Hesitate on acceleration-Success
 

My daughter has a 2000 jeep grand cherokee. Occasionally, she gets a lack of power, and it may stall. The codes are p0118,p0300 ,p0303 and p0306. I changed fuel filter, added two bottles of dry gas. No change. When it does stall, she can start it right back up, and it seems to happen sporadically. Any ideas? My next plan is to get a fuel pressure reading at the fuel rail. I guess it could be spark though.
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Here is what happened. Hope it helps someone in the future. Both pins on the connector of the engine coolant temp sensor weren't makng good contact. As things heated up, I saw voltage variations. I finally got the pins out, munched them down a little, and after a little time and persuasion, got the connector connected again. No more temp fluctuations, and hopefully no more stalling. I went for a 20 mile ride no problem. After the fix, the voltage on the ground side of the sensor was reading about 3.4 volts cold and would drop to .93 or so when hot when the gauge showed 210. Voltage trended smoothly down as it heated, and up a smidgeon briefly when the tstat opened and cooled slightly, but no big swing in voltage.
Here's what else I learned. I bought a new cam position sensor and crank position sensor and a new temp sensor. Probably $130 of parts I didn't really need. I saw the big temp swing, should have put that together with the poor run/stall at idle as the computer reacted to the seemingly low temp. Anyway I'm a happy man now, and hope someone may benefit from my experience.

I was wondering about the engine coolant temp sensor, but it seems to run fine other than the random lack of power and stalling. Unfortunately the vehicle is 3 hours away now.

Had a similar problem on my '03 WJ , turned out to be the throttle position sensor. I went ahead and bought the expensive USA made OEM dealer part as I found the after market ones to be sub par.

Three codes for misfires. When was the last time a tune up was done?

Ghack,
I recently had a similar problem with my 97 GC with 4.0L I6. It was studdering (not stalling) at around 1000 rpm when starting from a stop. Ran fine @ highway speeds. Some research and tinkering and the culprit was the throttle position sensor. With the new sensor in place the problem was somewhat better but not solved. Additional tinkering and the TPS connector was found to be intermittent. New connector solved the problem at the low RPM. Still slight studder @ 1200 to 1500 RPM. Scan showed O2 sensors somewhat erratic. Replaced both and problem was better but not completely cured. Replaced the camshaft sensor and new distributor cap and rotor. Engine runs like new. The GC has 18 years and 160K miles so it seems that the sensors can drift and vibration wears on the connectors so, depending on the miles on your 2000 GC and how you want approach the problem I would start with the TPS first.

There are several videos on youtube to show you how to check the TPS with a volt, ohm meter.

Good luck,
Khawk

Thanks Guys, now she says when it hesitates, she's usually in traffic, and finds it more effective to turn it off and then on again. Cranks a bit, then starts and she's on her way. She's coming home this weekend, so i'll test fuel pump pressure and do checks on the TPS. Maybe throw some new plugs/wires in, which it probably needs, though i don't think that's causing the stalling/hesitation. It just seems so random, driving along and it stalls, not just on acceleration. Sometimes it goes a couple days no problems.

Checked pump pressure this morning, it's running a pretty steady 55psi. Tried wiggling PCM wires and tps wires, but no issues there when I did that. It seems to run fine normally , gas mileage is fine 18 mpg or so. I keep thinking it might be water in fuel, issue is only temporary. I watched video on testing tps, I can try that. Maybe injector/fuel system cleaner.

You know you're a Jeep owner when you say 18mpg is good.

@ Bustedback.... LOL!!!

I'm only getting 15-16 right now and putting the 32's on this coming week. that may bring it down a couple more. Guess I'll see.

It will, and possibly make the engine run a little hotter. It did for me.

Might not be too bad I have 31's on right now. Doesn't run hot. I went to a wider wheel and was told I run the risk of breaking the bead if I air down to go wheeling. Where in the desert do you not air down to go wheeling, (unless you want to get stuck)? Got a few more opinions on that, and the majority was that there is a risk. I need to get more aggressive tires anyway. Currently running Pirelli Scorpion A/T, not that great for off road.

sorry, i hijacked the thread i'm done.

Around town and on flat ground the 32's work fine, but once I hit the hills my temps climb a little and it's a sluggish turd. I'm planning on regearing some day because 3.55's and 32's make the 4.0 work pretty hard. The two row all aluminum and electric cooling fan have helped quite a bit though.

stilll struggling
 

Still having issues. Definitely a lower rpm issue. i have a spare motor which ran fine until a rod pushed out through the oil pan. i took from that the iac and tps. I also replaced from o'reillys, the crank sensor and cam sensor. Replaced plugs, fuel pressure is fine at rail, right around 55psi. I'm not sure about the coil pack, don't have a good test for that. i have the coolant sensor on order. The temp does seem to be erratic. The gauge shows barely off the low end even when it's been running for a while. Sometimes it's up close to 200. The issue's remain. It can start and run fine, but sometimes as rpm drops, it stalls. We had a really hot day, the car sat for an hour, and wouldn't start. i can usually get it started by flooring the pedal and cranking. it starts reluctantly, and as it gets up to 3000 rpm, i back off a little, too low and it will stall again. i've pretty much exhausted my ideas. Hoping the coolant sensor helps. I also wonder about the mass air flow sensor, i can change that from the spare motor. You guys have any ideas?