My 97 xj with 4.0 began to take longer cranking times to start and increasing roughness while running. As one got worse so did the other. Today it took almost 15 seconds cranking to start. So dropped the tank and changed the fuel pressure regulator/filter and presto starts right up everytime. Problem is the thing still is rough. And can get really rough at 55 and up. I am must wondering if it is a fuel pump issue or fuel injector issue. I have recently replaced plugs, coil, wires, cap, and rotor button. If it is electrical it is pcm. I am stumped though as the scan tool doesn't show anything and the data stream is clean. HELP

side note: if replacing injectors are there oversized units available?

Patrick
Swamp's Diesel

 

What is the condition of your fuel filter?

DO not go with larger injectors. Larger isn't always better.
The fuel injector system was designed to run at a specified pressure and flow-rate. Going over this will only make your problems worse.
The only thing you will gain is a higher fuel cost.

 

The fuel filter is enclosed in the fuel pressure regulator assembly which is what I just replace. This fixed the extended crank issue. It feels like slight stutter that I can compare to scored plunger and barrells in 7.3 powerstroke injectors. The 19lbs injectors from Ford that fit have been tuned successfully by Dennis at TS Performance who is a good friend. I just want to make sure it is not a cam sensor or crank sensor acting up