setting idle

[Some guy]

Hi all

So i can finally move on to fixing the rest of my idle issues. I just replaced my WUR and i am close to getting this idle right.

When the car is hot and running the idle is set and works fine at 750 rpms. But on cold starts it hovers around 500 rpms and is close to stalling. I think i am just not setting the idle correctly to allow the idle cpu/circuit to take over.

Dose any one know the right way to set idle? or is there something i am missing? it only takes the slightest pressure on the plate to make idle correct during warm-up.


Thank you

[DeLorean03]

it only takes the slightest pressure on the plate to make idle correct during warm-up.


Thank you

Could you clarify a bit with "the plate" ?

[Bitsyncmaster]

Is your idle system working? Does the idle stay at 775 with the AC on, or headlights on....etc.

The idle speed is not adjustable in the stock system. What have you been doing to adjust it?

[Nicholas R]

Hi all

So i can finally move on to fixing the rest of my idle issues. I just replaced my WUR and i am close to getting this idle right.

When the car is hot and running the idle is set and works fine at 750 rpms. But on cold starts it hovers around 500 rpms and is close to stalling. I think i am just not setting the idle correctly to allow the idle cpu/circuit to take over.

Dose any one know the right way to set idle? or is there something i am missing? it only takes the slightest pressure on the plate to make idle correct during warm-up.


Thank you

If pushing on the plate increases you're rpms then it sounds like you're running lean and need to adjust the mixture. Pushing on the plate will push the plunger inside the distributor up, increasing the fuel flow, richening the mixture. Try turning the mixture a little bit to the right (but always remember the starting point).

[Ron]

If you warm the engine up THEN do all of the checks/adjustments, doing the CO adjustment last, the Idle Speed Motor will take care of it.

[Some guy]

I have not done anything to adjust the idle system, The only adjustments i have made is to the idle screw and switch screw. I tried to adjust the mixture screw with the allen key once, but i set it back to where it was.

Dose this sound like the right order
warm up engine
adjust mixture screw to richen the mixture,
adjust idle back down
set screw for idle switch

(doing the CO adjustment last)
What do you mean by CO?


I don't know if the idle system is working. i thought it was. The head lights have no effect on the idle speed, but the ac will drop it down 100 to 150 rpms. When i turn the ac off, the idle jumps then goes back to normal

[Ron]

FYI, It's not really an "idle screw" but an "idle stop screw", it's preset and should not be tampered with. (It is only for the throttle plates...holds them barely open.)

Adjust CO = Adjust mixture screw. (Always the last thing you do to the engine.)
Warm the engine fully.
Set timing: 13° ± 2° at 775 RPM.
Set CO: 35°-45° (Connect a dwell meter to the orange wire in the blue bulkhead connector (or pigtail on firewall) and ground. Set meter to 4 cylinder [yes four cylinder, if no 4cyl use 8cyl and double reading.] Aim for 40° with it swinging back and forth. )
The Idle Speed Motor will take over from there.

Details and other checks you may want to perform are listed in the Workshop Manua (http://dmctalk.org/showthread.php?2866-Searchable-Workshop-Technical-Bulletins-and-Volvo-Engine-Manuals)l D:04:15

If you don't have a dwell meter, get a loaner from AutoZone, or, or just buy the cheapest one you can find...

[Bitsyncmaster]

Usually the idle problems are idle to high. The reason I don't think your system is working is because the idle is to low when cold. Even if your "idle set screw" was backed all the way out the idle system has plenty of movement to hold 775 RPM. The idle motor normally runs a little less than 1/2 way open when the engine is cold and is almost closed when the engine is hot.

If your mixture is way rich it could also up your idle speed past the range of the idle system. But your car has the slow idle problem.

Does your idle motor make a buzzing noise? You can also feel it "buzzing" by holding your hand on it when the engine is running.

[Ron]

+1
Check the ISM for the buzz!

...I'm guessing the CO is too lean.

[Rich]

Hi all

So i can finally move on to fixing the rest of my idle issues. I just replaced my WUR and i am close to getting this idle right.

When the car is hot and running the idle is set and works fine at 750 rpms. But on cold starts it hovers around 500 rpms and is close to stalling. I think i am just not setting the idle correctly to allow the idle cpu/circuit to take over.

