Idle seems to be in reverse!!
 

Hi Guys, I wonder if someone could help me please. I built and fitted my MS1 over a year ago, it is all running fine apart from the Idle which seems to work in reverse, when I start from cold the revs are low (850-900rpm) and when the engine gets to normal operating temperature the idle sits at 1200-1250rpm).

The car is a 1993 1.6 with FM hardware and an FMIC. This is what I have tried so far to try to cure the problem:

1. Checked the MS build and it seems fine.

2. Changed the polarity of the Diode on the 2 wires on the Idle valve to see if I had fitted it wrong.

3. Applied voltage to the idle valve and I can hear the solenoid working (I also changed the idle valve).

All of the above made no difference. I have asked a few MS Guru's here in the UK and we still cant seem to find the problem. I am about to order the MS2 daughter board so I can use the EBC but I would really love to get rid of this final problem before I do that, very grateful for any help.
Cheers
Barry

Please post a copy of your MSQ so we can check your idle speed settings. It's quite possible to tell the idle solenoid to operate in reverse (or not operate at all).

When my idle control is turned off it will idle a few 100 rpms lower when cold.

Here you go Matt:

Attachment 19658

Nothing blatantly wrong with the settings; can you post a data log of this behavior?

Will do Matt, will a 10 min log from first cranking suffice?
Cheers
Barry

My guess is that your idle speed screw is open too far and all your idle control circuit is doing is sitting at minimum trying to fruitlessly bring the idle speed down. Try this:

1. Set "When to use PWM idle" to "Warmup Only."
2. Your "Idle duty at lower temp (dc)" and "Idle duty at upper temp (dc)" will now be un-grayed. Leave your existing setting for lower temp but change your setting for upper temp to 19 (to match your "Minimum (dc)").
3. Change your "*Fast Idle (lower) Temp (F)" from 54 to 130. Remember, it's °F, not °C.
4. Change your "*Slow Idle (upper) Temp (F)" from 71 to 160. Same comment about units.
5. What the squirt will now do is slowly change the idle control valve duty cycle from 27 when at or below 130°F coolant temperature to 19 when at or above 160°F coolant temperature. The dc change will be slow and steady without oscillations (you are now running open loop). Setup your gauges so you can monitor coolant temperature and dc to confirm proper operation. If everything is correct, the higher dc will give more RPM.
6. Once you're stabilized and warmed-up, with all accessories, lights and fans off (minimum alternator load), you can turn the idle screw in to achieve the desired idle RPM.
7. Now you can return to "Closed loop only" and start fiddling with those adjustments. However, if you're not running AC, you might consider just staying in "Warmup only." Many users find this mode to be perfectly satisfactory.

Hornetball, thanks for that, my idle screw is almost fully screwed in but I will try what you suggest. I have just tried to upload a 10 min datalog to show this happening but the upload keeps failing, I dont know why!!
Barry

BTW, when operating in "Warmup only" mode, you can manually control the signal to your idle control valve (once you're warmed up) by changing the "Idle duty at upper temp (dc)" value. This will let you troubleshoot if needed.

Hornetball, thanks. When you say:

3. Change your "*Fast Idle (lower) Temp (F)" from 54 to 130. Remember, it's °F, not °C.
4. Change your "*Slow Idle (upper) Temp (F)" from 71 to 160. Same comment about units.

How do I change it from C to F?, the settings are in C, do I just change the54 to 130 and the 71 to 160?

Sorry for the bone questions!!
Barry

Oh. Well, you're software must be different then. When I opened your *.msq in Megatune 2.25, those values were shown in F. I doubt that the squirt reads the *.msq differently, so I wonder if there is a bug in your tuning software so that when you think you're setting up in C, you're actually burning values in F?

Anyway, it's easy enough to test. Just do a warmup cycle in "Warmup only" mode and observe/chart the dc behavior. That will tell you what it is really doing.

What you're really trying to achieve here is a way to steady state the Idle dc under your control so you can troubleshoot what's going on and get your idle speed screw set. From that standpoint, fine tuning the Fast Idle and Slow Idle coolant temperatures can be done later.

C and F are local settings.

And to keep going . . . .

It's not good that your idle speed screw is almost completely in. That makes it succeptible to changing the size of the orifice as the respective needle and seat temperatures change. Make sure your idle spark advance is set so that the idle speed screw is at least one turn open to get a decent, unloaded idle speed at 19dc. You'll probably have to retard a bit.

I've seen Brain post before that he runs in "Warmup only" mode with an idle spark advance around 12°BTDC. He also likes to keep all the advance bins in the idle area the same to minimize variability. Brain is someone we should listen to.

