2000 bogs in first gear from stop

Hello, I've got a number of sudden issues that I wonder if they are related. The rig: 2000 XJ Sport, AW4, 4.0, 3" lift with 31" BFG ATs. No SYE or other driveline improvements (in other words, stock) 120k on it, with regular oil changes.

About 2-3 months ago I noticed a strange vibration in the gas pedal when I would take off from a stop. At the same time, the engine seems to bog down a little. If I don't mash the gas and take off slowly, the vibration doesn't happen. It struggles on the uphills from stop-~10mph. I've also started spinning the right rear tire from a stop if I take off quickly--even on pavement. This makes me think I've got something wrong in the rear end, but the "bogging" of the engine doesn't add up.

Also, after driving long enough to get temp to ~210, the engine stutters horribly if it is turned off and back on. Only waiting for the engine to cool significantly seems to make that better. Radiator is good and I've had recent flush and fill. I've done a plug-only tune up, but that was a while ago.

Now, today, the check engine light came on. O2s were replaced about 2-3 years ago (40-60k ago)

Oil level is good and regular, trans is clean and full, transfer was serviced less than 2k ago, diff fluid changed ~30k ago and full, doesn't overheat--but rubs right up on 210+.

I don't know if they can be related, but it seems like it all came on bit by bit. The bogging and restart stuttering are a real concern, and the vibration that accompanies the bogging causes a little bit of alarm.

I want to take it in for service anyway, but any good advice going in would be very appreciated. I'm thinking the transmission has something going on, and the other vibe might be u-joints? I'm obviously clueless! Thanks!

...anyone have any advice?

With a check engine light, you really have to read the codes first and start there. Guessing is futile. The OBD2 system in your Jeep is pretty advanced and can "generally" point you in the right direction. I'd suspect the throttle position sensor is a possibility for your engine bogging symptoms. Checking fuel pressure may not be a bad idea either....Good Luck!

birchlakeXJ said:

With a check engine light, you really have to read the codes first and start there. Guessing is futile. The OBD2 system in your Jeep is pretty advanced and can "generally" point you in the right direction. I'd suspect the throttle position sensor is a possibility for your engine bogging symptoms. Checking fuel pressure may not be a bad idea either....Good Luck!

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x2

also search for heat soak, could be the number 3 injector is getting too hot and causing a misfire.

how do the plugs look and what plugs are you using?

89xj said:

x2

also search for heat soak, could be the number 3 injector is getting too hot and causing a misfire.

how do the plugs look and what plugs are you using?

Click to expand...

The plugs look clean as they should be with plenty of life left. Champion truck plugs are in there now.

Interesting thought about the injector. There have been some misfires when dealing with the restart stuttering when I try to give it gas. If I gently apply the pedal it will slowly even out. It looks like the fans (elec and clutch) both come on when they should, so I'm not sure what is up with the cooling system...or if it is a problem.

The more research I do make me think TPS, and I may start there. I do have a good mechanic that I trust, so at least I can call and ask what it would take to get it done anyway.

Oh, and the Check Engine light has reset now. That's interesting. The code reader should still find recent codes, right?

Thanks!

Any other thoughts?

Yes, even if the check engine light is no longer on, there is a code set and it can be retrieved. 3 minute job. I wouldn't replace anything until I know what code(s) are set.