94xjse99xjsport

Hey guys my 99 has had a problem for awhile now. Occasionally when I take off down the road, the jeep will start to miss. If I stay at the same throttle it will just keep missing, but if I add some throttle, I get a backfire through the throttle body and the jeep runs great? Its got me so confused. Any Ideas?

ZINGGG

What maintenance have you done? If any?

94xjse99xjsport

Plugs, wires, cap, rotor. Fuel pump, cps cleaned throttle body. Has regular oil changes. And no check engine light

ToasterOnWheels

Mine does this once a month or so. If I let off the gas the press down again its fine. I attribute it to a bad attitude.

94xjse99xjsport

I thought that at first but mine has been getting worse. I just worry that one time its just gonna die.

ZINGGG

Ever replaced the upstream o2? How's your exhaust manifold look? Any cracks in it?

VTJeep

Haha.. x2 on the o2 sensor. Hesitation is probably sign of fuel delivery issue. Even if the CEL isn't on, there's a possibility a code is stored in there. And either way, a good diagnostics machine can tell you a lot. Like if your o2's are reading improper voltage..

ToasterOnWheels

Mine did have an issue like this a year ago it was really bad worse than you described. It smelled like rotten eggs, and had like 8 mpg. It ended up being the o2 sensor but no CEL.

scruffythewild

I have the same problem, Check your MAP sensor and I forgot the other ones name...DARN!!! but good luck-Rob