Dose any one know the right way to set idle? or is there something i am missing? it only takes the slightest pressure on the plate to make idle correct during warm-up.


Look in the 5th column over from the left in this page from the factory manual. Be sure to click on the image after you open it so it enlarges and you can read it clearly.

18529

Don't go fooling with the idle speed directly. The idle during warm-up is not controlled the way you think it is. The idle CO adjustment idea might work, but the chart shows 11 other possible causes of Poor Idling in Warmup Phase including such things as....wait for it....."sensor plate or control piston binding". Which seems to relate to your note about just a nudge on the sensor plate to make the cold idle behave?

[Ron]

Hmmm...I took putting the "slightest pressure on the plate" to mean it was being held there??

I worked on one where the roller the plunger rides on was froze so long that it had a flat spot on it...

[Some guy]

So i looked at it last night and i tried to adjust the CO screw, because that was the quickest way to test it. once i bring the idle back down and let it cool down. It still had the low idle at start. So i put it back to it previous location.

I think it is my ISM. It was not buzzing. it was just vibrating with the motor. I cleaned and tested it. It was moving freely and there was voltage getting to it. But i dont know where to go from here.

Where is the input to the idle control circuit? I am going to have to review the wiring harness.

I feel like i am close.

[Some guy]

I am looking over the schematic and i am seeing "IDLESPEED REGULATOR SWTICH 152" I can't find the switch to test this. could i jumper it to test if it is bad?

[Bitsyncmaster]

The ISM gets 12 volt to the center pin and the ECU will switch the outer two pins to ground at 100 Hz rate.

[DMCMW Dave]

I am looking over the schematic and i am seeing "IDLESPEED REGULATOR SWTICH 152" I can't find the switch to test this. could i jumper it to test if it is bad?

It's not really a switch. It's a thermistor and is in the y-pipe under the intake manifold.

[DeLorean03]

I am looking over the schematic and i am seeing "IDLESPEED REGULATOR SWTICH 152" I can't find the switch to test this. could i jumper it to test if it is bad?

Yes.

Follow this link. It should take you to post #2207 where I gave a brief explanation on how to do just this.

http://dmctalk.org/showthread.php?241-What-have-you-done-to-your-DeLorean-today&p=100638&viewfull=1#post100638

[Some guy]

I see, so since it is connected to the thermister, it should not have much of an effect on the idle. Open = cold and closed = hot

I think the idle speed ECU is bad. I tested the idle speed switch and that was ok. I tested the RPM signal, (The tak works and the needle moves when i connect a VOM to that terminal)

I tested the motor by quickly shorting the terminals to ground and making them move.

Then i tested DC voltage at the idle speed motor. pink wire was 12 volts. green was 5V steady and the red was 4V steady. This is leading me to believe the power transistors for switching at 100HZ are bad.

I dont have an Oscope to be 100% certain that a switching signal is making it to the transistors.

The other thing that is making me think it is bad, is the the person who had the car before me destroyed the plug on top of the idle speed motor. The wires were connected individually to each pin. Also the wrong pins.

[Bitsyncmaster]

Check those 4 and 5 volt reading with your meter set to AC volts. If they are switching, you would read a DC voltage of about those readings (DC volts does an average of AC on most meters). But the real test is to feel or hear if the ISM is buzzing. I'm pretty sure just turning the key to on (engine not running) should make the ISM buzz.

[Some guy]

I cant seem to make it buzz. I was trying last night. I know that 12v with enough current is going through the pink wire.

What i was going to try to do is short the IDLESPEED REGULATOR SWTICH 152. get that out of the way.

Then test the voltage. (AC this time)

If it is present, i am going to open the board and see if the transistors are getting hot.

I am also going to check the wire from the coil again.

[Elvis]

Hey nameless guy,

if you use "SEARCH" you will find a lot of information about that switch,
especially what it does, because there is always a misunderstanding about it.

Also how to test the ISM motor and so on. I wrote it at least 5 times and others
might habe repeated it also many times.


Why does everyone need his one idle thread ? one per week ?

