1998 XJ; Slow/Underpowered Acceleration, Shift Problems, Error Codes P0700 & P0720

[j0n4hxj]

Hello!

Thanks for reading, new here, acquired my XJ about this time last year. When I first bought it, I was told I would need new shift solenoids. Against better judgement, I bought a cheaper pack on eBay for about 121 for all 3. Mostly, the shifting wonkyness was from 2nd to 3rd gear, I'd guess. It was also throwing a P0700 code, transmission control system. Anyway, I replaced the solenoids, and it seemed to be okay for a couple days, code was gone, but it shortly returned to its symptoms of late shifting. I never bring it above 3000 RPM, it's always seemed a little underpowered since I bought it, and I feel like I'd blow a gasket to even try it.

That was about 4 or 5 months ago but, lately I've been noticing that it'll slip out of gear around the same shift area (2nd, 3rd). It'll pop right back in, and it's never really a rough slip, but I've got some error codes again. I first got the P0720 OSS Circuit, which would come & go, but today I've got the 'ol P0700 too! I'm hoping it isn't the solenoids, and from reading the forums, would these symptoms be in alignment with a dirty/gummed NSS?

My next mission, before I buy a new OSS, would be to remove, disassemble, clean, then reinstall the NSS to see if that helps. Then I was going to clean the throttle body, & IAC valve.

Any other simple tips/fixes you guys would recommend before biting the bullet on this OSS?

Thanks in advance!