Cold Idle

[jsloden]

Hey guys, having a real problem with the cold idle. In order for the car to idle when it's cold you have to keep your foot on the gas. If you don't it will die. This usually takes a couple of minutes. As soon as the temp needle starts to come up it's like a switch is tripped and it idles perfectly. I was leaning towards cold start valve? This was replaced within the last year though.

Thanks,
Justin

[dmcnc]

Cold start valve doesn't affect your idle while cold; It would flood your car if it stays open or a closed one would require an extended crank.
Check your Idle Speed Regulator operation by pulling the Idle ECU plug facing the center of the car. If your rev's jump significantly, then you're ISM is good. If it doesn't make a difference in RPMs, we'll keep troubleshooting from there.

[David T]

Cold start valve doesn't affect your idle while cold; It would flood your car if it stays open or a closed one would require an extended crank.
Check your Idle Speed Regulator operation by pulling the Idle ECU plug facing the center of the car. If your rev's jump significantly, then you're ISM is good. If it doesn't make a difference in RPMs, we'll keep troubleshooting from there.

During cold start-up the one thing that has the biggest effect is the Control Pressure Regulator aka warm-up regulator. It acts like the choke on a carbureated car and rich-ens the Air/Fuel ratio till the motor warms up. You test the CPR by hooking up a pressure gauge and watching it as the motor warms up to confirm proper operation of the CPR. If necessary they can be rebuilt.

[jsloden]

Ok, pulled the plug on the isr. Didn't make a difference. The car starts up easily the first time when cold. If you kill it before it warms up then you you have to give it a lot of gas to get it to restart. As soon as the needle temp needle it's like a switch is flipped and it idles perfectly. Both the isr and the warm up regulator are only a few months old. They were both replaced by dmch back in the summer. how would I check to see if they're getting voltage. Would the key have to be on, car running, etc...?

Thanks

[dmcnc]

Ok, pulled the plug on the isr. Didn't make a difference.
- just to make sure, you pulled the plug on the ECU computer - right?
55039
If you pull this plug with the car running, your idle should spike significantly (and confirms your idle speed reg is good).

The car starts up easily the first time when cold. If you kill it before it warms up then you you have to give it a lot of gas to get it to restart.

- The 12Vs from the start-up circuit (during crank) will warm up the thermotime switch (TTS) and shut the Cold Start Valve shortly after the first crank.This prevents you car from "flooding."

Both the isr and the warm up regulator are only a few months old.
- My first DMCH ISR came from a bad batch of Chinese sourced units, and failed within a few months. Should you have to replace this one, consider getting an OEM Bosch replacement or something like this - http://www.ebay.com/itm/like/152587819390?ul_noapp=true. Otherwise it should still be on 1-year warranty?

how would I check to see if they're getting voltage.


- Both plugs should get 12V with the key on run.

[jsloden]

Okay, got 12 volts at the idle control valve but nothing at the warm up regulator. Do you know which pin I could check at the computer and where I could check it at the bulkhead connectors?

Thanks

[DMC5180]

Turn the key to Run without starting and put your hand on the ISM. Does it vibrate?


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[jsloden]

Okay, turned the key to run and nothing vibrates. I was tracing the yellow/red wire that goes to the warm up regulator. It goes back through the bulkhead in the blue connector. I unplugged the blue connector and that pin is not getting any voltage. I went back to the fuse box to check the number one fuse which is the one that the warm up regulator in on. The fuse is good. I then noticed that it looks like that yellow/red wire runs through the rpm relay. Does the rpm relay turn the warm up regulator on and off? If so, this could be a problem. I checked for voltage at the rpm relay with the key on and it isn't supplying any voltage to the yellow and red wire.

[dmcnc]

With the relay plugged in, can you confirm the RPM relay is getting power (green cable) with key on Run and nothing is coming out the WUR cable pin (yellow/red). Do you have an extra RPM relay for testing?


Okay, turned the key to run and nothing vibrates. I was tracing the yellow/red wire that goes to the warm up regulator. It goes back through the bulkhead in the blue connector. I unplugged the blue connector and that pin is not getting any voltage. I went back to the fuse box to check the number one fuse which is the one that the warm up regulator in on. The fuse is good. I then noticed that it looks like that yellow/red wire runs through the rpm relay. Does the rpm relay turn the warm up regulator on and off? If so, this could be a problem. I checked for voltage at the rpm relay with the key on and it isn't supplying any voltage to the yellow and red wire.

[jsloden]

Yes, with the key on the rpm relay gets voltage, the green wire. But there is nothing at the yellow and red wire. Unfortunately I don't have another rpm relay.

[Elvis]

I bet the ISM is stuck or the ECU not working

[jsloden]

One of those could be the issue. But if the warm up regulator should be coming on with the key and it's not I would definitely like to get that solved first.

[DMC5180]

One of those could be the issue. But if the warm up regulator should be coming on with the key and it's not I would definitely like to get that solved first.

The WUR (heater element) is only live with engine running.

The ISM should run (vibrate) with key In Run.

What is your current ambient temp?