Elvis & 6548 (idle motor was freezed back then, too)

[Some guy]

so i tried a new ISM and it didnt work. it is crazy. i am getting 100 hz and 2 volts ac on the red and 4v ac green leads. the pink is 12 volts. i am going to get 2 npn transistors and replace them in the circuit board. there is just nothing else that i can think of.

the new motor didn't work. it just seams like not enough energy can pass through the transistors.

[Bitsyncmaster]

so i tried a new ISM and it didnt work. it is crazy. i am getting 100 hz and 2 volts ac on the red and 4v ac green leads. the pink is 12 volts. i am going to get 2 npn transistors and replace them in the circuit board. there is just nothing else that i can think of.

the new motor didn't work. it just seams like not enough energy can pass through the transistors.

That sounds like a good plan. I would think a meter reading should show both voltages to be around 12 volts AC since each is switching from 12 volts to ground. They most likely have different duty cycles but that should not affect the voltage reading.

[Ron]

flux3d,

I moved your posts HERE (http://dmctalk.org/showthread.php?6968-Setting-Idle-(-2)-Split-from***-Setting-Idle***) to avoid confusion...

[Some guy]

Hey so i think i am on the right track, i replaced the 2 transistors with 2 NPN 4 amp transistors. As soon as i tested the circuit, i smoked the transistors. I took this as a good sign. It means there was not enough current flow before. I am replacing them with 2 that can handle 15 amps. I still have the new ISM, so i will test with that one first to be sure it is not my old motor.

[Elvis]

great step.

But why would a 4 Amp transistor blow ?
The original BD435 isn't much better and survived it 30 years :-)

(I replace them with: MJE15030G, just watch the collectors!!!!)


How are you measuring it ? with an oscilloscope or with a multimeter ?

Multimeter is not really useful here.

[Bitsyncmaster]

Make sure you get the E B C placed into the correct holes. The stock ISM draws about 800 ma.

[Some guy]

i am measuring with a digital multi meter. The transistors i picked up are similar to the one you listed.

When i come paired the 4 amp transistors to the originals, they looked the same. I agree that they should have lasted longer. I am going to test the new transistors with the new ISM.

[Bitsyncmaster]

i am measuring with a digital multi meter. The transistors i picked up are similar to the one you listed.

When i come paired the 4 amp transistors to the originals, they looked the same. I agree that they should have lasted longer. I am going to test the new transistors with the new ISM.

Do you have a data sheet or part number of the transistors you are using?

[Some guy]

I got them at Fry's "NTE electronics Inc"

NTE 331 T-NPN Si_AF PO, REG, SW

Vcbo -100V
Vceo- 100V
ic- 15A

Pd 90W
hfe- 40 min
ft -3MHZ

I dont have the spec on the 4 amp transistors. I tossed them after they burnt up, but i am going to go dumpster diving for them later.

Is it possible that a bad ISM burnt out my transistors?

[Elvis]

Everything is possible but I never heard that before.


With a multimeter this is only guessing, for this job an oszilloscope is needed.

Pictures of your new power stage would be helpful, too.

[Bitsyncmaster]

There are some diodes on the board that really help the driver design provided they are good. A bad diode will make the driver transistor get very hot. Those diodes feed the inductive spikes back into the ISM motor (load).

[Some guy]

Just to give an update

It worked, i have an idling Delorean!!!! Once i replaced the 2 transistors, the car started and went to 2000 rpms. Then i went and switched the red and green leads and BAM. The car went to about 700rpms. It was amazing!!!

It felt like the day i first started the car.

I think the transistors burnt up because they grounded out on the bad wiring job of the previous owner. (that being the biggest problem with the car)

Thank you all for the help!!! I could not have made this car work with out your help!!!

[Ron]

krs09,

I moved your posts and discussion moved HERE (http://dmctalk.org/showthread.php?7053-Idle-ECU-***SPLIT-from-setting-idle***) to avoid confusion.

[krs09]

FYI, It's not really an "idle screw" but an "idle stop screw", it's preset and should not be tampered with. (It is only for the throttle plates...holds them barely open.)

Adjust CO = Adjust mixture screw. (Always the last thing you do to the engine.)
Warm the engine fully.
Set timing: 13° ± 2° at 775 RPM.
Set CO: 35°-45° (Connect a dwell meter to the orange wire in the blue bulkhead connector (or pigtail on firewall) and ground. Set meter to 4 cylinder [yes four cylinder, if no 4cyl use 8cyl and double reading.] Aim for 40° with it swinging back and forth. )
The Idle Speed Motor will take over from there.

