my 1995 ZJ with 4.0 has a bad stumble to it. in park it revs fine, but under a load, if you tromp it, all it does is stumble and fall on its face. tried some fresh gas (who knows how old the other stuff was) with some fuel injector cleaner and it did not help. any other ideas on what i could do? probably gonna seafoam it this weekend and see what that does for it.
this was discussed a while back,and the thread got closed. seafoam will not hurt it. the o2 in a jeep i smade of the same stuff as an o2 on a GM,ford, or any other make. no reason it would mess up on a jeep and not on anything else.
but back on topic, no idea on when the cap/rotor/wires/plugs/filter was all changed. i just bought it 2 months ago and have not evern messed with it till this past week, when i pulled out onto the road and tromped it to do a nice 4 wheel drift into the other driveway. it spun a little bit then fell flat on its face.
i will pull the plugs and see what they look like.
Did you pull the plugs yet? My wifes 95 zj 4.0 auto, is doing the same thing. Been trouble shooting it for a couple weeks. I think I narrowed it down to the fuel pump. I put a fuel press. gauge on it, routed under the hood by the windshield so I could road test and check gauge when it stumbles. Couldnt get it to stumble(figures) yesterday, it had 1/4 tank. Wife drove it today, ran good. Went to pick up kid from school and it chugs and stalls with about 2 gals in tank now. I put $20 inthe tank (now its up to 1/4 tank again), put the press. gauge back on. yesterday the gauge read 40 psi consistently, today it would drop to below 20psi when I punched it and was chugging at 20psi then go back to 40psi when I let up alittle. Think I'll pull the pump tomorrow and see if its clogging up , seems to get bad with low fuel level.
would check the plugs and wires first... I've had the same problems in other vehicles and it was always the wires, they may look good but if they're old they're not getting the spark to the plug, especially when the rpm's go up
2000 Grand Cherokee Laredo 4.0 I6
I have the same problem. The idle is fine after we put the new fuel pump in. It has a slight hesitation & surges around the 1800-2500 rpm range. IAC, MAP, TPS all are brand new. Was reading about the connector to the TPS, so I get my husband to check that.
Could it be the injectors? At 150k miles... they are pretty old.
I think the CAT is bad/old & I'll have that changed too later with the 02 sensors.