Trouble with PWM Idle Valve with MS2Extra v2.2 PCB

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wae
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Trouble with PWM Idle Valve with MS2Extra v2.2 PCB

Post by wae »

I have MS2/Extra 3.4.2 loaded on a v2.2 PCB and I'm trying to add control of the idle valve. It is a valve from a 2005 PT Cruiser turbo-lite motor which is a 2 wire PWM valve. I purchased and installed the mod kit from DIYAutoTune to replace Q5 with the TIP120 transistor, however, on my first attempt, I failed to wire the pins properly, literally getting my wires crossed. Assuming that it wasn't working because the transistor was mi-wired, I found another TIP120 transistor and installed it properly. I went in to the idle valve testmode in TunerStudio and attempted to set the duty cycle to 30% and enable testing. Instead of getting any sort of reaction from the idle valve, I got smoke from the transistor. So I put another TIP120 in and this time tried just starting the car and it very much acts like the idle valve isn't working - I need to crack the throttle a bit to get it to start and to keep it idling. It didn't start smoking, but the transistor was getting super hot. When I hook 12V directly to the idle valve, it makes plenty of noise, so I'm assuming that means the valve is functional.

What am I doing wrong here or what should I be checking? I've attached my .MSQ in the event that I'm not configuring it properly.
Matt Cramer
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Re: Trouble with PWM Idle Valve with MS2Extra v2.2 PCB

Post by Matt Cramer »

First, try checking the output with a test light in output test mode - does switching the output on make the light come on? Does the light switch off properly when the output is switched off?
Matt Cramer -1966 Dodge Dart slant six running on MS3X
wae
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Re: Trouble with PWM Idle Valve with MS2Extra v2.2 PCB

Post by wae »

I put a test light on the output - positive to a fused 12V and the negative side to the FIDLE wire. As soon as I switched on the ignition, the light came on. Checking a second time, I got about 2.2-2.3 volts as well. When I went into the testmodes and set the duty cycle to 0%, the light went off but when I disabled testing, it came back on. The light seems to come on when I get to about 5% on the duty cycle in testing - it's dim, but it gets brighter as I increase duty cycle. The transistor also got super hot again, jut in the handful of seconds that it took me to do those tests.
Matt Cramer
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Re: Trouble with PWM Idle Valve with MS2Extra v2.2 PCB

Post by Matt Cramer »

Make sure the transistor is bolted to the case or other suitable heat sinking.
Matt Cramer -1966 Dodge Dart slant six running on MS3X
wae
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Re: Trouble with PWM Idle Valve with MS2Extra v2.2 PCB

Post by wae »

Yep, I've got it slathered in thermal grease, the mica insulator is in place (I verified no continuity between the case and the transistor), and I'm using the nylon nut and bolt to keep it in place.
slow_hemi6
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Re: Trouble with PWM Idle Valve with MS2Extra v2.2 PCB

Post by slow_hemi6 »

How many watts is the globe in your test light?
Find the Manuals up top under Quick links: Manuals. :RTFM:
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wae
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Re: Trouble with PWM Idle Valve with MS2Extra v2.2 PCB

Post by wae »

I don't really know. It's an LED that I scavenged from a computer case a while back and put a 1k resistor on.

Regardless, when I tell tunerstudio to turn it off, shouldn't the light go out and the transistor stop receiving power?
slow_hemi6
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Re: Trouble with PWM Idle Valve with MS2Extra v2.2 PCB

Post by slow_hemi6 »

If it is a LED then the current drawn will be minimal. That should not cause overheating of a TIP12x. Yes it should turn off when turned off in test mode. Where did you source your TIP120's from?
Find the Manuals up top under Quick links: Manuals. :RTFM:
Cheers Luke
wae
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Re: Trouble with PWM Idle Valve with MS2Extra v2.2 PCB

Post by wae »

I've got one that I sourced from DIYAutoTune, but that's the one I soldered in reversing the base and collector. The replacements that I've tried have been sourced from an ebay seller. The datasheet is at http://www.taydaelectronics.com/datasheets/A-916.pdf. I did doublecheck to make sure that the transistor is actually marked as a TIP120 and that nothing got switched around.
wae
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Re: Trouble with PWM Idle Valve with MS2Extra v2.2 PCB

Post by wae »

And another update... I figured I would just try to get things running without any idle control because race season is approaching quickly. I turned the idle control function off in TunerStudio and disconnected the wiring completely from the IAC - the wire that went from the IAC connector to +12V is no longer connected to anything and the FIDLE port is snipped before the IAC connector as well so there is no chance of anything backfeeding through the wire. The car started up and ran for about 30-45 seconds before I noticed copious amounts of smoke coming from that TIP120 transistor so I shut it down.

