Spike117

So I've been struggling with getting my car to fire up on my DIYPNP for a good 6 months now with no progress whatsoever. My car is a 96 with AEM wideband and GM IAT sensor installed, car has a 2mm overbore (1949 cc), a BP4W head and toyota COPs. I have a 36-2 trigger wheel with 99 trigger sensor installed, but I'm not sure I installed the trigger wheel in the correct orientation or if my wiring for the VR sensor is correct. For that reason I've been trying to get the car to start using the 4G63 trigger settings. I have verified multiple times that my jumpers are wired correctly.

I am able to get the coils to fire when in test mode just fine, but get no spark when cranking (confirmed by hanging timing light over the windshield while cranking).

I've also noticed a fun issue where if I have the IAC "run valve before start" my voltage reading in tuner studio bounces all over the place.

I also have an issue that I get the error "Conflict between spare output ports and spark outputs" randomly after power cycling the megasquirt unit. When I get this unit my cooling fan kicks on, my coils start firing and my tac on tunerstudio goes all the way up. I have been unable to fix this error other than reflashing the firmware after which I get about 3-5 power cycles before I get this error again.

I'm about at wits end with this thing as I've been trying every possible solution i've been able to find online for 6 months now and still have only gotten the car to fire for a few times, and never maintain an idle.

Will post logs and copy of tune in next post.

Spike117

Quick composite log and copy of current tune

venetox

For the Voltage reading bouncing around when run valve before start is enabled.
Install a Flyback Diode (Diode in parallel with your Idle Motor but with reversed polarity).

See if that resolved the other issues too. (Don't have any software to view the logs at work)

Spike117

Should I do this on the pull up area of the board or just on the line to the IAC?

venetox

I did mine in the wires, you probably should do it up near the IAC so that you don't have any weird ground loops.

Also make sure all your sensors go to one separate ground wire that is not hooked up anywhere else.
On DIYPNP it shouldn't really matter but can help, that is a separate thing to this issue though.

Spike117

HOLY **** THIS WAS IT! 6 months of fighting the damn thing.

venetox

😀😀😀 glad it fixed it, always wondered why our idle sucked but never looked into it for ages because car wasnt finished