Details and other checks you may want to perform are listed in the Workshop Manua (http://dmctalk.org/showthread.php?2866-Searchable-Workshop-Technical-Bulletins-and-Volvo-Engine-Manuals)l D:04:15

If you don't have a dwell meter, get a loaner from AutoZone, or, or just buy the cheapest one you can find...

Im getting ready to attempt to do this again tomorrow so.. Just to be totally clear .. I fire the engine and get it warm (cooling fans kick on then off) connect my dwell meter as stated above, loosen the mixture screw and begin to make adjustments until reading is in desired area then tighten screw and disconnect dwell meter and the car should take it from there and memorize the setting? Sounds stupid I know but need to be sure. Thanks

[Ron]

Sounds like you are talking about one of the screws on the throttle lever.

The CO (or "idle mixture") screw is down in an access hole right in front of the fuel distributor (If the hole is still factory plugged, there are several threads explaining how to remove it.) You don't loosen it, you just turn it with a 3 mm allen wrench. (Make sure you remove the wrench and plug the hole while taking the reading...)

20489

[krs09]

Sounds like you are talking about one of the screws on the throttle lever.

The CO (or "idle mixture") screw is down in an access hole right in front of the fuel distributor (If the hole is still factory plugged, there are several threads explaining how to remove it.) You don't loosen it, you just turn it with a 3 mm allen wrench. (Make sure you remove the wrench and plug the hole while taking the reading...)

20489

Well the PO did a number with this car so I have a screw (small machine screw) in where the Idle mixture screw should be and it was covered with RTV when I found it. So Im not too sure how to do it now. I thought if I just unscrew it a little and adjust it that way and tighten it down when im in the "good zone".. What should I do if the PO drilled a hole (I guess) where the Idle mixture plug used to be?? Thanks Ron.

[Ron]

There is already a hole there from the factory. They install a tamper resistant plug. If the CO must be reset, most people discard the factory plug and use one of these (http://store.delorean.com/p-6399-plug-removeable.aspx). He just used a machine screw. Remove it and the screw you want is down in the hole a inch or so. Turn the screw a little at a time until you see the dwell meter swinging back and forth between 35° & 45°. Then remove the allen wrench and plug the hole with your finger to double check the reading. (Re-plug the hole since it is a vacuum leak.)

[krs09]

There is already a hole there from the factory. They install a tamper resistant plug. If the CO must be reset, most people discard the factory plug and use one of these (http://store.delorean.com/p-6399-plug-removeable.aspx). He just used a machine screw. Remove it and the screw you want is down in the hole a inch or so. Turn the screw a little at a time until you see the dwell meter swinging back and forth between 35° & 45°. Then remove the allen wrench and plug the hole with your finger to double check the reading. (Re-plug the hole since it is a vacuum leak.)

Ron ... That is the answer Ive been waiting for!!:nana1: Now all the other stuff makes sense.. I never knew there was a allen adjustment in that hole. Thank you so much. I hooked up the dwell meter and can bearly get it to move from the 5degree mark but the car idled properly for the first time since putting the engine back together (it would surge like crazy) and really got rid of the raw gas smell ive had after it idled for a while. Im going to double check in the beginning of the week. I did manage to get the dwell to swing from 20d mark to the 30d mark but it ran like shit. Wonder what that's all about .. Maybe I should check to timing again? Thanks again so much.:notworthy:

[Ron]

Yes, check the timing...the dwell should always be the last adjustment, with the engine warmed up. Use four (4) cylinder setting!

[David T]

Yes, check the timing...the dwell should always be the last adjustment, with the engine warmed up. Use four (4) cylinder setting!

If the motor was running way too rich you may have contaminated the O2 sensor and now it will be difficult to read and adjust the duty cycle. You may have to replace the O2 sensor. One trick you can use before you replace it. Remove it and heat it up with a propane torch to burn off as much of the contamination as you can. It won't make it work like new but it can make it serviceable. As Ron says, you replace everything and do every other adjustment first before attempting to set the mixture. While you are checking base timing make sure the mechanical and vacuum advance is also working.
David Teitelbaum