Setting Idle (#2) Split from***Setting Idle***

[flux3d]

I'm having the same problem with the car idling when cold. I find that I have to just keep my foot on the gas in order to raise the idle, or it hunts between 500 and 1000, getting ever more erratic in its swing until it falls below 500 and stalls. After a couple of minutes with me putting my foot gently on the gas it settles and idles fine.

I've check the idle motor, and that hums as soon as the ignition is turned to the second position. Vac lines seem ok, although I admit not knowing how to check them for a leak does make me wonder if this is where the problem might be.

Any ideas?

[flux3d]

Here is a video of my similar problem. I was going to start another thread, but it might be similar to the OP's problem.


http://www.youtube.com/watch?v=jsSivyedZAk&feature=youtu.be

[flux3d]

and the second video, this time looking at the engine.


http://www.youtube.com/watch?v=BkJ76zuehq4&feature=youtu.be

[Ron]

Have you performed the checks in the other thread?

[Elvis]

Hey I think this is great to post videos about the problems
instead of (sometimes) wrong descriptions.

But as Ron already said - did you check the standard stuff so far ?

We really have at least one idle problem per week. Did you read some
of them ?


BTW - nice clean engine, did you work recently on it ?
And the buzzing is NOT the idle motor, because that does not shut off
when the engine stalls.

[flux3d]

I read about every post on here daily, much to the chagrin of my partner who thinks I'm obsessed with the car! So far the previous poster on the original thread was the closest its come to describing my problem. From looking on here and other forums I've narrowed it down to a list of possibles:

1: Could be a vacuum leak somewhere. I've done a visual inspection, but nothing seemed to stand out. Does anyone have a way of testing for leaks? I had heard that putting a bit of water on a suspected area could work?

2: The WUR/CPR could have a blocked filter or be faulty. This would cause increased pressure during the warm-up period, and therefore cause the engine to run leaner and stall.

3: A problem with the fuel pressure generally. The pump seems good, but I do have the usual warm start issue associated with a bad fuel accumulator. Can this same fault effect cold starting? I wouldn't have thought so.

4: A faulty idle speed motor. However, as per the previous post this hums away fine as far as I can tell. Maybe I also need to check the voltage on it, but to be honest I'm not too sure how to do this.

Any other ideas?

Mark

[Ron]

Vacuum can be checked with water outside (watching and listening to it) or by blowing smoke into the engine (watching for it to escape). For the rest, check the timing, pressures, and CO, in that order and the problem should raise its ugly head... If not we can help you find it.

[Elvis]

ISM is OK otherwise it wouldn't be hunting.
BTW - How to test the motor has been explained many times, but that ain't your problem.



One of the first things I'd check is the mixture adjusting screw - is the plug in there ?

Or are there other vacuum leaks ? (Spray test done ? )

Your engine looks so clean - did you work on it lately and when did that problem start ?

I'm with you. I'd expect it's something mixture related.

[Ron]

I'm with you. I'd expect it's something mixture related.I have to admit I would probably nudge the CO clockwise...But, I'm not sure he (you) has the tools to get it back to where it was if that don't help (it is all but impossible to move it back w/o a meter...)-- Don't want to complicate the problem(s) by adding another one. Systematic testing pays off in the long run :dunno:

[flux3d]

I think the engine looks cleaner in the video than it really is. I'd given it a wipe over with de-greaser just before doing the video as the car was going out for a show. Its had the same cold start problem Since I got her in December last year, so its nothing new.

As for the mixture screw, I think this is as it was when new, untouched. Do i need to drill it out or something to access the screw?

[Ron]

As for the mixture screw, I think this is as it was when new, untouched. Do i need to drill it
out or something to access the screw?
Some people drill them partially through, run a tap in it, and pull it out with a small bolt...

Is your CO/Dwell off???

[Elvis]

hm, you think but you don't know it ?

do you know where to find it ?

[flux3d]

I pulled both of the fuel lines off the CPR unit yesterday to have a look at the larger, intake side has the biggest block of copper/brass gunk blocking it, just like this you can see in this image:

18847

This is NOT my CPR, but the blockage looks just like it. My question is how do I take it apart to get his stuff out?

[Elvis]

Let's assume this does not belong there - where should it come from ?

[flux3d]

Well, I ended up checking the car out again on the weekend. One thing that I did find is that the three large brass mixture screws had been backed out quite a way, which would probably constitute a vacuum leak. Plus the vac line between the idle speed motor and the cold start valve was a bit loose, so a jubilee clip helped sort that.

I also removed the mixture adjustment screw cap and adjusted it. I unplugged the O2 sensor, got her up to temp and then adjusted it anti-clockwise until it stalled, and then back round clockwise until it again stalled. Marked both points and set it at the half way point.

This seems to have helped, although bad weather has stopped me really checking out what effect the changes have had. One thing that I'm concerned about is the ISM. When I turn the ignition to position two it hums, but soon quits doing that. Taking it off the vac pipes and looking down to where the valve is I can't see this valve moving at all. It seems to do nothing?

http://www.flux3d.co.uk/VIN10719/ISM_1.JPG

Can it be cleaned and restored, or is it a new one? They look expensive, especially on Delorean.eu. Martin here in the UK has a replacement at £159, which seems more reasonable, but a fix would be better.

