NB Idle valve issue - PWM valve running DIYPNP MS2

wydra · Postby **wydra** » Fri Aug 23, 2013 1:21 am

Hey guys,

So I have been running the DIYPNP MS2 on my '00 NB for a while now and things are running well.
I have also got the turbo conversion all finished and a reasonable tune in place (running low boost 9/10 psi).

I thought it was time to finish off all the small stuff and get the car a little more refined but now have run into an issue with the IAC PWM valve. I see a lot of people have trouble tuning closed loop PWM but I am having a problem before even getting this far, its like my valve isn't responding to the ECU.

So I set the ECU to PWM warmup only as some have suggested, but the valve doesn't seem to be doing anything.
I thought the valve might be dead so with the engine running I disconnected the wire to the valve and put 12V across it, you could hear a click as the valve opened and the revs shoot upto 4-5000rpm.
Put a multimeter across one of the pins that usually go into the valve and there is a constant 12V as you would expect.
Put the multimeter across the two pins and get 7.5/8.5V, about what I would expect to see with PWM (unfortunately I don't have a spectrometer to check this 100%).

I found there is a Idle Valve Test so ran this but no changes I make in this do anything at all.

As a test I enabled the FIDLE in the output settings and the ECU throws out 12V to the valve and revs jump up to 4-5000rpm.

So now I am a bit confused.
I know the ECU is actually connected to the valve but I cant control it correctly. Has anyone come across something like this?
I'm pretty sure the valve was working fine on the original ECU about 6 months ago.

Is there anyone out there that might be able to shed some light on this?
Ideas?

Cheers,
Dale

Postby **NitroDann** » Fri Aug 23, 2013 1:37 am

This is a very well worded question and would be answered immediately by experienced users at MTnet, if you dont have luck here.

Ive not a lot of experience fine tuning Nb with that specific version so Im sorry I cannot be of assistance.

Dann

geofiz · Postby **geofiz** » Fri Aug 23, 2013 2:31 am

Try posting it on the megasquirt forum.

wydra · Postby **wydra** » Fri Aug 23, 2013 12:54 pm

Thanks guys, I will throw the question over to those forums today.

If anyone else has some insight as to what might be going on, please feel free to chime in

wydra · Postby **wydra** » Wed Aug 28, 2013 11:41 pm

I have removed the ECU from the car and put the original ECU back in to test the valve, it appears to be working fine.

Now I am connected to the DIYPNP MS2 via RS232 and have it on a 12V power supply.

When I measure a 12V source on the board it is reading 12.01V on the DMM. When I measure between the IAC output and 12V I get a reading of 10.61V regardless what I set the frequency and PWM % too in TunerStudio. This is also true for when I try and use the Idle Output Test with any settings.

The only way I have been able to get the IAC voltage to change is if I enable the FIDLE output as shown in this screenshot. Something that I think is strange is when you disable the FIDLE output it stays at 12V until you reset the ECU (the same as what it was doing on the car).

Idle5.jpg

Now the ECU is off the car and I am bench testing is there anyway I can test the IAC operation?
Does anyone know what the IAC point on the sequential injector board is for? (I have not connected anything to it)
Is there something stupid I might have done that I can check for?

wydra · Postby **wydra** » Mon Sep 02, 2013 1:05 am

So I have been told the hardware is doing what it should be doing and this is probably Software related.
Great, software should be easier to fix fight?
Can anyway shed any light on what might be going on?

I have upgraded firmware to 3.2.5 with the same results.
Not really sure where to go from here.

wydra · Postby **wydra** » Thu Sep 05, 2013 9:13 pm

I plugged the ECU back into the car to get a log of it trying to control the valve.
I started up the engine and started to log. The valve remained shut and I needed to add accelerator to keep the revs up just as it did before so I stopped the log.
I then turned FIDLE output to 'ON' and the revs shot straight up to 5-6k rpm just as it did before so I switched the engine off.
Then I powered up the ECU again to turn off the FIDLE off and TunerStudio said there was a config error (obviously for having the FIDLE enabled and Idle control on).
I turned FIDLE off and just left PWM Warmup on.

THEN....

When I restarted the engine, the valve is working!
Went into valve test and the valve is following what percentage I set it to with revs increasing and decreasing as I change the figures.

I'm not really sure what is different to before as I have tried this exact procedure with the older 3.2.1 firmware so maybe it is something to do with the new firmware?

Thanks to everyone that tried to help, all is now well

wydra · Postby **wydra** » Mon Feb 03, 2014 3:03 pm

Just for some closure on this topic.
I spent a lot of time getting my PID settings tuned and managed to get the idle 90% there. It would never stall while driving and was quick enough to catch the A/C BUT it would oscillate. At the start the oscillations where quite bad but with some tuning of spark and fuel (had to run it reasonably rich) I got it where it would only oscillate a hundred rpm or so.
The only thing that reduced the oscillation was reducing the frequency multiplier. The suggested is 16x and anything under 13x the valve sounded like a plane propeller so I settled with 13x and dealt with the oscillations for a while.
I then bought a JBPerf PWM converter Board,
http://www.jbperf.com/pwm_converter/index.html
set it to 16x and 1x on the MS (and inverted the signal) and now my idle is 100%.

Awesome! I Can’t recommend this enough for anyone having issues getting their idle dialled in.
I was even able to lean out the idle A/F to what it should be and it is still rock solid.