I'll start off by saying that I've been searching through existing threads for 2 weeks and have just gotten to a point to where I need some specific help in diagnosing an intermittent sputter/surge/misfire issue on my 1998 Jeep Cherokee Sport 4X4 w/4.0 and automatic trans. It started occasionally sputtering and cutting out after about 15 minutes of driving it. It acted like a coil or distributor related issue. I pulled the coil and the casing was busted and there were visible burns where the wire to the distributor goes. I thought "great! that's it". Changed it and no difference. Popped off the distributor cap and sure enough, it looked fried too. Changed the cap, rotor & pickup...no change. The distributor had some axial play so I went ahead and changed the whole thing. No change. I decided to just throw some money into it because when I bought it three years ago there was no maintenance history and I want it to be reliable although it's rarely driven. I went ahead and changed the TPS, CPS (both MOPAR) and fuel pump assembly(Carter). None of this did anything. I checked the wiring thoroughly and didn't find any bare or visibly damaged wiring. I also checked the MAP sensor and it wasn't getting any voltage out of it. I have 5v going in and it's grounded (multimeter connected to positive terminal and then pinned the #1 and it showed 12.8v) but not getting ANY voltage from the sensor to ECU pin. Changed out MAP and it too isn't showing any voltage.

When it happens it kind of surges like the fuel pump is cutting in and out and it backfires and sputters. I just press down more on the gas pedal and it lines out and acts right for a little while. It idles perfectly all day and will sustain high speeds fine but acts up between 35 to 60mph . I'm stumped.

I've got a couple questions:

1. Could the MAP even cause the kind of drivability issues I'm experiencing?
2. Can an upstream O2 sensor cause this? I saw in the sticky's that a downstream O2 couldn't be the issue)
3. Should my fuel system status show "Open Loop" (see screenshot from my OBDII monitoring session)
4. What's the normal Intake Manifold absolute pressure?
5. Is there anything else that looks funny with the sensor readings?
6. Does it mean anything that the problem is alleviated (even briefly) when I stomp on it?

Thanks in advance!! I really am stumped.

OBDII Monitoring Session

 

I'd think you would be in closed loop, with it warmed up and at idle. Odd that the o2 sensor shows exactly 1.0 volts.

 

I give myself the idiot of the year award! After two weeks of diagnosis and swapping parts I finally pinpointed it to a bad ground cable!!!! It was just loose enough that when I was bouncing down the road it would lose contact! I tightened it and it ran great for about a 20 mile drive. I took a bit of a sharp turn and it started the same thing again. I checked the ground and the cable had loosened up again. The battery hold down/securing bracket was a little loose so I tightened it down, tightened the cable again and drove it for 50 miles without a single sputter or anything. Ran better than it ever has. I feel like an idiot. At least I’ve got a new fuel pump, distributor and sensors. Should be nice and reliable for a long time!

 

Yeah, I always start with the basics like grounds for intermittent problems. I had a 93 ZJ that would die on bumps and always fired up once towed home. It finally stayed dead long enough to discover that all of the ECM ground wires come to a single wire connector by the battery that got smashed.

 

Don't feel too bad. I chased a problem for a year that turned out to be a bad O2 sensor that I thought my son had replaced. Turns out he didn't realize there were two, and he replaced the rear one.

Popped in a new one in the front position and life was good.