stock systems is the door lock unit. That will draw about 12 ma. all the time. So if your not driving the car for a month or more, get a battery disconnect. The OEM clock draws about 6 ma. A FanZilla draws about 3 ma. If you have updated a radio with a clock it will draw a few ma. also.

Most batteries have problems when they get discharged many times.

[Rich]

I think you guys are on the right track with the battery and alternator. My girlfriend took the battery and alternator to be tested today. The 2 month old battery was "dead" (although the car would still start) and they are only able to charge it to 50%. I don't think I'll be able to return it to Pep Boys because I refused to give them my phone number. Oops. :) Autozone isn't able to test the alternator because they need some 5 digit code to enter into their tester. I have a SpecialTAuto alternator so I don't know what to tell them.

That entry above plus this earlier entry:
Hmm, okay. When I bought the car (in late October), the car failed to start the first night. I bought a new battery and haven't had any starting problems since. I've only put a few hundred miles on it since then.

both are consistent with a car that isn't charging. The new battery probably ran the car for a month or so til recently. Now you know why it needed a new batt. in Oct.?

The battery might be OK but you won't know til you are getting >13V when the car is running.

The "alternator" problem may be the charge indicator lamp/connection, not the alternator....you did not mention whether that dash lamp goes on when you turn the key to ON (engine off) - with the alternator and battery connected. A blown charge lamp or a bad charge lamp connection (socket or the binnacle circuit board) will keep the alternator from charging the battery. Have you ever seen the charge lamp go on at any time since you got the car?

And did anybody try to put an LED bulb in the charge lamp (also stops the alternator)?

http://dmctalk.org/showthread.php?8051

After you sort this out you can go with a disconnect like Dave suggests or you can upgrade to a digital door lock module to knock the parasitic/standby current way down. It has other advantages over the analog module but that's for later.

[BladeBronson]

Melissa was able to get the alternator tested today and was told that it's working. I voltage tested the battery when I got home and it was 12.3 volts (the person at Autozone told Melissa that the battery would only take a half charge). I was able to swap the battery for a new one at Pep Boys and the new one reads 12.7 volts. I reinstalled the alternator and installed the new battery and went for a drive tonight. I took the same drive that I did in the video that I posted and the car behaved wonderfully. It idled perfectly around 775/800 at every stop. I was sure to floor it on the highway to trip the WOT microswitch. I'll keep an eye on it, but for now, the car is running great.

The PO added DMC's white digital door lock module and when I turn the key on, the battery light is illuminated. I remember the PO saying that he installed LED lights in the binnacle. But, when comparing the red oil, battery, and brake lights, the brightness of the battery light is different. Maybe it's wishful thinking, but I suspect that it's still an incandescent light.

Now that I know that the alternator works on a bench, the battery is new, and the binnacle light is very likely incandescent, is there a way to verify that the alternator is in fact charging the battery?

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[Bitsyncmaster]

Now that I know that the alternator works on a bench, the battery is new, and the binnacle light is very likely incandescent, is there a way to verify that the alternator is in fact charging the battery?

38775

Yes. Just need to verify your battery voltage goes to a typical 14 to 14.5 volts with the engine running. The best test of the alternator is to get the cooling fans, headlights and blower on full speed all running and verify your battery voltage is above 13 volts at idle. A weak alternator will have problems running all those loads at 775 RPM idle speed.

You can use the dash gauge but it tends to read lower than what your really have for voltage on the battery. It's better to use a volt meter at least one time to show you what your dash gauge is reading with or without the alternator working.

[Rich]

Dave's right about the charging test.

If you haven't found it as a new owner a handy place to get a decent system voltage reading is between the remote jump post (+) on rt side of engine bay and any metal bit on the engine. You probably found that jump post as you dealt with a flat battery already.
Let us know what voltage you get there with the engine on both with full load and no load (lights, fans off).

[BladeBronson]

It looks like I'm not out of the woods yet. :(

When the car is completely turned off, the voltage is 12.52 (I measured the new battery last night as 12.7 at Pep Boys) At idle, it dipped to 12.4 and when I held the throttle spool, it came up to 13.9. I then turned on the headlight high beams and ran max AC on 4. At idle, the voltage was 11.8 and with the throttle, 13.5. Every time the AC compressor clicked, it dropped to 12.9 volts or so.

Because the voltage increases with RPM, wouldn't this mean that the alternator's doing something? Could this be a case of the alternator kind of works, but isn't putting out as many amps as it once did? It has a SpecialTAuto sticker on it, but I can't discern whether it's supposed to be a 120 amp or 140 amp alternator. When Melissa took the alternator to be tested, the guy only replied that it works - he didn't give her a printout that describes the amperage rating (I'm not sure if that's common practice or not).

[Bitsyncmaster]

It looks like I'm not out of the woods yet. :(

When the car is completely turned off, the voltage is 12.52 (I measured the new battery last night as 12.7 at Pep Boys) At idle, it dipped to 12.4 and when I held the throttle spool, it came up to 13.9. I then turned on the headlight high beams and ran max AC on 4. At idle, the voltage was 11.8 and with the throttle, 13.5. Every time the AC compressor clicked, it dropped to 12.9 volts or so.

Because the voltage increases with RPM, wouldn't this mean that the alternator's doing something? Could this be a case of the alternator kind of works, but isn't putting out as many amps as it once did? It has a SpecialTAuto sticker on it, but I can't discern whether it's supposed to be a 120 amp or 140 amp alternator. When Melissa took the alternator to be tested, the guy only replied that it works - he didn't give her a printout that describes the amperage rating (I'm not sure if that's common practice or not).

Yes the alternator is working but has low output at idle speed. I had an older Specal T alternator (I think it was a 110 amp) that worked fine on my car at idle speed. I now have a DMC 130 amp that also works fine at idle speed.

[BladeBronson]

I received my new alternator from DMC Houston tonight. On the website, it was listed as a 120 amp alternator, but it came with a little card that rated its output at 59 amps @ 2400 RPM and 147 amps @ 7500 RPM. I was a little concerned that it might not improve my voltage at idle.

I took readings again with the old alternator first:
12.55 with the engine off
12.25 at idle, just after starting.

I didn't let the car heat up or take it for a drive because I was going to swap the alternator immediately. After the swap, my voltages are:
12.6 with the engine off
14.6 at idle, just after starting!!!

I haven't run into the 2,000 RPM at idle problem ever since I swapped out the battery with a fully charged one last week.

Guys, thank you so much for the help on this. I really thought that this was a byproduct of a problem with the fuel mixture or the idle motor. The volt meter was right there in front of me the whole time, but I didn't know what was out of the ordinary so I didn't notice it. I think this problem might be solved.

[BladeBronson]

Aaaaand just now I found the alternator dyno report in the bottom of the box. The RPMs stated in my last post are alternator RPMs, which should be 3x greater than engine RPM. Here's the sheet for anyone that's interested.

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