[NEED HELP] Car Jerks/Low speeds (-55)

[Poll Element]

Hi guys,
I've been struggling to get my 91' S13 up to standards. My issue at the moment is that I can't get the car to drive on the highway. It refuses to go past 55 mph. Going down hill I'm lucky enough to get 65 mph but the car starts jerking at this point. I recently took it to the shop to get the transmission looked at and the mech said there was a issue where the car wasn't going past 1st gear/shifting out of 1st was because it was because the throttle was seize in an open position or something. Now that I got that fixed I'm stuck with this situation.

It was suggested to me that it was my fuel pump but I replaced the original pump with the one from my 93' and I never had issues with it before. So to speak the car feel as if it's not getting enough fuel. Like it's choking because the lack of fuel.

Would the issue be my pump or fuel lines?

I must say the original owner said the car had been sitting for about 7 years.
Also at times when I rev the car in neutral it loses pressure even with the pedal down. When I get the chance I'll post a video.

[PapaSmurf2k3]

If it sat for 7 years, there's a decent change a bunch of crud built up in your tank/lines, and now its all in the fuel filter, starving the engine of fuel. Have you tried replacing the filter or checking the lines for flow?
Also check to make sure your engine grounds aren't corroded. There should be one at the back of the head, above the exhaust manifold. It goes to your firewall.

[Poll Element]

Thanks for the advice. I switch the filter which helped a little. My much said it seems like its the pump. I'm going to work on that today to see how that plays out.

[centralcoaster33]

Does the hesitation happen at specific RPMs? I had something similar and it was my transmission posistion switch sensors being incorrect. In my case, 5th was swapped with Neutral iirc. So it was applying the top speed limiter to all gears. Somewhere around 3500-4000 maybe? I forget exactly, it was a while and 2 240's ago. REading your descriptions I suspect this is not your issue, but... maybe it is! Good luck and be sure to post back what your sollution was for others who lurk and search.

[Topless_S13]

Being that it sat for so long, fuel delivery could be the culprit. I suggest cleaning your fuel tank, if not replacing it all together. Gas breaks down after time and can cause a lot of headaches. Check fuel pressure as well.