Long story short was on the highway today (light snow on roads) driving in 4hi. I was maybe doing 60mph for 5-10min. No issues. Several hours later i took the truck out again and noticed significant bucking and hesitation while trying to get it to 50mph. The harder I hit the gas the worse the bucking and hesitation became (like a bad misfire) so i had to feather it to run smooth; but it would only be smooth under 40ish mph. During hesitation the check engine light did not turn on. What should I be looking at to diagnose? Does it sound like transmission issue? TPS/throttle body? (I just cleaned the throttle body 2 days ago), EGR? Any help is greatly appreciated.

 

What are you driving??

 

Sorry, I should've included in OP. 2005 Ram 1500 5.7

 

Ok, that's just strange..... Might be low fuel pressure, might be a clogged cat.... but, if it was misfiring, I would think the PCM would complain about that...... Do you have a scanner that can read live data? Might wanna have a look at misfire counters, and any pending codes.....

 

I should mention I did have a Cel for a cylinder 7 misfire + fuel injector open circuit a few days ago. I changed cylinder 7 injector + cleaned the throttle body and the Cel never came back. Also, i have had issues with one cat a couple years ago. I was getting a cel related to one so I did the adapter+ steel wool trick to turn it off. It hasn't been an issue since. If the cat was clogged could I notice it by putting my hand over the tailpipe if someone revs the engine? The truck idles fine and sounds normal being reved but when you're driving it and try to give it the beans it bucks and stumbles.
Yesterday, when the issue was happening I was hitting the gas trying to get the cel to turn on but it never did. Im going to go outside and drive it around again in a few. Did a little research and Im hoping its something like EGR valve or TPS (throttle body). I've had this issue for awhile: when accelerating at a steady speed all of a sudden i'll get a suge of power. Like OD is initiated even though my foot hasnt pressed the gas any further.

Also, no live data unfortunately -my scanner sub expired.

 

Bad TPS may explain it as well.... Do you actually have a cable going to the throttle body? Or is it throttle by wire?? (electronic)

 

Still can't get the cel to turn on. Tried unplugging egr and no difference. Tps is electronic - located inside the throttle body.

 

Think yer gonna need a scanner to look at live data while driving.......

 

Definitely leaning towards tps. I disconnected battery + TPS for a minute then did the throttle relearn? (Turn key to on position for 30 seconds then start) And it significantly reduced the bucking and hesitation. I still get a couple bucks around 3rd gear but huge difference. Gonna try a new throttle body. 🤞

 

Might also be the pedal position sensor.......