ECMlink Switch from closed to open loop causing misfire

[steve]

When you install the PTU on the metal mounting plate, clean the plate and if you have some thermal paste (from like a computer CPU install) use that between the two. The plate is both a mounting bracket and a heatsink for the PTU.

 

[We're on Boost]

Thank you and apologies I meant to say the RPM needle was jumping not the speedometer. W're getting down to the last few options here and I know we're close (with the CPS being the last option since it's pretty deep in there). Since I didn't need the metal plate I ordered a HERKO HLX061 PTU replacement. Oddly enough when I spoke with my friend (Mechanic who sold me the car) he said that he switched out PTU's and it never changed anything. We're down to injector wiring and testing resistance from plug to ECU, or sending the ECU in for repair (which he also mentioned that it was sent in once before...)

Sounds like the right ideas there. I was going to ask if you meant the tach rather than the speedometer
The Herko, I don't know, it might be ok but don't throw your old one away!
I looked for customer reviews of the HERKO HLX061 on some sites that sell it - Amazon, Walmart, Ebay. Found 0 reviews on Amazon, 0 on Walmart, and 1 product rating on Ebay. The Ebay rating was eerily familiar:
"Works but it is flawed. I tried this part on an all original 97 eclipse gsx and it did not work perfectly. My speedometer and rpm gauge jumped around inaccurately, however my car did run with the part installed. It also comes with thermal paste FYI"

Well we don't know what else was wrong with his car. But don't throw the old one away
I thought for a sec it might have been you that posted the review, but it says it was posted in 2019.

Yeah the crank position sensor will be a little bit of a project to get at.

Thanks for this recommendation! I'm willing to try anything, so I'll give this a shot today and report back

This is such an interesting possibility.

I'm not clear about how noticeable the misfire is in your case. If it is noticeable, do you notice it long before the trouble code shows up? Or does it all of a sudden start to be noticeable and then a few seconds later the code shows up? Or what?

What is your spark plug gap?