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[jsloden]

Okay, so the WUR doesn't come on unless the car is running correct? The idle motor has voltage going to it but is it definitely not buzzing or doing anything. The ambient temp is 48.

[DMC5180]

Your RPM relay is probably fine since the engine runs. Fuel pump is working.


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[DMC5180]

Okay, so the WUR doesn't come on unless the car is running correct? The idle motor has voltage going to it but is it definitely not buzzing or doing anything. The ambient temp is 48.

Correct. (The heating element) within it.

Just thought of something, make sure the idle Micro-switch is depressed when you have the key in the run position. This is the ground for the Idle ECU to operate.


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[dmcnc]

OK now. With the engine running, are you getting power at the WUR plug?

[Elvis]

I know you guys hate it when I say - I said it many times already - the idle switch does NOT turn on the ECU !

The idle ECU is always on, but pressing the switch sets the level to 775rpm, depressing it sets the speed to a higher level.
(plus drives the valve for the air)


the idle system has many known and often discussed problems
some which fit here are:

- idle motor freezes / bearings rust

- ECU power stage fails

[Bitsyncmaster]

The idle system still works without the idle switch pressed. So like Elvis said, it's probably a frozen idle motor or bad idle ECU.
If you unplug the 4 pin connector on the idle ECU the idle motor should go to full open and after a few seconds it will start to close and start buzzing (when you turn the key to on). Note: unplugging that 4 pin connector also unplugs the idle switch along with the thermistor.

Some RPM relays have separate contacts for the two outputs. So even if your fuel pump runs the second output may not be driving the WUR heater.

[DMC5180]

The idle ECU is always on, but pressing the switch sets the level to 775rpm, depressing it sets the speed to a higher level.
(plus drives the valve for the air)


the idle system has many known and often discussed problems
some which fit here are:

- idle motor freezes / bearings rust

- ECU power stage fails

How does depressing the Idle micro set the speed to a higher level?




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[jsloden]

Ok, with the car running, the WUR has voltage. With the car running it doesn't change anything when I unplug it. Again, with the car running the ISM also has voltage. It also doesn't change anything when I unplug it. Should the idle change when I unplug it?

[Bitsyncmaster]

How does depressing the Idle micro set the speed to a higher level?




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I never really found what effect the idle switch has on the idle ECU. But with the idle switch off, you get ignition advance and that will most likely overcome the capability of the idle system to hold 775 RPM.

[DMC5180]

Ok, with the car running, the WUR has voltage. With the car running it doesn't change anything when I unplug it. Again, with the car running the ISM also has voltage. It also doesn't change anything when I unplug it. Should the idle change when I unplug it?

Typically the when unplug the ISM while at idle it will stumble or die completely. Not always though it is a bit condition dependent.


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[jsloden]

Ok, just unplugged the left plug from the idle computer while the car was running. There was no change in idle.

[Bitsyncmaster]

Ok, with the car running, the WUR has voltage. With the car running it doesn't change anything when I unplug it. Again, with the car running the ISM also has voltage. It also doesn't change anything when I unplug it. Should the idle change when I unplug it?

Try unplugging the 4 pin connector on the idle ECU when the car is running. That should bump the idle up between 2000 to 3000 RPM if the idle system is working. If you get no change than something is dead in the idle system.

[jsloden]

Okay, unplugged the 4 pin connector from the computer. No change in idle. Could there be bad solder joints in the computer. I would really rather not have to buy one of those.

[Bitsyncmaster]

Okay, unplugged the 4 pin connector from the computer. No change in idle. Could there be bad solder joints in the computer. I would really rather not have to buy one of those.

Can you borrow one from another owner? Have not heard of any bad solder joints with the idle ECU (it does not get that hot and has conformal coating sprayed on the circuit board).

[DMC5180]

Okay, unplugged the 4 pin connector from the computer. No change in idle. Could there be bad solder joints in the computer. I would really rather not have to buy one of those.

I would verify your ISM is not Stuck first.

You can move (pivot) the cold start valve tube toward you about 1/2 inch. This is usually enough to slip the short connector hose off the ISM. Push the hose to the side so can shine a light into the the ISM port to see the rotating valve position.



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[jsloden]

Not too many Delorean owners in North MS unfortunately. The only other one around here is in a museum. I think they would frown on trying to take parts off of it. If the ISM is getting voltage does that rule out the computer? Because like I said earlier, with the key on run the ISM gets voltage but it doesn't buzz.

[DMC5180]

One of those could be the issue. But if the warm up regulator should be coming on with the key and it's not I would definitely like to get that solved first.

to clarify, the Warm up regulator does not get power with the key in RUN, only if engine is running. Which you already verified.

This is normal. You will not have power without the engine running because it is Fed from RPM relay operation.


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[Bitsyncmaster]

Not too many Delorean owners in North MS unfortunately. The only other one around here is in a museum. I think they would frown on trying to take parts off of it. If the ISM is getting voltage does that rule out the computer? Because like I said earlier, with the key on run the ISM gets voltage but it doesn't buzz.

