Ok, this is probably one of the screwiest issues Ive come across in my 20+ years of working on cars. The strangest part is this all started with a simple break job and Fuel pump change for the sending unit failure! After I finished with the breaks the damn ignition module died. This is the 2nd or 3rd one Ive replaced in the past 5 years Ive had this truck. (2000 2wd 2 door) After I replaced the ICM I found the truck feels like it lost all power and now it feels like the tranny is slipping/not shifting correctly. First I checked the fuel pressure as I thought it might be starving for fuel under load, I found the pressure to be low (55psi) so I isolated it to the pressure regulator. I replaced the FPR and pressure was back up to spec. Did a test drive and had same issues. I thought maybe the catalytic converter might be clogged and creating to much back pressure even though I haven't noticed any rotten egg smells. I just got done hitting the cat with my fist and it does have some rattles in it. Is it possible this could be causing my issues? Thanks in advance!

 

If you are good with muffler clamps,slice before the cat and start it up for a min and see how it runs. the downstream sensor will flip the service light,and it might run a wee bit different,but if the cats clogged,it'll run better cut anyways.

 

I have a thread "4L60e 700R4 things I've learned" I list almost every sensor and basics on how it relates to transmission operation. Check that out and see if any of that sounds like it might help. Things like TPS(throttle position) affects shift points as well as fuel enrichment used for rapid throttle changes. MAP(manifold pressure) i.e. vacuum adjusts line pressure as well as adding/removing fuel depending on how much vacuum the engine is pulling.

 

Sweet! That thread rocks! Now I just gotta figure out why the reverse lights are coming on whenever it's in gear and I hold the brake pedal down... I'm to the point where I just want to crush this biotch! Just found the thread on that problem. Think I might have screwed up the wires when I was messing with the fuel tank. Any one know what the connector with the blue cap is hanging behind the tank under the rear bumper is for?