SoCo_Fox

1996 Cherokee Sport
4.0HO Auto
169,000

Ok. So I'm hunting down hesitation, rough start, backfire through intake, blah blah blah blah. Cap, rotor, plugs, wire, TPS, IAC... done. Still happens. Has air, has fuel, spark seems the issue.

Now that I think back to doing the cap and rotor, the dist. shaft seemed rather loose. Not in the circular motion the rotor spins, as if the gear was worn, but instead side to side, as if an upper bushing in the dist was worn. If I grabbed the rotor, I could move it side to side a good bit, at least a 1/4 inch. I remember thinking, "That doesn't look quite right." But I went on my dumb way and replaced the cap and rotor.

Things were good for a few days and then it went back to acting up. I know a lot of people on here would usually suggest I try the CPS first, but that dist play can't be normal, can it?

Since I did all the tune and sensors, it runs amazing, when it's not acting up. When I floor it, it feels like the timing is pulled way the hell out, and really restrained, my Mustang felt like that right after I did the dist and hadn't set the timing yet. But when I back off the throttle just a little, it jumps forward as if I released it.

I know I'm going all shotgun trying to hunt the problem. But it needed all that other stuff changed anyway. I suppose I could just take a trip to the parts store and see how a new dist. feels. Might just pick one up and swap it out for the hell of it, looks as easy on the Jeep as on my Mustang.

I have a feeling I'm going to have a forehead slapping moment just like when I figured out it was the dist. on my Mustang.

~SoCo

fantic238

No, it's not normal, and that might be your problem. Is only the rotor moving or also the shaft underneath?

fantic238

That sounds like low fuel press to me. Is the pump making a whining noise?

SoCo_Fox

I noticed the play in the dist. when I had the rotor off to replace it. It's the shaft itself, the rotor fits snugly, but then because of the shaft, it all wiggles.

When it stumbles and backfires, particularly when it's cold, it has that sweet smell of unburned gas from a really rich mixture, so I'm fairly sure it's getting fuel. I would think the backfiring would suggest the fuel is there, but it's getting lit off at the wrong time.

fantic238

If it has all this play it could be that the rotor gets stuck against the pins of the cap.
You should find the signs though.
The fuel pressure has nothing to do with the fuel "feed" at idle.
If the pressure is low it will affect only at high rpms and wide open throttle. The motor just dies because the flow is insufficient.
Check it with a press gauge.

troy fritz

Its your distributor. I have a 96 that did same thing so I replaced. All is well now.

SoCo_Fox

I just looked at how short the Jeep dist. is. The one in my Mustang is really long compared to the Jeep's and if I'm seeing that much play at the end of the shaft, it must be causing havoc with the timing and fuel, considering the cam sensor is up under there as well. Looks fairly easy to replace on the Jeep. Off to the parts store...

~SoCO

SoCo_Fox

Hmm. Distributor didn't help. Can a clogged cat cause problems like this? It was running fine, and then I went to start it a little while ago and it started right up, but was idling really bad. I got out and it sounded like it had a big exhaust leak near the cat, I went and drove it, the problem cleared up, and then when I got home, the sound of the exhaust leak was gone.

mike37

the smell of un burnt fuel O2 or cat

backfiring usually ignition but could be bad vac leak

mike37

open the hood and run it in the dark no street lights
as dark as you can find look for jumping spark

SoCo_Fox

It's all good as far as that's concerned, new plugs, wires, cap and rotor. Fuel pressure is good. Distributor is now new. TPS, IAC good.

That exhaust leak by the cat is something I hadn't noticed until tonight. It was really bad when the engine was running like crap, then it went away when the engine started running better. I gave it a knock tonight and didn't hear anything rattle, and I'll see what my gas mileage is later tonight.

palmrose2

x2

You have the classic symptoms of low fuel pressure. Maybe all you need is a new filter. It's usually mounted along the inside of the "frame rail" mid jeep.

palmrose2

If the mixture is to lean it won't ignite. Therefor you will smell gasoline from totally unburned exhaust. Every time an engine misses that mixture is unburned. Not enough fuel is particularly troublesome when the engine is cold. Cold engines require richer mixtures to run correctly.

SoCo_Fox

Well, it seems that ultimately it was a bad ground. Everything looked good upon inspection, but then the Jeep wouldn't start the other day, and it was acting like it had a bad battery. Thing is, I replaced the battery a few days before. I cut some of the insulation off the negative cable and it was corroded pretty badly within the cable itself. Took care of that, been running like a champ since. Go figure.

And it wouldn't be a Jeep if I fixed one thing and then there was something else... now the rear main seal is leaking. Joy.

~SoCo

PA_jeeper96

notice how he stated that the distributor shaft has play defientely not fuel pump related