89 cherokee jerking while cruising on highway

[Zac ravioli]

My stock 1989 Jeep Cherokee 4.0 with a 4speed automatic has been doing a rapid jerking/nudging while its maintaining speed only happens above 55mph and I have been trying to figure it out since I got it about a year ago. Rpm and gear doesn't affect it as long as im going above 55 the engine also sounds like its running at a consistent rpm. Ste strange part is once out of every 50 times I get on the highway it doesn't do it the entire time but I didn't do anything different

 

[Goose_XJ88]

What have you done to try and fix it?
Try cleaning your throttle body, clean the IAT sensor, adjust your TPS.

I had bad surging and backfire on my 88 a while back going freeway speeds and a certain throttle input. Unfortunately I dont recall what fixed my issue.

 

[Zac ravioli]

Ive tested and adjusted the tps, cleaned the throttle body, replaced the iac valve, egr valve, crank sensor, o2 sensor, spark plugs, ignition coil, spark plug wires, most of the vacuum lines, and the fuel injectors. most of the things I've listened aren't directly trying to solve the issue but its still weird that after all that it still won't go away

 

[Anak]

Could it be a driveline issue?

Remove the front driveshaft and see if that changes anything.

 

[Zac ravioli]

update: since I put in the new vacuum lines and adjusted the tps its gotten worse but its also changed now the problem is happening when i cruse at 45-50mph and its making the car hop makes me think there's some sort of transition or computer issue

 

[lawsoncl]

Is it perhaps the torque converter locking and unlocking? Does it stop if you lift the brake pedal up or lightly press with your foot? That would point to the white switch high up on the brake pedal being misadjusted or dirty. As cruising speed, lightly tapping the brake pedal should trigger the trans computer to unlock the torque converter and the rpm should jump a few hundred rpm.