1999 DIYPNP idle valve issue (now with MSQ)
 

I am having a hard time getting the idle valve to function. I have gone through all the Mega Miata blog posts and the information here on this site. I was able to get the idle valve to function correctly in the previous 3 DIYPNP's that I have built, one for my racecar and two for friends, but this one has got me stumped. I will post up my msq later this afternoon, when I have access to my tuning laptop. Basically, when I have the idle valve set to 480hz, and I do the idle valve test, I am getting little to no action until I get very high in the duty cycle. From 0-40 there is no change, from 41-75 there is a 10-20rpm change and from 76-88 the rpms go up as expected, but from 88-99 there is a LARGE jump, like from 1500 to 4000rpms. Also, when I start the car, the idle valve does not run and fast idle for a brief moment like it does on all the other installs I have done. I am thinking it may be the idle valve itself as it has 190,000 miles on it, but I want to make sure it is not a simple setting I am missing. I have tried to run the idle valve inverted as well and I get similar behavior in the test mode, but the numbers are reversed in 100% gives no valve action and 0% is fully open. Also, no matter what frequency I put, the valve makes noise.

Thanks for any suggestions and I will get my MSQ posted up this afternoon.

did you install the flyback diode?<br /><br />NB valve likes to operate between ~60-90% PWM. I tend to use the 511Hz option. Sounds like yours may have an issue...

Diode is installed and I do not have any higher frequency to chose from other than 480hz. Is there another firmware that can get me there or is there a script change needed via the notepad edit of the MSQ file?

Here is my most recent MSQ file. I did some playing this afternoon with voltage compensation idle values and did not get much results. Please take a look and tell me what little setting I am missing!

Thanks for your help.

Attachment 178655
Attachment 178656

Can you also post a data log of what's going on?

I am getting little to no action of the idle valve. I have to hold the revs up first thing in the morning until a little warm and then it will maintain its own idle. What spefically would you like to see in the log? Cold or hot, a rev and return to idle a few times?

Thanks for the help.

I'd recommend trying to move the IAC valve with idle test mode and logging how much the actual RPM changes.

Will do. Do you have a preference from 100 down or ~35 up?

Here is a log of an idle valve test from 100 to 0, please see attached.

Attachment 178662

Yeah, it's being pretty touchy. How exactly is the flyback diode installed in the DIYPNP? And what happens if you try a lower frequency?

A lower frequency will cause the valve to make more noise, but lowers the range at which the valve responds within test mode, but I still get no idle increase even with the new values from the test mode entered.
When I get home this evening, I will remove the DIYPNP and open up the case and report back with the findings.

My minimum valve duty is set to 25% and maximum to 85%

When i installed my skunk2 tb i hooked the IAC up and fired up idle valve test mode and checked within what range it moved and this is wat i came up with. Im using the 511hz freq

I forgot my Daughter had a school event yesterday evening and I did not have time to yank the DIYPNP and crack it open.

Just to update the post. I have not been able to get the ECU out of the car and open it up. I hope to be able to that this evening. Lots of family stuff going on.

Ok, update time! Lesson for the day... When you guy second hand devices do NOT assume the previous owner assembled the device correctly. I opened up the unit and there is no diode. In its place there is a resistor to 5v. I de-soldered the resistor and soldered in a diode I had from other Megasquirt builds. Put the unit back in the car and I now have a normally functioning idle valve! Thanks for all who helped.

You sir, earned another cat! Support like yours is why I buy from DIY Autotune.

I said it in post #2...

You get a cat too. Thanks for them help. Sorry I missed it the first time.