Another bit of information that may or may not be relevant: While I had the thing open, I added not just the IAC control but also tach output and knock sensor input. Tach control is a 2N2222A transistor with the emitter wired to a 10k resistor and to X14 with the other end of the 10k resistor wired to the hole to the right of X13 (which is also wired to JP1 port 6 to provide the +12V to the MS2 daughterboard). The base is wired to a 1k resistor and then to X7. The collector is wired to the bottom of D1 (D1 is not installed on the board, but appears to provide ground).

Knock input is a jumper from X13 to X6.

When the car runs, the tach in TunerStudio is rock solid but the tach in the dash is super jumpy and all over the board - if I rev to about 2k RPM, the tach jumps to 8K and hangs there for a while even after the car idles back down to 600 RPM). This resistor combination is one that pretty much every other post I've seen about driving a 1gn Neon tach uses, so I'm suspecting there is something else going on.
slow_hemi6
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Re: Trouble with PWM Idle Valve with MS2Extra v2.2 PCB

Post by slow_hemi6 »

What about the flyback diode for the tip120, is it installed the right way around? The stripe end has to be connected to 12v and non stripe end to collector.
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Cheers Luke
wae
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Re: Trouble with PWM Idle Valve with MS2Extra v2.2 PCB

Post by wae »

slow_hemi6 wrote:What about the flyback diode for the tip120, is it installed the right way around? The stripe end has to be connected to 12v and non stripe end to collector.
I did not install the diode because I read here: https://www.diyautotune.com/product/meg ... od-kit-39/ that it is not needed for a 2.2 board. I can certainly install it if that's incorrect, but even if it was there would I be smoking the transistor with nothing connected to the FIDLE pin and the FIDLE function turned off?
slow_hemi6
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Re: Trouble with PWM Idle Valve with MS2Extra v2.2 PCB

Post by slow_hemi6 »

Ah yes the V2.2 Fidle already has D9 in it's circuit. It is connected to the tip120 collector and 12V so if it was in backwards then it could be a current path. Tip can really only smoke with a current path through it.
Find the Manuals up top under Quick links: Manuals. :RTFM:
Cheers Luke
wae
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Joined: Sat Apr 30, 2016 1:50 pm

Re: Trouble with PWM Idle Valve with MS2Extra v2.2 PCB

Post by wae »

For my next trick, I removed the jumper wire that the MSII daughterboard install instructions had me place between the pin to the right of X13 and JP1-6 and I removed the TIP120. That smoothed out the tach signal a bit and the car runs, although since there's no way to manually adjust the idle, starting is a bit hard and idle is a couple hundred RPM too low. My next experiment was to re-install the TIP120 while that jumper wire was missing. This time, when I run the testmode, the test light does turn on and off. The transistor gets a little bit hot but does not smoke or catch fire, so that's an improvement! I can hear a buzzing or whine coming from the Megasquirt board when I set the testmode duty cycle and enable testing however the idle valve doesn't appear to actually do anything and makes no noises. I tried sending 12V directly to the IAC again (with Megasquirt disconnected from the IAC of course) and it does make some nice buzzing noises. I also tried reversing the +12V and the FIDLE connections at the idle valve to see if that would make a difference but still nothing. During all this activity, the test light does seem to be turning on and off at the appropriate times, so perhaps now my issue is that my PWM valve settings are incorrect? The valve is the stock valve from a 2005 PT Cruiser turbo-lite (which, in theory, should be electrically identical to the SRT-4 valve) and my settings look like this:

Image

I've found other posts indicating that setting the idle valve frequency to 250Hz is the right setting and 252Hz is the closest to that available from which to choose in the dropdown box, but other than that I'm not sure that I've got the right settings.

NINJA EDIT: Oh, and here's another weird thing: When I put the TIP120 back in to test, the tach got all jumpy on me again. After I couldn't get the valve to work, I disconnected it again, but the tach is still crazy-jumpy. I can't help but shake the feeling that something somewhere on the board isn't soldered correctly. My kingdom for a copy of the original 2.2 PCB MS2Extra assembly manual...
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