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whats wrong with my heep?

SurfXJSnow

NAXJA Forum User
So, were on our way back and something is seriously off with my jeep. This morning when we took off everything seemed fine. Then, coming off an exit in West VA earlier i noticed as i was slowing down, my engine seemed to be "putting"... Meaning my muffler sounded more "put,put,put" then usual. So i hit the gas to accelerate and noticed my jeep accelerate kinda jerky, like it wanted to stall. I popped the hood at the rest stop and noticed the engine seems like its shaking around a bit more than usual. Jeep is idiling a little below the "1" on the guage, which i guess is 1000 rpm? The thing thats weird is that when i hit the gas, it sounds just fine and stops shaking, and when im doing anywhere between 10 to 80 mph i dont notice a change... its only when going around 5 mph during acceleration and when idiling.

Spark plug? Spark plug wire? bad gas? We made it to indiana without it stalling out, but we're going through Kansas tomorrow so i want to make sure its nothing serious before i break down in "Nowheresville". Thanks in advance.
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i live just off I70 in Missouri. You are welcome to swing by and i will hook the scanner to it etc. i have a few spares laying around, as well as trade accounts at the local parts store.
shoot me a pm if interested.

martin
 
how long has it been since you did a tune up?
 
If you are not sure about your spark plugs, take them out and take a look at them. The gap should be .035" and they should be very light tan. If one plug is different than the others, somthing is wrong on that cylinder, hopefully the spark plug or wire. If the plugs look dark and oily, ot the gap is over .050", get new plugs.
 
ok guys,
the OP just left here after a couple of hours of wrenching.
scanner was giving a code P0301, cylinder #1 missfire.
looked at #1 plug, and decided to get new cap, rotor, wires and the correct champion plugs. all plugs gapped @.035.
after a little running, got the same code!
i swapped my injectors to ford motorsport injectors a week ago and kept my old injectors, so installed one in #1 cylinder.
the old one looked like crap after 150k miles.
after a run up the road, it threw the same P0301 code again!
did a little more rooting around, wiggling plug wires and so on. all plugs are now getting a good spark, so i doubt any ignition issues.
also tested the injector plugs with noide lights, getting a good pulse at the iinjectors.
unplug an injector while running and there is a slight change in engine pitch.
when he left here, all was well so i am hoping we did cure it, but i am dubious as it started acting up after the first time round.
when it acts up, the idle goes from 750 to @1000 rpm's. vacuum was between 16 and 27 in hg. so good vacuum i think!
time permitting i would haev pulled the plugs and done a comp test, but they had a long drive and low comp isnt an "easy fix" so i didnt bother with that.
he did say that it felt a LOT faster on acceleration now, no doubt due to new plugs, leads and so on.
any other suggestions for him, assuming the issue comes back as it did before?
again, the code was P0301.
it is bugging me, as i feel bad when someone drives out of my driveway not fixed!

cheers
martin
 
Martin, we made it to Topeka with no problems. Just checked into the lovely Motel 6 here. I swear, my jeep has never accelerated like it does now. It takes off like its brand new, but still idles a little odd at low speeds. As far as today goes, Karen and I want to thank you and your family for all your help. We are two broke kids, trying to save for our baby and hopefully our wedding once the baby is born. We have never met anyone so welcoming and generous. Really makes me proud to be a Jeep owner.

Ill keep you updated on the status. (if it gets worse, or gets better). After we left, the check engine light came on again, but im just going to act like its not even there until we get back to colorado.

Anyways, thanks again.. and drive safe on your trip to north dakota!

:peace:
 
What year is it? I have had issues with my 96 killing coils, they just crack and then shut down.

