JRober91

Hello all, so I'm having a heck of a time with my 1991 pickup, 22re engine, manual transmission and I'm just making stabs in the dark now and need some input. So back in the end of may I went home from college for a week and while I was home I changed out my rear differential for a good one, same gears etc, my old one had a blown pinion bearing that was gotten so hot it was seized inside the housing, anyways the new one was solid, ran great, no more whining noise from the rear end when decelerating or coasting. Then I drove back up to college and on the way I noticed that when I got to about 70 mph the engine would "jump" a little and the check engine light flashed for less than a second, so no biggy I thought and just kept going at 65 with no issues. Well over the last two months it has gotten increasingly worse and now it's to the point where the truck is not drive able over 55 mph and the top of the rpm range when shifting up. Basically I'll be increasing speed and right as I'm about to shift the check engine light will flash and it feels like the computer is cutting the gas flow, or it's misfiring or something and the truck bucks and if you keep trying to accelerate it just keeps bucking and won't pick up speed. I could handle this if it was just between shifting but the fact that I can't even go over 55 mph on the highway is very annoying, can't go around anybody etc etc. It will literally get to 55 and then if you even touch the gas the CEL blinks and the engine does it's sputter/jump/misfire thing. I went down a hill and the truck got up to about 60-65 and if I pressed on the gas at all the CEL light went off. I've pulled the codes repeatedly and there is nothing which is the worst part in trying to figure this out. It also seems to happen on certain bumps in the road like if the truck hits several off centered bumps in a row and shakes the truck from side to side the CEL flashes, noticed this when I was coming down a dirt road that was wash boarded out and was just idling. So in the last week I've replaced the distributor cap and rotor, what I assume was a 20 year old fuel filter (it was bad haha), tried running it with the TPS disconnected with no change, and googled for hours trying to find a similar case and no such luck. I have no idea if the rear differential change is related in any way, it was just very close together that this problem started so figured I'd mention it. Maybe I should replace the plug wires? I really hate to keep throwing money at it replacing one part at a time and the toyota dealership is backed up 2 weeks and it's 100$+ just for a diagnostic. I've done all the work on my truck (replaced engine, half axles, rear diff, etc etc) and I hate paying a shop money for something that I could already tell on my own. Thanks for the help and let me know if you need any more information etc!

JRober91

Replaced the plug wires today and no change, been running injector cleaner too but still can't get over 55, starts bucking and surging and CEL flashing