XJ broke down on the fwy tonight.

93 XJ Country 4.0L AW4 NP242
My wife was driving my jeep since her car is getting a new timing belt. She was driving on the fwy at 65mph heading up a slight 3 miles grade. Temp, oil press, volts everything were within normal range.

The jeep lost power about half way up the grade and she was able to get over to the side. I was about 30 mins away so I jumped into my car and headed over. I thought it sounded like my cps issue I had over the summer which was replaced. She tried to turn it over and it would not start from what she told me. So I had her wait 15 mins. I called and it idled for a second and she gave it some gas and it shortly stalled. I got there and tried to start it. It would idle rough at around 500rpms and anytime I would give it gas it would pop in the engine bay area and start to miss. Then it would eventually die. I did not visually see anything odd with a flashlight and did not smell anything or see any colored smoke coming from the exhaust.

I ended up getting it towed to my house to check out in the morning.

Start with the basics. Check plugs, wires, injectors, MAP, IAT, etc.

I had a similar issue with one of my 96's. I ended up replacing the ignition coil that was cracked on the back side next to the block. When the col would get hot it would fail and the jeep would stall. When the coil cooled off it would start right up and run fine until the issue repeated itself.

Not saying thats your issue but add the coil to your list of parts to check

Where did you buy your last crank sensor? Reason I am asking is that I have had mixed (poor) luck with aftermarket crank sensors.

So, in my book....the crank sensor is still in play

As well as ignition coil.

I would perform the key-on, key-off technique to see if there are any stored codes that can yield clues.

Then of course, go back to basics. Confirm a strong, blue, snapping spark. Confirm adequate fuel delivery with a fuel pressure gauge, etc.

After you have performed the basic checks as others have recommended; if you have a VOM you should check the TPS.
With the engine OFF remove the connector and measure the resistance across the leads. The resistance should steadily change going up or down depending upon which way you cycle the throttle.
If it indicates an erratic resistance or no change then the TPS contacts are either oxidized or broken.
You can attempt to spray electronic contact cleaner and cycle the TPS in an attempt to clean the contacts; otherwise you will need to replace the TPS.

After some testing and checking this morning. It is either the fuel pressure reg or the fuel pump. I should have these in tomorrow.
Thanks for the replies.

Change that fuel filter too.

Rent a fuel pressure gauge, (auto parts store) and check fuel pressure and how long to drop down after 'engine off'.

Check the old pump assembly for the short connecting hose, inside the assembly, from the pump itself is clamped properly. A few reports of loose clamp/hose now and then leaking off pressure/flow.

New "O" ring for assembly to tank, only a few $ at dealer. Tank does not have to be dropped for fuel pump that year.

Good Luck,
Orange

So I have a bit of an update.

Fuel pump along with filter and top ring seal have been replace. Also the fuel reg has been replaced.

I drove it a bit tonight and notice during normal driving, it drives fine. But if I give it WOT it will hesitat and bog then drive fine.

Is it the correct filter and regulator? Also was the strained replaced?

Yes, as far as I know based off of the part#'s.

The whole fuel pump assembly with screen was replaced.

Could be a flat spot in the TPS. Using an analog meter check the TPS output voltage through its full range of motion. Watch for any "blips" in the needle swing, that would indicate a bad spot in the TPS.

EDIT: try bypassing the ballast resistor for the fuel pump, if you haven't done that already.

joe_peters said:

Could be a flat spot in the TPS. Using an analog meter check the TPS output voltage through its full range of motion. Watch for any "blips" in the needle swing, that would indicate a bad spot in the TPS.

EDIT: try bypassing the ballast resistor for the fuel pump, if you haven't done that already.

Click to expand...

Do you by chance have a link on how to bypass the ballast resistor?
I might just change the TPS since it is a cheap part.

My xj has remained 100% stock engine wise the 4yrs I have owned it.

Simple as plain toast.

On the driver's side fenderwell, white ceramic ballast resistor with two wires attached using spade connectors. Make up a short piece of equal gauge wire with a female spade connector on each end, remove the two wires from the ballast resistor and connect them together with the splice. Option two, use a short piece of equal gauge wire and solder it between the two wires, use heat-shrink tubing or tape it up good.

Photo from lunghd.com:

Thanks!
What does bypassing this do/improve?

ERock62 said:

Thanks!
What does bypassing this do/improve?

Click to expand...

the ballast resistor was put there to drop the pump voltage so it wouldn't be so noisy while cruising down the highway. The early models never had it, my 87 left the factory without, then people started complaining about the noise from the pump and the resistor was put in place to quiet it. Honestly the pump will be happier with full voltage. It is bypassed during start, and at other times depending on throttle position, at least for the Renix system, HO's are a bit different and I cannot speak to modes of operation for the ballast resistor on those.
Regardless you can bypass it to see if it solves your issue, and you can either replace it or leave it bypassed forever depending on how much the pump noise bothers you.

Update.

I went drove about 200 miles friday and sat up to the high desert for NYE. About 50 miles were offroad. XJ ran like a champ and pulled well up the grade going up to the high desert.