I acutally use table-switching on my spark table. I keep all idle cells at 12° (use no spark advance anymore). The less the timing fluctuates, the more stable the idle is. Then I trigger table-switching when the A/C is activated and then hold 18°. My idle is as smooth as Hustler's mouth. But I use PID closed loop idle.

So just leave the fast and slow idle as they are and just change to warm up only?

Brain - I have removed my A/C so that is not an issue.....

Barry

Yes, I would just leave as is and then data log idle dc vs. coolant temperature so you know what you have.

Bottom line, "Warmup only" gives you control of dc. You can raise and lower it at will. This will let you troubleshoot what's happening. If you are getting the expected response (i.e., increase in dc = increase in RPM), then you can move on to setting the idle screw and fine tuning the other idle settings. If you do not get the expected response, then there is something else wrong that is reversing the response of the idle air control valve to the squirt commands.

Let us know!

Cheers Bud, appreciate the advice and I will try what you have suggested. I have a datalog of this happening but I cant seem to upload it (keeps failing?) if you are interested I can email it to you or matt if you pm me your email addresses. Thanks for your time....
Barry

OK, just tried it on warm up only and messed with the dc and it dident change anything, I brought up a idle dc gauge and I can see the needle (%) moving down as the temp increases but it dident seem to change the rpm. I have emailed my datalog to Matt so hopefully he will be able to spot something. This is driving me nuts!!
Barry

Sounds like the idle air control valve is completely unresponsive to the squirt. If you unplug the idle air control valve, does it change anything?

No, I have just tried that and there is no change in RPM at all?

Well, you've found your problem then. This jives with you symtoms. With the idle air control valve out of action, you're idling on a fixed orifice. In this case, your idle speed will be lower at cold temperatures and higher when you're warmed up.

Next steps:
1. Monitor pins at idle air control valve for signal. You'll probably need a scope for this.
2. If signal present and correct, then swap idle air contol valve.
3. If signal not present, see if signal present at squirt pins.
4. If signal present at squirt pins, troubleshoot wiring.
5. If signal not present at squirt pins, time to dig into squirt.

If I had to guess, given that this is a newly built MS where this function has never worked, I'd say the problem is internal to the MS. Hopefully, you have the tools for this or a EE friend that can help. But at least you've solved the main part of the mystery and you are no longer changing MS parameters and scratching your head.

I just reread your original post, and it seems you've already confirmed a good idle air control valve.

When you did the following:

"2. Changed the polarity of the Diode on the 2 wires on the Idle valve to see if I had fitted it wrong."

you could easily have damaged something. If this diode goes across the solenoid wires, then it is there to allow high voltages that result from the breakdown of the magnetic field in the solenoid winding to dissipate (think ignition coil -- all coils, such as those in the solenoid of the idle air control valve, produce these voltages). By reversing or removing the diode, you forced that voltage to dissipate through the electronics of the MS.

Thanks for the replies bud, I have the iac diode between the 2 wires at the iac connector, I think we are thinking the same thing. would the diode have been damaged or something more serious in the MS?
Barry

It would be something more serious. The usual failure mode for a diode is open -- so it shouldn't knock your iac valve out of action even if it is blown. Easy to tell with a multimeter.

However, you mentioned having the symptoms even before you touched the diode. So, something would have been wrong prior, and is still probably wrong now. Given that your iac valve has always been non-responsive, there may not be any further damage from the diode experiment. We can hope, right?

Anyway, you've exhausted my EE knowledge. Probably time to engage some of the more knowledgeable types like Matt or Brain.

Bud, just like to say a big thank you for your time:beer: Appreciated...
Barry

I may see if I can buy the IAC component pack for the ms and renew those parts to see if that works...

Have you checked to see if the "air valve" on the manifold is operating correctly? Water going thru? gaskets ok?

I have recently change the inlet manifold and renewed all of the gaskets so it should be OK.

Uhhhhhh . . . the Air Valve that Older Guy is talking about is an active mechanical component. Simply renewing gaskets is not a guarantee that it is working. It could very well be stuck.

I recommend the following website to help you understand the idle mechanisms on your engine:

http://www.miata.net/garage/isc.html

It will help you, I promise.

Could someone have a quick look at the photos to see if any obvious idle mod issues are evident, many thanks
Barry

Is the R39 jumper in place? The wires are in the way but it almost looks like it's missing.

Hi Matt,
Following the instructions here http://www.megamanual.com/index.html

It says: Do not install Q20, do not install D8, and jumper R39 as well, I may have read that as 'do not jumper R39', I will need to whip out my MS and confirm if I have done it or not.

Could this be my problem?
Barry

You have the thing programmed for the Southern Hemisphere! Just click Northern and all will be well.

Found another image, I did jump R39....
Barry

I take it that was an 'attempt' at humour!!.......:giggle:

I have the 1N4001 diode across the 2 wires that go to the idle valve connector, is that correct?