'94 with basic boltons and MS3X - can't get running right - Miata Turbo Forum - Boost cars, acquire cats.

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Old 10-16-2013, 10:53 AM   #1
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Default '94 with basic boltons and MS3X - can't get running right

Hi guys.

Car is a '94 with I/H/E and a braineack MS3X. Running AEM Wideband. Car ran fine on stock ECU before the MS was installed, and runs fine if the stock unit is swapped back in.

So...install went smoothly, but having trouble getting the car to run.

It starts up fine, but idles around 2 or 300. If it doesn't die within a few seconds, it will slowly settle up to a normal 850 idle, but if I so much as touch the throttle, as soon as the revs fall back down to idle, the car will stumble horribly and often die.

Also, can't get TPS calibration to work at all. Always reads zero whether at closed or wide open throttle.

When I take the car for a spin around the block, it will drive okay at very light throttle input, but anything more and it will sputter and stumble. Of course if I let revs fall back to idle, it will idle extremely low, sputter and often die.

There is also a very strange loud whining/humming noise that is not present when the stock ecu is swapped back in. It seems only to occur at idle, and then mostly when the car is idling at the normal 850rpm. When driving around it disappears. Is this IAC maybe?

Using the base map provided by braineack. haven't fooled around with any settings beyond the set-up steps listed in his instructions. Can't for the life of me figure out where to begin or what exactly is wrong.

Really really appreciate any help anyone is able to give.
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Old 10-16-2013, 11:26 AM   #2
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I'll post the msq momentarily, and I'll grab a datalog within the next hour or two.


edit: msq
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File Type: msq 2013-10-16_10.27.19.msq (177.4 KB, 132 views)
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Old 10-16-2013, 11:41 AM   #3
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Just to verify the TPS issue, when you turn the ignition to "on" and go to Tools/Calibrate TPS in Tunerstudio, if you press the throttle the voltage reading stays at zero? Did you verify that the TPS is plugged in?
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Old 10-16-2013, 11:44 AM   #4
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see email.
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Old 10-16-2013, 11:45 AM   #5
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Thanks man. I'll check it out.
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Old 10-18-2013, 04:13 PM   #6
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update for people in the future who have similar problems:

The whining/humming noise at idle was improper frequency on the IAC. Setting was close to 200(hz? MHz?) which is the setting for a 1.6, when it should have been at close to 400 for a 1.8.



As far as the crappy idle and running, my TPS was not getting 5v from the top light-green/white wire.

I tested the continuity on the megasquirt harness for the gray wire on pin 26 of the megasquirt side mainboard plug. It tested fine, so I pulled the ecu case apart and looked at the mainboard. Following the schematics for pin 26, I checked out every potential problem area.

Problem ended up being fuse F2 on the mainboard...it's literally right up against the middle of the DB37 connector One end was soldered into its hole, but the other apparently was not soldered. I soldered it up (first time soldering EVER! Did a pretty good job considering. I was scared id **** it up :-D)

Anyway, boxed it back up and plugged in the harness, turned the key on, and checked the voltage top wire (5VREF, lt. green/white stripe) on the TPS connector with my multimeter. Sure enough, I had the required 5V passing through, instead of the ~0.02 mV I had before :P.

So I hopped in, plugged in the laptop, and calibrated the TPS. This time it worked great instead of reading at zero for both closed and wide open throttle.

I started her up, adjusted the idle screw a bit, and went off for a test drive! Finally driving normally, exactly as it should.

She's officially a squirter now LOLOLOLZ
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