RememberTheMallamo

I have a 1993 XJ sport, 4.0L 5-speed 4x4 with 89,000 miles. It had a tuneup around 85,000 miles, new plugs, wires, etc. Oil has been changed twice since then.

It seems to hesitate sometimes, I push down on the gas pedal and get little to no response. It feels like a chugging or lurching power delivery. It stops after a few seconds and then feels normal. Sometimes a downshift or simply pulling it out of gear and putting it back in solve it. Typically only happens below 3,000RPM.

Possible ideas:
1. Does this engine just have no power and want to stall so easily at low RPMs like 1500-2000? I drive a manual, I obviously know what a stalling engine feels like lol! It just doesn't feel like a regular stall out happening.
2. Clutch plates sticking? My Mazda's clutch went out but it wouldn't chug it would just rev higher than normal like it was partially engaged, the Jeep feels different.
3. Fuel filter clogged/worn out
4. Fuel pump relay.
5. Throttle body needs cleaning or something?

So guys, my knowledge is limited, advise me where to start!

1976Mustang

I would check the O2 sensor too. Er, i think that's the one i'm thinking of...
Also, 89k miles? Holy crap that's a baby! I'm over 200k and still running strong. Good find!

ZINGGG

I'd change the fuel filter out for good measure. Might want to test for good fuel pressure too.

How fast are you going usually when this hesitation happens?

I'd agree that it could be a dying o2 sensor

freegdr

Id check for stored codes first that why the system allows this to be done...

Radi

While you're under the hood check the TPS. You'll need a DVM to measure the output voltage while operating the throttle by hand.
If TPS isn't working right fuel delivery will be slow to catch up when you open the throttle, sort of like driving a carb'd car with no accelerator pump.

salad

Holy cow, at 89k everything should be brand new except for what the mice have eaten!

Agreed on the TPS being suspect. Putting it in/out of gear means you're letting up on the accelerator. Clean the crap outta the throttle body and measure the output voltage with an analog multimeter. The signal coming out of the thing should be a SMOOTH sweep from approx 0 volts to 4 or 4.5 (FSM for the 1999 XJ specifies 4.5, but apparently the Renix system peaks at 3.5 or 4, so no idea what a 93 would have). If you can't backprobe it you can test it with the vehicle off (or just feed 5V into it from a pile of batteries or something) by measuring the resistance between input and output pins. You should see almost infinite resistance with the throttle shut and a smooth drop as it opens up. Some electrical contact cleaner may tackle any good that could've gotten in there but once a pot is toast it's toast

RememberTheMallamo

I'm unfamiliar with all these acronyms... TPS is throttle position sensor? What's a DVM? How do I test voltage on any of what you've said? I think I'm gonna have to start some research.

And the speed at which the hesitation occurs is anything from 15mph around town to 70mph on the interstate.

RTorrez1

TPS is throttle position sensor? CORRECT.
What's a DVM? DIGITAL VOLTAGE METER.

RememberTheMallamo

Picked up some parts at Autozone the other day. Got a new fuel filter because why not? Got a TPS which I think is the problem. The guy talked me into an O2 sensor as well (he gave me some free Lucas Oil cleaner stuff and 10% off everything). I'm going to install the TPS first and drive around to see if it fixed the problem. If not I'll put the O2 sensor on after. I'll update here with my results.

F1Addict

While you're in there, check your spark plug wires. You said they were just replaced at 85K but one of them might not have snapped all the way on.

rrich

Either TPS or -- more likely - loose or defective coil wire - swap it wth a known good one.

RememberTheMallamo

I'm very unfamiliar with plugs and wires. I'll try to find some Youtube how-to videos or something.