Engine Cut-Out at Speed???

HELP!
Daily driver, 2000 XJ, 4.0, stock engine except for replacement Tupy head off of a Wrangler. A little over 200,000 miles on lower engine and tranny.
XJ has Cruise Control, Stock AW4 Tranny, NP231 Transfer, OME Lift. Pretty normal Jeep. I take care of it well, it is my daily driver, and I have no intention of getting rid of it. So this problem is a big deal for me.

***For the last 6 months, and slowly getting worse, at speed, on the Interstate, usually while using Cruise (at 80mph) or coming down the mountain at 80, with the jeep resting against the throttle/tranny downhill.....I get this sudden "cutout" of the engine. The RPM's drop for just a second, and for just a split second it feels like the drive train has just completely turned-off or disengaged. But only for a split second. Possibly even less than a second.
If I hit the gas it takes off like nothing happened. If I am in Cruise, and I do nothing, it jerks, lunges forward for a split second in total death-mode, and then resumes running perfectly fine a half-second later. When this happens, there is no disruption to power. Dash and radio do not cutout. Cruise does not cutout. It just feels like the engine has been turned off, for about half of a second.

I have a code-reader and am getting no codes. Temps of everything are fine. Fluids are all in spec, and factory recommended, except the Royal Purple in my Transfer Case which is also new and filled to spec. It feels a bit like a misfire or a dropped cylinder. Or maybe if all the cylinders didn't get spark for a split second. Ignition Rail is a NAPA echlin from a couple of years ago. I still have my OEM one and I think it is good. Plugs are all Champion, factory recommended. Throttle and Intake sensors have all been replaced in the last few years. Mopar intake cleaner has been sprayed into throttle body two summers ago. Every button and switch in my Jeep works. I keep it that way. So I need to figure this out.

I have no idea where to go here. I am pretty handy with my Jeep and not afraid to dig in with wrenches. But I have no idea what is happening here. It is obviously disconcerting to have my Jeep just completely stop running for a half second , several times per commuite. I commute 32 miles on the Interstate each way at 80mph, flat-out. This drive train cut out happens 2-4 times per trip. Each time I fear will be the time that I have to pull to the shoulder. I need to fix this for peace of mind. Anyone have any suggestions?

Thanks,

JG

Since you still have your OE ignition rail I would swap that one in and see if anything changes. That seems like a simple first step since there is no need to spend any money.

I don't know how the wiring works that feeds that rail, but I would pursue a wiring diagram and start checking out the various components that relate to it, including ground connections.

Has the crank sensor ever been replaced?

TPS is another possibility.

Use Mopar sensors and coils.

Personally it sounds like a tranny problem.

Crank sensor and TPS have been replaced.
How would I test tranny to know?

Thanks,

JG

If it was a tranny issue (and it may be), would the RPMs drop out? Because the RPM gauge drops out for just a split second, then everything picks up and runs normal again.
This seems to occur less when it is cool outside.

JG

The most common and most likely cause is the CPS. If the CPS is genuine Jeep, and tests good, suspect the O2 sensors.

tn_outside2003 said:

Crank sensor and TPS have been replaced.

Click to expand...

Did you install genuine Jeep sensors ?

Most auto parts stores sell cheap crappy Chinese made parts, some that even come with a "Lifetime Warranty". These parts are poorly manufactured and/or made from inferior materials. They are often out of specification, or even failed, right out of the box. The ones that are not faulty many times will have a short service life before they fail. Always buy top quality replacement parts and genuine Jeep engine sensors. Numerous threads detail long and frustrating searches for a "problem" that ended up being cured simply with genuine Jeep repair parts.

Cheap parts are cheap for a reason.

I decided that I am not sure if we are talking about the cam position sensor that determines spark (replaced about 10 months ago with Mopar part from dealer) or the crank position sensor, replaced with O'Reilly garbage about two or three years ago.

I have had increasing problems with discount auto parts, regardless of car or part. However, cam position sensor is a magnet and a spinning shaft. Crank sensor is a piece of flat bar with a magnet and two bolt holes. Hard to imagine how jeep (or anyone) improves on this. But they may. I am happy to be informed. I just had a dorman crank pulley be junk out of the box and had to be replaced with a honda oem part....just because. One worked, one didn't. And it is just a pulley.

Throttle position sensor is from scrapyard off of an OEM jeep. I have the original. Both work the same so I don't think either is bad.