I've got a 99 Miata. It has been a strong running but I decided to go MS to try and get some more umph out of it.

Installed the MSPNP this morning, that was easy enough, and the car fired up on the basemap. It bogs pretty heavy, even dies, when revving in the garage, but I am guessing that's a tuning issue.

Installed the Innovative MTX-L wideband afterwards. I removed the stock O2 sensor and used that bung for the install. I wired the yellow analog output to the stock O2 wiring. Calibrated the MTX-L. Then updated the project to a wideband O2, recalibrated AFR, and set EGO to single wideband per this page: MegaSquirtPNP by DIYAutoTune.com

The Innovative gauge seems to be working. I get a nice steady reading at idle of about 11.8 (no idea if that is right or wrong). The problem is that the MSPNP doesn't seem to be getting the proper signal; it's not steady, either, but completely erratic.

I have found a few other threads with similar issues but haven't found a solution. I'd love to get any thoughts. I'm attaching my msq and a datalog, though I'm not sure how useful that will be.

robert

 

Idle after warmup should be 14.7.
11.8 is full throttle like 12 psi 2560 boost potential.

 

Hah, I figured that might be the case. At this point, I'm more interested in the gauge and CPU agreeing with each other than the actual number.

It is probably worth noting that I did run the programmer for the MTX-L unit and confirmed the settings. I also measured voltage at the factory O2 connector and it was nice and steady, around 2.3x volts if I remember correctly.

The only thing that I know I haven't done "right" is that I did not ground the MTX-L unit at the ECU. Maybe I'll fix that tomorrow, but my understanding is that may skew the reading but shouldn't cause what I am seeing.

Other people seem to have had luck wiring into the option port. I don't really want to do that, but I might try it tomorrow to see what happens.

Thanks again,

robert

 

An erratic signal could definitely be a ground issue. Analog signals are a lot more prone to ground interference than digital signals. Ground to the correct location then report back.

 

This morning I ran ground to pin 22 and O2 signal to pin 21. Seems like it is working now. I probably should have done the ground first just to learn if that was the problem, but I didn't feel like getting under the dash twice.

robert