basic

I had made a similar thread, but this one is more detailed and doesn't have the transmission stuff (because i don't think that is the problem - read on)

Jeep info:
97 XJ 4.0 w/ AW4 - Police package and upcountry suspension. A former Illinois Dept of Conservation Vehicle. Has 218k miles on the clock.

Here's the symptoms:

Erratic idle (sometimes it will die, most of the time just jumps between 250-750 rpm, sometimes will stumble, catch itself, and idle up to like 1200-1500 rpm then go back to the bad idle)
When warmed up (within 5 mins of driving) it looses power. Sometimes while its in third, all the time in forth. Generally under load like going up a hill or while accelerating. If you floor it and make it shift into 2nd, sometimes seems to be ok, but once it shifts back to the other gear, it will stumble and stall out - sometimes dies, sometimes doesn't. It feels almost like it's run out of gas. Also may be a small backfire, i can't tell.

If it's in first there don't seem to be any problems. Does have problems in reverse and dying (attribute that to erratic idle). Did have it die once after backing up and shifting to first. Otherwise plenty of power and doesn't feel like there's any lack of it. Only ever had it do in once in 2nd, going up a steep hill.

Throwing codes p1397 (intermittent CKP or CMP) - Both have been replaced.

Was throwing a code for the range sensor - removed and cleaned that, now it works and the back up lights work again. No Code anymore

Parts replaced (this was my step fathers and he likes to throw parts at things in an attempt to fix) -

Cap, rotor, wires, plugs
CMP (with Distro)
CKP
TPS
MAP
Fuel Pump
PCM
Seafoam in the intake as per manufacturers instructions (brake booster vacuum source, 6 oz of seafoam sucked in slowly, let sit 5-10 mins, restart and wait till smoke clears)
Removed exhaust from ahead of cat back to see if it was clogged cat, no change. Just much louder.

Grounds cleaned - both the ones by oil dip stick, and one from rear of head back to the firewall. Also an additional ground has been run from battery to vehicle frame.

I have tried running with both o2 sensors unplugged, still problems (and a code for o2 sensors)

Any ideas what else this could be? I have a 92 parts jeep I can "borrow" parts from if they are compatible (a lot aren't).

Any help anyone can give would be appreciated. After working on this thing for the last 4 days, I'm tired of working on it. I'm thinkin it may be o2 sensors or a temp sensor (either coolant or air intake). The internal temp gauge works good though, and the electric fan is working well. I'm also wondering about the ignition coil.


I'm about to the point that if someone can tell me what the heck it is that I would pay them for the info. That's how sick and frustrated I am with this.

If I think of any more symptoms or anything I'll post them.

freegdr

where do you see p1397 code listing for 97 xj cherokee?????

freegdr

dont no maybe this will helphttp://www.jeep4x4center.com/knowled...ex.htm#service

DaddyCat

Have you reset the ECU after replacing those (many) parts?
http://www.quadratec.com/jeep_knowle...article-89.htm

razor02097

He said he replaced the PCM.


Drive it around at night to warm it up. pull over and look at the cat under the car. If it is glowing then it is clogged.

How does it run the first minute or so on startup when cold? Better? It could be a lazy (slow responding) or defective O2 sensor.

Are you getting a check engine light?

If all else fails there is no shame in asking a pro to help... The computer on your Jeep is pretty smart. With the right tool it can tell you what is wrong. If you have a trusted shop that can properly diagnose the problem you can either fix it yourself or have them do it.

tiwvr1

Did u try pulling out the Idle air control motor, cleaning the pintle on it good, and clean the bore that it sits in.

basic

sorry, it wasn't p1397, it was p1391. Couldn't read my own handwriting.

Going to test the coolant temp sensor this morning.

Don't think it's the cat as I have run it without cat on the exhaust (running open dump from ahead of the cat - really loud and still had the problem).

Also heading to the parts store for TB cleaner. Going to pull the AIC and clean it and the TB hoping that will help the idle.

And yes, still getting CEL. I reset it last night. After testing the Coolant temp sensor i'll take it for a drive and I'm sure they will pop up.

As for running better for the first couple mins when cold - yes. Doesn't have the loss of power issue. Still has crappy idle though. I was curious if it were the o2 if it would still have the issue with no o2 sensor hooked up?

sflxj

Replace the ignition coil first. If that does not help try replacing all of the O2 sensors.

The ignition coil is probably cracked. it has happened to EVERY 4.0L Jeep I have ever owned.

jeepgirl99

I haven't heard anyone use the expression "wits end" in along time, but have to share this with you now that you have said it! This is our real road sign.

basic

ell, coolant temp sensor tested ok (11.5k ohm @ 65F, ~700 ohm after engine warmed up).

Coil was cracked, replaced with coil from parts jeep, no change. There was a small crack on the parts jeep coil, so will try replacement coil.

Also, doesn't seem to be showing any codes via the CEL method anymore. Just getting code 12 and 55.

Will also try o2 sensors I guess since there's no way to tell if they are bad.

As for the wits end sign..that's about how I feel. Bad, I'm glad I gave you a chance to use your picture!

garb.man

Really sounds like the IAC (Idle Air Control), check all vacuum hoses and intake/exhaust gasket, one of the guys in JP mag had an mj with very similar issues, erratic idle/rpm, it came down to a combination of cracked Exh/intake manifold and a blown out intake/Exh gasket.

4jeepers

After replacing all those parts it is a good idea to take a long drive in the vehicle. This will give the ECM time to learn all the new sensors. I do this every time I disconnect the battery as well.

TheDale

Mine was doing something similar, and it ended up being a broken wire that goes to the injectors, I think it was the injector power wire. If you can get it to run and idle, try wiggling the engine wire harness and see if anything changes.

basic

Well, new front and rear o2 sensors are on order. Should be here early next week.
I did try wiggling wiring harnesses with the engine running. No change and problem is still there.

The stumbling and loss of power keep me from being able to take a long drive. It will not make it 2 miles before having the issue, and once it starts stumbling it is undrivable.

Funny you should mention the exhaust gasket - while driving to see if the ignition coil helped the problem- it blew out the exhaust gasket near #1 cylinder. I didnt think there was a leak, but now that i think about it there was some smoke coming from engine compartment while seafoaming. That may have also been contributing to the eratic idle. Wondering if a malfunctioning o2 is causing to run rich, it backfired through the exhaust, and the increased exhaust pressure blew the gasket. Will never know, but its a possiblity.

I did not get a chance to check/clean IAC - something came up and I had to head back home three hours away.

I will post updates as soon as I have any.

dukie564

IAC will not cause the problems while driving at speed

That exhaust gasket leak is your culprit. It's throwing the o2 sensors WAY off resulting in your issues at idle and while driving. Replace the gasket before throwing any more money at other items.