rmatt

Hello All. First post a problem. Have a 1998 Cherokee 4.0 eng manual trans. When first started it runs fine in 1st and 2nd gear, maybe 100 yds. At the first intersection runs ok until 3rd gear, then starts to stumble and backfire through the exhaust. Push the clutch in and wind it up and sometimes clears it for a bit or if you mat the gas in gear it hesitates for a little and then goes. It continues for a half mile or so the it is fine for as long as it is driven. Shut it off for 10 -15 min and go thru the same thing all over.No engine light and no codes.
I have replaced the Cat as it rattled, replaced the tps.
I used the search feature and read what seemed relevant.
Any ideas would be greatly appreciated.
Bob

Bustedback

Check the fuel pressure, sounds like it's starving for fuel.

tjwalker

Or too much fuel. Backfiring out of the exhaust can be a rich mixture.

But I agree that testing of fuel pressure is #1. Should be 49 psi, plus or minus 5 psi.

If that checks out, test the MAP sensor as that is also involved in determining fuel/air ratio. It can be tested and be sure that the vacuum line leading to that sensor is pulling good vacuum.

Slick761

Sounds like.map to me.

rmatt

Wouldn't I get a check eng light if the MAP sensor was faulty?

tjwalker

The OBD technology isn't perfect. There are actually quite a few "escapes" (issues for which no check engine light or code is set)

OllllO Isaac

I am having problems with my jeep when I try to start it up. It cranks but don't start. It backfired real loud this morning when I tried to start it. I think its the crankshaft position sensor but I'm not sure. Can somebody help me please??

Slick761

Start a new thread man. It will help.

tjwalker

Yes, each new problem / new person gets a new thread. Otherwise, the original thread gets too confusing and nobody wins. Called "hijacking".....

99 Purple XJ

If back firing yours sounds like an issue related to weak fuel pressure same thing i had