[Ron]

You should set your CO with a dwell meter. It's simple to do if you can borrow a meter.

[flux3d]

I do have one I can borrow, so how do you set it Ron? I can do it over the weekend and make sure its correct.

What about the ISM? Any ideas?

[dmc6960]

Technically those brass screws are never a vacuum leak unless their o-rings are shot. They bypass already metered air through the throttle body. IF, and I emphasis the IF, everything else is working as it should those screws can actually help the stock idle system. But first you really should make sure there are no real vacuum leaks, and stock idle system is working as it should, and you have the CO properly set.

About your idle motor, use a plastic or wooden stik to try and turn the motor fully opened. The reattach, turn on ignition and watch what happens. It will probably close about half way, then should open up as the computer sees and RPM underspeed.

[Roman Legion]

So how do you adjust the idle on the car? Does it work anything like my motorcycle (I twist the little thing at the bottom of my carb to lower/ raise it). If you keep the accelerator pushed in a bit at 1-3k RPM, could you just warm the engine up as I do with my bike (Which I have a choke for, but warms the engine up from a cold start)? I'm a newb to this stuff, but I'm learning more and more everyday, so please bear with me here.

[Ron]

You don't really, it is automatic. Lots of threads on it here. Search (https://www.google.com/search?hl=en&as_q=set+idle&as_epq=&as_oq=&as_eq=&as_nlo=&as_nhi=&lr=&cr=&as_qdr=all&as_sitesearch=dmctalk.org&as_occt=any&safe=images&tbs=&as_filetype=&as_rights=) and you will find.
Check this one out. (http://dmctalk.org/showthread.php?5064-Adjusting-Idle-Speed&p=71917&viewfull=1#post71917)

[David T]

You cannot set the mixture that way. There are plenty of posts on how to set it initially to get the motor to run and then how to set it using a dwell meter. If it was still sealed you probably should have left it alone (it is a VERY sensitive adjustment). I have yet to see anyone "fix" a car by "screwing" around with that adjustment. There is something wrong and you cannot get the car to run better by messing with that screw. The three brass screws should be turned clockwise till they seat lightly (don't overtighten them or they will break).One thing you can count on is each week there will be a post on mixture, idle, hot restart, and in the summer on the A/C. These topics just keep reoccurring. It would be nice if we had a fault tree we cold just send them to. Everyone thinks they are the first to have these problems.
David Teitelbaum

[krs09]

You can try to clean it. I had a similar issue where the valve seemed to stick and didnt have enough power to move from open to closed. I took it out and sprayed a little intake cleaner and lube in the valve reached in with a flat head screw driver (carefully) and moved it closed and repeated, gave it a little shake and I could hear it moving just by lightly shaking it (was solid before). When I installed it and turned the key to power I ran to watch it move with the hose (that connects to the CSV) removed and watched it do a full cycle from open to close, it never did that before. It really seemd to help my idle issue.

[flux3d]

Well, finally managed to get round to looking at the engine again yesterday. This is what I found.

I dismantled the ISM again to check it all over. I'd sprayed in loads of release fluid last time I had it off, and to my joy this time the valve swung back and forth with ease. Sure enough when I connected to the electrical plug and turned the ignition to position two the valve swung quickly round to the closed position and held there. Seems to be working at least. Not tried the resistance or 12V test Admin, I didn't have time, but this seems right, yeh?

Checked all the vac pipes as per the diagram (none on my engine cover so ordered one from Ed over at delorean.eu). All seem good.

Then tried the mixture out again, but this time with the dwell meter connected. First with the O2 sensor disconnected and the engine warmed up. With this set-up the dwell read around the 40 mark, and with the full throttle switch engaged about 51. Adjustment of the mixture did nothing to alter this reading. Then I connected the O2 sensor again and started her up. The dwell reading was very low, bottoming out the needle at 30 or below! Obviously it was very far off. At first I thought I must have a faulty meter (it is quite a few years old), but turning the mixture screw anti-clockwise I managed to get the reading to finally swing between 45 and 55. It does jump up a fair bit when the fans kick in, but I imagine this is what meant to happen.

Anyway, done another video to show the results.

Taking the car out for a quick trip it seemed quite a bit better.


http://www.youtube.com/watch?v=1fr0z1NqHX8&feature=youtu.be

[Ron]

Can't tell for sure in the vid, but are you plugging the hole for the allen wrench when you take a reading? You should (vacuum leak).

[jawn101]

It does jump up a fair bit when the fans kick in, but I imagine this is what meant to happen.

I'm not so sure on that - I don't think the fans figure into the circuit at all. You may be seeing the effect of bad grounds/voltage drop impacting your reading when the fans come on, but I don't think the mixture or duty cycle is (rather, shouldn't be) changing because of the fans.

[Ron]

I guess it is the load from the alternator and the ISM compensating...

[flux3d]

Yes Ron, that was what in was thinking, the alternator load would probably cause the jump from the ISM. At least it indicates it's working well.

People have said it sounds like the valve clearance needs work.

Yeah the hole is plugged with the Allen key and tape during the adjustment.