Irritating misfire.

[rugidone]

95 Cherokee Sport, 4.0HO, AW4.

I went wheeling all day in the mountains yesterday, jeep worked great all day, and I mean not a hiccup, no overheating, no misfiring nothing. UNTIL I got out on the main road. Had trouble getting up to speed with the engine hitching and going on, got back and put on my spare dist. cap, plugs and wires which all worked great prior to removal, and pulled the cat(been making noise lately so figured it plugged up) and replaced it with a test pipe trying to rule it out. Still no change. No Powertrain codes coming up. The exhaust manifold is glowing red as well, obviously a good sign of raw fuel.

Anybody have any ideas where I should go next without throwing tons of cash at it trying to troubleshoot?

Its starting to get irritating and its a daily driver.

[rugidone]

Fuel filter is only about two months old as well.

[4x4Dalton]

Check all yer Vacuum hoses. Big ones and lil ones as well. It sounds like it may be one of them has came loose or dry rotted.

[rugidone]

Will definitely add that to my list to check!

Its just so frigging weird that it worked fine on the trail without a miss, the gravel road taking us back out to the pavement (65km/hr) and it worked fine, in fact in one of the corners I was rooting on it and breaking traction, then we stopped at the end jumped onto pavement and hit the gas and it fell on its face.

[rugidone]

I also noticed, starting it cold, it will rev up to nearly 2grand then drop right back down and try to stall, sometimes it catches itself and comes back up to 800 or so, sometimes it stalls(it starts right up though)

[reddragon72]

sounds like a stuck throttle position sensor. You could also have a dead injector pouring gas into a cylinder, but I think TPS sounds more accurate.

[rugidone]

Would the tps normally cause a misfire though?

[4.3LXJ]

I also noticed, starting it cold, it will rev up to nearly 2grand then drop right back down and try to stall, sometimes it catches itself and comes back up to 800 or so, sometimes it stalls(it starts right up though)

You can clean your Idle Air Controller to fix that.

[4.3LXJ]

95 Cherokee Sport, 4.0HO, AW4.

I went wheeling all day in the mountains yesterday, jeep worked great all day, and I mean not a hiccup, no overheating, no misfiring nothing. UNTIL I got out on the main road. Had trouble getting up to speed with the engine hitching and going on, got back and put on my spare dist. cap, plugs and wires which all worked great prior to removal, and pulled the cat(been making noise lately so figured it plugged up) and replaced it with a test pipe trying to rule it out. Still no change. No Powertrain codes coming up. The exhaust manifold is glowing red as well, obviously a good sign of raw fuel.

Anybody have any ideas where I should go next without throwing tons of cash at it trying to troubleshoot?

Its starting to get irritating and its a daily driver.

How many miles? I almost suspect cam timing has changed allowing the valves to open too soon and have burning fuel escape before being burned. That would explain lost of power too.

[rugidone]

Well I fixed it, went and changed my TPS, and checked all my vacuum lines(the ends of one had deteriorated to nothingness) but it still wasn't cured. So I took another look at my distributor, was going to reindex it, but then I noticed it was LOOSE!, the hold down bolt was only finger tight, which explained all the bouncing around it was doing, torqued it back down, took it for a test drive and its A-1 now.

BTW, there is 367,000 KM on my rig, I am going to go through everything and reinspect everything I ripped apart trying to fix it.

[rugidone]

Thanks for the advice though!!!

[4x4Dalton]

Thanks for the advice though!!!


Glad we could help ya bro!!

[rugidone]

It feels good to be able to get on the gas now!

Now to fix my ebrake cable.

[rugidone]

Going to bring this back up as something similar has come up.

(Intermittent problem)
After heading to work, the jeep runs great for the first couple kilometers then picks up a lack of power attitude until it reaches higher RPMS then takes right off, Plugs/wires/cap/rotor button are all recent.

Shut jeep off, restart and normally, problem goes away.

Now Friday, while it was in one of its gutless moods, it actually broke down, and had a hitching misfire til I got to where I was going, shut it off, restarted and ran fine the rest of the drive.

Any thoughts?

[4.3LXJ]

How old is your O2 sensor?

[rugidone]

How old is your O2 sensor?

6 months or so, probably around 5000km on it.

No codes either.

[LizardRunner]

yep that sounds like it could be O2 sensor related. running good till it's warmed up the stumbles till higher rpms.

[rugidone]

Alright, just an update.

This past weekend, I changed the exhaust manifold, downpipe, 02 sensor, center sections and muffler to eliminate the leaks.

Cleaned intake, throttle body and the IAC, I also changed fuel filter and CKP.

Problem is still there, if not worse, it wants to die when rolling up to a stop sign.

Still behaves like before though. Intermittent boosts of power, its really sluggish and getting hard to drive. While cruising and slowly getting up to speed, sometimes it will take off like it should for a few moments then when it upshifts it goes back to the sluggish misfiring pile of metal.

Any insight?

[4.3LXJ]

Do you have a fuel pressure gauge? I think it is time to look at that.

[rugidone]

Hmmm, I changed the coil and the temp sensor tonight. No change.

Decided to head home for the night, once I got here, I unplugged the 02 sensor for chitz n giggles, hmmm no stumbling....took it for a rip around the block a few times, no stumbling no power loss.

Safe to say it is 02 related, Im thinking its the plug/wire for it.

[rugidone]

I looked at fuel awhile ago, all was normal.

[PolarXJ]

All I can say is GOOD LUCK. Everything that I thought that could be giving you issues have been mentioned. Keep us updated.

[uberxj92]

went thru this once or 4 times myself. seems it's something different every time. once it was the tps, then the map sensor, fuel injector leak, vacuum's, but the one that stumped me was on my 93 ( god have mercy on it's soul), turned out it was the ecu/brain. swapped it with one out of a junkyard & ran awesome til that fateful day. she will be missed but she did get us home after we took 12inches of rain in 6 hours.

[rugidone]

Ya, I changed TPS and even tested it, gone over just about anything I could think of, Comp Test and Fuel Pressure Test are still on the list, gunna see about gathering up an ECU though.

[xj4life2]

Check the wireing back to the ecm from the o2 sensor mabey its not getting a signal from the o2 causing it it run in "limp home mode" also check that the ecm is putting out a signal to the o2. You can also check the o2 with a volt meter to be sure its switching. I have got bad ones right out of the box. What brand is it ? Jeeps dont like Denso or bosch.

[rugidone]

Checked the compression tonight, 150 across the board, Varied from a hash below to a hash above.

[ralphy]

I would think if it was an o2 sensor issue it would trip a code, my daughter's chevy tracker "cute lil' critter" had the o2 plug get against the exh man and melted shorting it out and setting a code. I would suspect the distributor, Chrysler and Jeep were buddies for a while and I've seen many problems from their distriutors. just a thought.