What’s up fellas. As the title states, this is the weirdest thing I’ve came across. The damn Xj took a crap on me on my way to work last week and had to tow it back home. I was having a great morning sipping my coffee going about 65 on the freeway when the jeep started bouncing from 2700 rpm’s down to 1000 a couples times before dying. I pulled off the the side of the rode and it started right back up. I let it idle for a minute and then put it back into drive and it did the same thing when I started moving. Put it back in park, fired right back up. Slapped it into drive and didn’t push on the gas. Everything seems fine… started moving and gave it gas and it died again. Now this is where Im stumped. I put it in neutral and got the Rpms up to like 4k and everything is fine. I put it in reverse and went as fast as I could without crashing lmao and it didn’t die or bog down. Now this is the weirdest part. I put it back into drive and kept my foot on the brake and got it up to 2k rpm and everything is fine, let my foot off the brake and started moving and it died again. I’m at loss here boys

 

Have you tried resetting your Tranny cable.? Three cables going over the valve cover. The one nearest the front of the engine is the cable you want to push the button down and push the cable at the black thingy around it to the drivers side until it stops. Then go inside and push the gas peddle with the key off engine not running to the floor. and let up and then start it up and see what it does. It clicks as you push it to the floor with engine off.

If that doesn't do it try replacing you TPS ( throttle position sensor. On the back of the throttle body. Two screws and a plug. About 31.00 on Amazon. There are cheaper ones but trust me they won't do it.

 

Okay I’ll give that a shot when I get home from work thanks !

 

just a thought

I’ve seen bad motor mounts pull on wiring harnesses cause weird problems, that may explain the forward/ reverse thing?
Check mounts and wire harness behind engine.

 

The shift selector is primarily an electrical switch, so if it runs in one state and not another I immediately suspect an electrical ground for the tcm and shift selector under the passenger dash. With computer related issues, I always start by cleaning and upgrading all the grounds.

 

thanks for the reply, hopefully I can get some time to start digging into it a little deeper. I’ve went through and cleaned my throttle body and replaced a couple of vacuum lines that had some weathering but the problem still persists.

 

Another find, while in drive, I can keep my foot on the brakes and he the jeep up to 3k rpm’s to the point it will start roasting the tires lol. As I le off the brake and start moving it will start sputtering then eventually die

 

Have you started with the basics? Verify fuel pressure and spark?

 

I have a leaky brake booster so when I hit the brakes my idle goes up about 200 rpm. Combined with a sticky/slow idle air control you would have a case for brake pedal causing throttle.
You cleaned the throttle body, did you check out the IAC?