I have a few OEM units I have not updated yet. I also have my updated units for sale. If you just want to test the ECU I can send you one for the price of shipping but you would need to return it or buy it.

[jsloden]

Yes, the warm up regulator on comes on when the engine is running which is what it's supposed to do I guess. It sounds to me like it's either the computer or the ISM. Thanks for the offer of letting me test one of your computers, I really appreciate it. I think what I'm going to do though is call dmch tomorrow and see if they'll do an exchange on the ISM since this one's still under warranty. If that doesn't solve the problem I will definitely take you up on your offer.

Thanks

[DMC5180]

Yes, the warm up regulator on comes on when the engine is running which is what it's supposed to do I guess. It sounds to me like it's either the computer or the ISM. Thanks for the offer of letting me test one of your computers, I really appreciate it. I think what I'm going to do though is call dmch tomorrow and see if they'll do an exchange on the ISM since this one's still under warranty. If that doesn't solve the problem I will definitely take you up on your offer.

Thanks

Under warranty? Please tell us the history of your vehicle ownership.


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[Bitsyncmaster]

Under warranty? Please tell us the history of your vehicle ownership.


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Yes history would help. If you have one of my idle ECUs, it does not buzz the ISM when the key is turned on. Mine would have a blue wire coming out between the two connectors or you could have an 11 pin unit I also sell.

The ISM wires pass through the bulk head connectors with is another possibility of failure.

[jsloden]

Ok, I might be getting some of my acronyms mixed up. The car was at delorean of Houston back in the summer for a couple of months getting a partial restoration done. Basically just getting the car into running, driving shape. This is where and when the new idle motor was installed. This was one of a few new parts that were installed to get the car running. As far as I know the computer that's in the car is the original that it came with. They did not have to change this out. I was under the impression that the parts that were put on the car had at least a one year warranty.

Thanks

[dmcnc]

It's a bad Idle Speed Motor. If you want to confirm, with the car off - unscrew it from the bracket and both hoses, hold to where you can see inside the airway facing the rear of the car. At this point put the key in and on run, you should see the ISM swing open and slowly close (over the course of 30 seconds). If it doesn't do this, it's stuck or dead. Again, these new chinese units are not very reliable (I've gone through two of them) .

Ok, just unplugged the left plug from the idle computer while the car was running. There was no change in idle.

[DMC5180]

Ok, I might be getting some of my acronyms mixed up. The car was at delorean of Houston back in the summer for a couple of months getting a partial restoration done. Basically just getting the car into running, driving shape. This is where and when the new idle motor was installed. This was one of a few new parts that were installed to get the car running. As far as I know the computer that's in the car is the original that it came with. They did not have to change this out. I was under the impression that the parts that were put on the car had at least a one year warranty.

Thanks

Okay,

New ISM’s don’t usually fail. Old one’s can suffer from Rust in the bearings or carbon build up in the valve end.

I think you should At least pull the short connector hose off the ISM that connects to the Cold Start tube. The tube will pivot towards you enough to slip the hose off the ISM. Then just push it aside so you can see in the Port with a Light. You should be able to move the valve with a blunt tool or pencil with eraser head.


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[jsloden]

It's a bad Idle Speed Motor. If you want to confirm, with the car off - unscrew it from the bracket and both hoses, hold to where you can see inside the airway facing the rear of the car. At this point put the key in and on run, you should see the ISM swing open and slowly close (over the course of 30 seconds). If it doesn't do this, it's stuck or dead. Again, these new chinese units are not very reliable (I've gone through two of them) .

Okay, I'll check this out tomorrow.

Thanks

[Bitsyncmaster]

There have been some idle ECU failures. It's mostly the transistors that drive the ISM that fail. If your ISM gets a short circuit then that will probably blow the drive transistors. I don't usually test the ECU cores I get back from a customer but I have tested some of them were bad.

There also are connections issues that could make it fail. Mostly the ISM connector but the bulk head (connectors in the ignition coil box) also get corroded.

[Elvis]

Somebody finally should write a how to - how to test the idle system - and keep it on top of the how to list.

how to perform a quick test of the idle motor can be found here many times

and Dave is 100% right, most failures of the idle ECUs are the power stage transistors.

As there is a PWM switching with ~100Hz - it can't be measured with a multimeter.



to an earlier question - which does not help now to find the problem:
depressing the idle microswitch changes that PWM, because the speed setting
changes from 775 rpm to a higher value. That's not a guess, I measured it and
have the schematic.

[DMC5180]

to an earlier question - which does not help now to find the problem:
depressing the idle microswitch changes that PWM, because the speed setting
changes from 775 rpm to a higher value. That's not a guess, I measured it and
have the schematic.

The question was more in regard to your wording.

Pressing and depressing can be interpreted as the same Action.

Using the term Releasing the switch would have been a better choice.

In your explanation, pressing the switch yields 775. Releasing the switch allows an internal value to change thus Increasing RPM.

Just making sure I interpreted what you said earlier correctly.





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[Elvis]

you are right, sorry, lost in translation.

pushing = 775rpm,
releasing = higher speed

[Rich_NYS]

What was the solution to this problem?