thesteve

I just installed my MM0105 MSPNP Pro ECU and everything seems to be working out of the box except for the idle valve. I'm seeing about 8v (open circuit) at the IAC connector and about 0v with any load (1k resistor or IAC). The engine runs great and will run smoothly at idle speeds (~1000RPM) as long as you modulate the RPM with the gas pedal. As soon as I lift off the engine dies. As far as I can tell, the MS is not sending any actual power to the IAC.

Is there anything that needs to be modified to get the IAC working? Settings or a jumper on the board I missed? The IAC audibly moves when jumped directly to 12v, and it idles smoothly on the OEM ECU so I don't think the valve itself is shot.

Car is a 2001 1.8 VVT Miata, all stock except for the Megasquirt itself. I'm using the tune that came with the unit, available here: http://www.megasquirtpnp.com/downloa..._Miata_132.msq

Thanks!

curly

iTrader: (25)

The cars harness should supply 12v on one pin. If not, you have a harness issue.
The MS pulses the ground on the other pin. Go to test mode and turn the idle output on. If there's not continuity to ground, you either have a different harness issue or a MS issue.

thesteve

Thanks! I was testing pin to pin. I'll run outside and verify the voltage now.

thesteve

So the hot pin is showing the full 12V, but the pulsed ground doesn't seem to be working. I'm seeing no continuity to ground on the other pin regardless of IAC percentage, even at 100%. I don't think it's the wiring since it's all stock and it idles with the factory ECU plugged in. I emailed DIYAutoTune as well to see if they had any recommendations, though I don't expect they'll be able to reply until Monday.

Chiburbian

iTrader: (1)

If your stock ecu idled the car this one should too, provided nothing got disconnected or no wires were broken. I am running the same ECU and on the same model year car.

Worse comes to worse you can go into idle valve test mode and up it to 50 and see what happens... if it doesn't idle the car (at like 2,000 rpm plus) then something is wrong wiring wise. I did a side by side comparison of your base tune and mine and nothing looked too out of the ordinary.

thesteve

I posted another reply but it's apparently still waiting to be approved by a mod. I verified that I have 12V on one of the two pins, but the other does not have any continuity to ground no matter what I set the test output to in Tunerstudio. I've tried everything from 0% to 100% and it doesn't change. The MS is not able to move the valve, so it just dies when I take my foot off the pedal even with the test output locked at 100%. Since the OEM ECU works I worry there's something wrong with the MS unit itself.

curly

iTrader: (25)

You want to test in I/O test mode, not idle valve test mode. 100% is still a pulsating ground and there won't be continuity. If you get ground via this method, and the valve works with the stock ecu, id start looking elsewhere, like fueling.

thesteve

Ah I see. I'll give that a try and will report back.

Chiburbian

iTrader: (1)

I meant to try 50% duty on idle valve with it hooked up, engine running, and slowly let off throttle. Curly is far more experienced than I though - so do what he says.

thesteve

Finally had a chance to look at this again. Even in I/O test mode I'm getting no continuity to ground. There's no difference between on and off. I swapped back to the OEM ECU and verified that the idle valve is working. Something must be wrong with the MS unit as far as I can tell. I updated the firmware just in case but saw no change.

thesteve

I checked the wiring on the car itself. The IAC itself is showing about 8.5 ohms, and when I test it all the way through the ECU pins I'm seeing about 9 ohms which makes sense for the wire lengths involved. The MS is absolutely not grounding out the IAC/PWM1 pin when it's set to on. I replaced the IAC with a 1k ohm resistor so I could watch voltages on either side of the load and it's just not switching it. Unless there's a fuse on that PWM output, I'd say that output is dead. Hopefully DIY's support gets back to me soon with a better way to test it.

curly

iTrader: (25)

try another output if you want, even an on/off. Just to make sure the idle valve is working. But yeah, if it's not grounding you have an issue with the MS.

Braineack

iTrader: (62)

no idea why the system flagged that.