Also, I wonder if elevation could have something to do with it, he is from much thinner air than what he is driving through right now. Maybe the ECM is just having trouble compensating.
 
jonathan,
a pleasure having you and your better half around mate, you are welcome anytime!
sorry to hear the cel showed itself again. if it is running good going down the road, i would roll with it and see what shows up when you get back home.
i doubt it is the coil (its a 1998), as it is always showing number 1 cylinder is misfiring. maybe someone can chime in if a bad coil will show itself as number 1 misfire????
the elevation should also be a no go, as the ecm will learn a whole lot quicker than that! i spoke to a friend of mine, and he is thinking the ecm itself, but i wouldnt go down that road until all over avenues have been explored.
try to get the codes read and see if it showing P0301 again. if so, i think my next step would be a compression test across all cylinders. all that involves is removing the plugs and the power wire to the coil, and cranking with the gauge hooked up to a cylinder until all have been tested. it should show a pretty much even number across all 6. i do have the compression tester, but it was getting late after doing the ignition and injector!
keep me posted, and have a safe trip home!

martin
 
made it back to CO Springs. a few of my buddies off the colorado chapter are thinking maybe its my head gasket? jeep got home fine and continued to do well at 70mph. Still idleing a little rough and kinda puttering when stepping on the gas. ill keep you posted. as for now, unpacking and dinner time. Thanks again martin!
 
no problem jonathan!:thumbup:
i would have liked to do the compression test on it, but time was short.... it was 3am before i got parked up last night as it was!
i dont think head gasket myself, as there was no pressurizing of the coolant etc. when the 4.0 head gasket goes, it will normally blow coolant out, dont ask me how i know that:bawl: that was on a 91, but basically the same 4.0 h.o. motor.
it was also reading pretty good vacuum to have a head gasket leak IMO. but i have been wrong before, too many times to count!
keep me posted, this has me kinda stumped too mate.
say hello to karen for us.

martin & cheryl.
 
no problem jonathan!:thumbup:
i would have liked to do the compression test on it, but time was short.... it was 3am before i got parked up last night as it was!
i dont think head gasket myself, as there was no pressurizing of the coolant etc. when the 4.0 head gasket goes, it will normally blow coolant out, dont ask me how i know that:bawl: that was on a 91, but basically the same 4.0 h.o. motor.
it was also reading pretty good vacuum to have a head gasket leak IMO. but i have been wrong before, too many times to count!
keep me posted, this has me kinda stumped too mate.
say hello to karen for us.

martin & cheryl.

No worries on not doing a compression test! you guys were gracious enough to let us come by and for all the work you did. Compression test will be the next thing i do. Hopefully in the next few days or so. Do i have to take it to a shop to do that? what is the special tool i need for it? I would like to try to do it myself and save some money before i get robbed at an auto shop. :tears: Regardless, its running... and getting me from point A to point B right now. I'm kinda hoping for what you said, for it to get worse so maybe its easier to pinpoint the exact problem before i go replacing the entire engine. Oh, and my A/C was blowing nice, COLD air today! It got warm in mid kansas today and karen was thrilled to have the A/C! I guess i was reading the guage wrong when i was trying to fill it last and reading the guage when it was compressing the air, not when it was circulating. I thought my system was way overfilled.

anyways, THANK YOU! :thumbup: and ill keep you posted once i get the compression test done or if it gets worse.
 
hey johnathan,
here is the one i have i think, it is cheap enough to justify buying one, they are VERY handy! advance auto parts should sell the same model as well,
http://www.sears.com/shc/s/p_10153_12605_00902171000P?keyword=compression+tester
glad to see at least i fixed something (your a/c)! makes me feel a little better anyways.
i spoke to another friend of mine today regards your issue. he owned his own mechanic shop for over 10yrs, so i trust his opinion.
he said he would have done everything we did, from the ignition to the injector.
also mentioned a stuck pcv valve would cause the slight fluctuation in the vaccum reading. may be worth getting new pcv valves mate. they should be pretty cheap, and 3 minute job to install! they are on top of the valve cover. just unplug one and stick the new one into the rubber grommet.
back to the issue though of missfire on number 1.
he also suggested a compression test.
i would remove ALL plugs and test each and every cylinder. write down the cylinder number followed by the compression reading.
if #1 is low, try pouring some motor oil (@a cap full) into that cylinder and retest #1. if the reading jumps up, it is pointing to a stuck piston ring etc. if it does not just up, it is pointing to a sticking/blocked exhaust valve.
if all that shows normal, and all cylinders are withing 10% of each other, try anonther ecm from a friend 4.0 xj. so long as it is from the same generation (97-99IIRC) it should work for testing for the missfire.
as you can see, there are plenty of avenues to go down before we start spending any money mate!;)
all these test and replacing the pcv valves should take 1/2 a day including a run to the parts store for the tester and pcv valves, so get busy!!!!!:smoker:

