[BJORN98TJ]

I have a 98 TJ that has been very good to me for many years. I despise going to the dealership for help, but my Jeep has developed a strange new quirk that I can't figure out. When I am driving it around town at speeds under sixty five the Jeep drives beautiful. When I drive on the freeway in excess of roughly sixty five for an extended period of time, say for example an hour, the engine will out of nowhere feel like an engine brake has kicked in. When I push the gas pedal the jeep will decelerate pretty sharply. When I pull over to the side of the road, turn it off and turn it back on and keep going it will do it again a few miles down the road. It also does it if I really lay on the gas and get the RPM's higher up.
If anybody has any ideas about what could be the cause of this, please help me out!

[03Wrangler]

if you could fill out your profile we would know if you had a 5-speed or auto.... and allot more info we need in helping you get this solved...

if you could do that, we could further help you and your future problems quicker...

edit: thanks and welcome to the site

[BJORN98TJ]

alright i'll do that.
the transmission is still the stock five speed. The engine is the stock 4.0L with 100000 miles.

[97tjtom]

sometimes my truck seems to do the same thing, a complete loss of power during acceleration. although for me its usually when i first start up and hit second gear

[BJORN98TJ]

It's more of a nuiscance than a worry for me, cause I really never drive my jeep on the freeway.
I was just curious as to what the cause could be, cause when I called the dealership they were just a little too anxious to get me in there, like it was something important.

[madduc]

When was the fuel filter last changed?

[mdm]

Low fuel pressure? Fuel pump, filter, lines,...?

[Jerky bump]

Would the gas cap affect?

[BJORN98TJ]

Well, I've never checked the fuel filter or replaced it. Gas cap seems fine. I'll check the fuel filter out.

[Saisling]

Well, I was also going to say fuel filter.

If you've never changed it and teh vehicle has 100k miles on it, it's well past time.

It definately sounds like a fuel problem the way you describe it.


I suppose it could be that your fuel pump might be starting to tell you it's getting tired as well. But if it is pump or filter, it will continue to get worse.

I would definately start by at least replacing the filter and see where that gets you. Cheap and easy. With that many miles, when was the last time you did a general tune up?

If it's been awhile, I'd do a tune up along with the fuel filter change then see how it does. Maybe you'll get lucky and the filter will be the only problem.

[Wheelin98TJ]

Originally Posted by Saisling

Well, I was also going to say fuel filter.

If you've never changed it and teh vehicle has 100k miles on it, it's well past time...

...I would definately start by at least replacing the filter and see where that gets you. Cheap and easy...

The TJ fuel filter is in the tank.

Its not a part that is replaced as routine maintenance.

[Jerry Bransford]

Do you ever get a Check Engine light when this happens? The next time it happens, as soon as you can afterwards, extract your engine diagnostic codes by turning the ignition key on-off-on three times within five seconds and wait (could take several seconds) for any stored codes to begin displaying in the odometer. A stored code could provide a good clue as to what is wrong. My first thought is the CPS (crankshaft position sensor) is going bad. The CPS generates the engine's master timing signal and when it stops doing that, sometimes it happens intermittently, the engine will act like you turned the ignition key off.

I doubt it's the fuel filter which was designed (and is truly built) to literally last the lifetime of the Jeep without needing to be replaced.

[FleetPlans.com]

I had a car with a restricted catalytic converter that had the same conditions that you describe. The vehicle ran great at lower speeds but ran poorly at higher speeds.

It might be worth looking into - maybe even tapping the converter with a hammer when the Jeep is on a lift to see if you can hear any rattling that may signal that it has failed.

Good luck and please let us know what you find.

[cmorganf64]

I agree with Jerry...it could be the CPS.....I replaced mine due to the same characteristics that you are having.....but it didnt entirey correct the problem.

I also has a bad Throttle Position Sensor....very similiar problems as the CPS. I replaced it and snugged the wires up on the lug and have had no proplems since.

Start up your jeep and pop the hood. locate the TPS (drivers side, on the back of the intake manifold). See the harness? Grab the wires (gently) and wiggle them. If your engine dies, coughs, surges, etc...then the wires are a bit loose in the harness. Shut off the engine and pug the plug from the TPS. Tighten the wires up in there and re-attach.....start it back up and try it again. Maybe that is all that it will take!

good luck!

chris m

[BJORN98TJ]

I've never gotten a check engine light before when it does it. I did replace the TPS about two years ago, but I will also check it.
The situation you described about the engine losing total power like it's off is exactly what it's like, but it continues to run. How difficult is it to replace the CPS?