Misfire / Jerking going uphill

I have a 92 (3.3L) New Yorker 5th Avenue that has makes the car jerk badly going uphill and occasionally makes a backfire / misfire noise. It is a general jerking, not localized (right / left front) by feel. It starts ok and runs smoothly at idle but once you put it in drive and start acceleration, it begins to jerk. It has over 200k mi. I have had the fuel filter replaced, new plugs and plugwires put on. Mechanics have ran codes on the engine and transmission and tell me that no bad codes show up. Any thoughts, suggestions? I’m getting desperate about getting it fixed. Thanks.

A '92 doesn;t have the comprehensive onboard diagnostics system that the newer cars have. It’ll take someone hands-on with a fuel pressure gage, a compression tester, a vacuum gage, a multimeter, and perhaps an engine analyzer with a scope to determine exactly what’s causing the problem.

I’d start by checking the fuel pump pressure at the line. But that’s just a starting point. You need a better shop.

You might have a fuel flow issue instead of a fuel pressure issue, and that is much harder to find, but the result is the same, you will need a new fuel pump. It could be something else too, this could be hard to find.

Maybe I could be repeating after others in this thread, but there could be 3 possible reasons why your car is jerking:

  1. Electric issue where the fuel management system is shutting down
  2. Bad Fuel Pump
  3. Vacuum Leak

For your car, the codes don’t specifically tell you what’s going but only gives you a “general” direction of where to start checking.

Both a compression and an intake manifold vacuum test would be a good place to start. But before you invest in those tests, be sure to bring all the owner’s manual suggested routine maintenance up to date. If everything is already up to date, and te ignition system tests out ok, an air/fuel mixture problem or an exhaust restriction would be my first guess.

Thanks to all of you for the suggestions. My mechanic finally was able to diagnose the problem. The actual problem was age, oil and wiring permeablity. The oil had leaked over the wiring and many of the wires were rotting and shorting out on the block. The mechanic said he would replace one or a section and a wire next to it would crumble. The resolution (if newer car) would have been to replace the wiring harness. The final resolution was to send the car to the knackers (recycle it). Please consider the problem fixed.