jowint

The ticking purge valve just means it is working to pull a vacuum on the fuel evap purge system to check for leaks in a self test mode.

If a large leak is detected anywhere in the system it will set the po455 code.

It could be a leak anywhere in the fuel vapor containment system......OR, this may sound weird, but you may have accidently trashed your charcoal canister by overfilling the fuel tank at one point by topping off too much.

Most fuel filler necks have a vacuum line that goes into the side of the fuel filler neck that is part of the fuel evap purge system under vacuum test.
Check for any vacuum lines at the filler neck, and try to remember if you ever overfilled your tank prior to that check engine light coming on.

If you over saturate the filler neck there is a chance liquid fuel can go into the vacuum line and trash that charcoal canister which will result in a permanent check engine light/po455 code that will only go away once the charcoal canister is replaced.

I am not positive your Jeep has this line in the filler neck but i can tell you that I have seen this before on numerous other model vehicles.

Check all rubber lines and seals to the purge valve and the charcoal canister, intake area or anywhere else those lines can go.

I have also seen charcoal canister shut off valves leak due to a weak rubber internal diaphragm.

The dealership can turn you charcoal canister shut off valve on/off using diagnostic tools in conjunction with a vacuum gauge to see if the evap purge system is holding a specific amount of vacuum within a certain time frame to determine if you have a leak.
Sometime the shut off valve seal will trick you and not act up, but in most cases if it's bad, it will not hold vacuum.

If it holds vacuum well, I would suspect a contaminated charcoal canister with raw fuel.

sv41878

Just asked the same question recently, turned out to be the 02 sensor and it never threw a code. It finally let me pull the codes manually (still no check engine light) and it said both rich and lean condition detected (separate codes). I thought it was a fuel issue when it first started to do it myself.

moparchero

I wanted to re-up this thread, because I'm having a very similar problem and I'm quite stumped. Engine stutters intermittently, usually when I'm on the highway and it's under heavy load (75 MPH+). I have no tachometer in my jeep, which is a 98, 2.5l, and stickshift.

As far as the trouble shooting, I've put in new plugs, wires, cap, rotor, battery, and clutch in the jeep within the last year, since I bought it. I've tested the fuel pressure, which reads a steady 45 while idling and also while neutral and the foot down on the gas.

I've never had a problem starting it, and it doesn't idle rough, but this engine stuttering comes and goes and it seems like it's getting worse lately. I figured it either has to be a fuel or spark issue, but both systems seem to test out perfectly fine.

The trashed charcoal canister and the evap canister sound like useful troubleshooting ideas. I'll check them out tomorrow morning, and see if I can get anywhere with that.

DFlintstone

Have you changed/back-flushed the fuel filter? It might maintain pressure under low flow, but crap when asked for high flow. Regular maintenance anyway, maybe take that question out of the equation.

moparchero

Upon investigating the other day, I decided to take out and check my ignition coil. It was pretty corroded with rust. I tried to look up some tests for it, but I couldnt find any information on it in my Haynes manual or online anywhere. I decided i should replace it regardless, and I took it on a spirited drive. The jeep only stuttered once, and it wasn't even that bad. I'll keep watch over it the next few days and update the news on here

Jason400

Have you checked the O2 sensor? Unplug the upstream sensor and drive it.

s346k

wow the op had a misfire and it took almost a month to investigate the ignition system? sigh

moparchero

Ignition coils been changed out, and I've been driving it for a few days. The stutter is still happening. Now I'm trying to think of what else it could be.

Couldn't be the clutch, its only 8 months old.
The 02 sensors upstream and downstream were replaced a few months ago to clear a code for emissions.
Could be the fuel filter, but on a 98 its not a serviceable part, since its built in the pump inside the tank.

I don't think its a fuel issue, as those are more gradual declines in power over periods of time, where this is just a really sharp jab, like i just gave the brakes a quick pump, and then its done.

It's usually at higher loads, but I think that's just because the engine RPM is higher, giving it more chances to stutter. Any other ideas?

s346k

plugs/wires been revisited lately?

DFlintstone

Whoops, edited.

For one, higher compression under load makes the voltage needed for the spark to jump the gap go up.

moparchero

No point starting a new thread when there's a similar one already. But nevertheless, the problem still isn't solved. it's still doing it, so no celebrations yet.

as for the plugs and wires, they're only about 6 months old. same goes with cap and rotor.

DFlintstone

I'm not sure what I'd expect from a 2.5 under heavy load over 75 MPH. I'm not sure my old (carbed 84), 2.5 even goes 75. Even though they are fairly new I might pull, inspect, and gap the plugs.

Seth Morrison

My girlfriends jeep is doing the same thing stutters on backboard at 40-45 and on the highway over 60 we replaced cap and rotor plugs cool wire both fuel filters and problem persists hers is an 86 and you can hear a vacuum leak but that has been there since she bought it a few months ago I also pulled the cat off to see if that's the problem and it didn't seem to help I'm leaning towards maybe a carb issue or something but not sure anyone have any clue on these older jeep cherokees