do that and let me know, feel free to call me if you need any help mate.

martin
 
If you do the compression test and all is well, you may want to check your CAT, it could be on the verge of clogging. If you smell rotten eggs or sulfur smell check you cat flow. If it clogs, it will not burn the proper fuel and your O2 sensor will not function properly. Just tossing out my .02

mac
 
If you do the compression test and all is well, you may want to check your CAT, it could be on the verge of clogging. If you smell rotten eggs or sulfur smell check you cat flow. If it clogs, it will not burn the proper fuel and your O2 sensor will not function properly. Just tossing out my .02

mac

i also suggested the 02 sensor to chris, and he confrimed my thoughts that it would throw random miss fires on the code reader if it was anything to do with the 02 sensor. there is no way it would throw cylinder #1 every time. it is a free test though to bang on the cat and see if anything is loose inside.
in my experience, a clogged/worn cat will show itself at higher rpm's, as it has to try to clean a higher volume of exhaust gas than at an idle.
i did checked the 02 sensor with the scanners live data setting, and it appeared normal to me....so i dont know.

martin
 
hey johnathan,
here is the one i have i think, it is cheap enough to justify buying one, they are VERY handy! advance auto parts should sell the same model as well,
http://www.sears.com/shc/s/p_10153_12605_00902171000P?keyword=compression+tester
glad to see at least i fixed something (your a/c)! makes me feel a little better anyways.
i spoke to another friend of mine today regards your issue. he owned his own mechanic shop for over 10yrs, so i trust his opinion.
he said he would have done everything we did, from the ignition to the injector.
also mentioned a stuck pcv valve would cause the slight fluctuation in the vaccum reading. may be worth getting new pcv valves mate. they should be pretty cheap, and 3 minute job to install! they are on top of the valve cover. just unplug one and stick the new one into the rubber grommet.
back to the issue though of missfire on number 1.
he also suggested a compression test.
i would remove ALL plugs and test each and every cylinder. write down the cylinder number followed by the compression reading.
if #1 is low, try pouring some motor oil (@a cap full) into that cylinder and retest #1. if the reading jumps up, it is pointing to a stuck piston ring etc. if it does not just up, it is pointing to a sticking/blocked exhaust valve.
if all that shows normal, and all cylinders are withing 10% of each other, try anonther ecm from a friend 4.0 xj. so long as it is from the same generation (97-99IIRC) it should work for testing for the missfire.
as you can see, there are plenty of avenues to go down before we start spending any money mate!;)
all these test and replacing the pcv valves should take 1/2 a day including a run to the parts store for the tester and pcv valves, so get busy!!!!!:smoker:

do that and let me know, feel free to call me if you need any help mate.

martin

let the jeep sit today without cranking it. probably going up to a fellow chapter members place tomorrow to run a compression test. What is an ECM and a CAT? im glad that the idea of a new head gasket isnt in order! i got scared there for a bit. ill keep you posted after we knock around under the hood again tomorrow. thanks again for all your research and commitment to my sick jeep! you have truly gone above and beyond! THANK YOU!!!!!!!!!!!!! :thumbup:
 
no problem mate!
cat = catalytic converter
ecm = brain box. it is mounted to the drivers side inner fender on your xj. it is the thing i was checking the 3 plugs were in nice n tight on.
keep me posted.

martin
 
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