91 Jeep Grand Cherokee Stutters like Porky Pig



My 1991 Jeep Grand Cherokee, 4.0L V-6 has a particular problem when it has warmed up and has been shifting through the gears. (Automatic Transmission) This Jeep begins to stutter worse than Porky Pig, like it’s not getting enough gas or air. We have replaced both the Air Filter and Fuel Filter, yet the problem persists. I have cleaned the plugs and gapped them. Distributor is okay. Running out of options before hauling it to a mechanic I can’t afford


Mel Blanc, reincarnated. I wondered how he’d come back.


When does the engine begin to “stutter” (misfire)? Is it during acceleration? Is it during idle, or coast down?
Missing sparks, or erratic fuel injectors, can cause misfire.
Have you changed the spark plug wires? The ignition coil? Have you measured the fuel pressure with the engine under load (in DRIVE at 1500 rpm, foot on the brake; or, while accelerating).
Auto parts stores have fuel injector test lights to see if the fuel injectors are getting a signal. Ask for a: 'NOID test light.


During acceleration. Generally if we do the acceleration slow enough on flat land it’ll work, but if we try to kick it into passing gear, it’ll start to misfire and sputter. As we get paid tomorrow I’m going to redo the sparkplug wires and plugs completely. Ignition coil should be okay, we just put in a new starter recently…Or am I revealing how un-mechanical I am with that statement?


we just put in a new starter recently…Or am I revealing how un-mechanical I am with that statement?Well, yes, actually.

Since you’ve already replaced the fuel filter, I would check the fuel pressure. The fuel pump might be failing, leading to fuel starvation. The other possibility is a clogged catalytic converter.


By the way, your engine is a straight 6, not a V6.


Usually stuttering while accelerating means fuel starvation.


What does “redo the spark plugs and wires” mean? Spark plugs should be replaced, not “cleaned”. If the spark plugs wires are several years old, they may be the cause of misfire, also. Are the distributor cap and rotor nearly new? Is that why they are “okay”?
Measuring fuel pressure isn’t that hard. A gauge is fairly cheap. The 'NOID fuel injector test lights are about $7 each. One 'NOID would be enough (minimum).
Generally, an engine which misfires during acceleration, under load (weight, or hill climbing), and at higher speed, is caused by weak spark, and or too little fuel being sprayed into the engine.


Have you had it scanned for codes? Advanced Auto & Auto Zone will scan for free. Advanced scanned my car 2 wks ago because of a CEL and he printed out the code & brief explanation.