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XJ's 4.0L Hit an all time low.

Osprey413

Osprey413

NAXJA Forum User
Location
Dallas, TX
Well, today my Jeep ('97 4.0L) has hit an all time low. Let me begin this story a few months ago. In July I changed my spark plugs and wires just as basic maintenence. Install went fine, made sure I put all the wires on the correct plug (by changing one plug and wire at a time). Started engine, idled rough for a few seconds then evened out. Fine. Put my tools away, came back to Jeep and tried to start it. Nothing. Turned over, but didn't start. I took the plugs out and replaced them. Started up with the new plugs. This time I decided to drive over to the mechanic incase it wouldn't start again atleast I wouldn't have to tow it. Sure enough, got it to the mechanic and turned it off. Tried to start it and nothing. The starter didn't even turn the engine over. So the mechanic comes out to look and wigles the battery wires. Engine starts now, but idles and drives like crap. It seems to be missing randomly. Mechanic's theory is that I have water in my gas. OK, I try this theory out. I go through about 20 tanks of gas and I still have the problem. Then, all of the sudden, I get a check engine light. When I got this check engine light the engine had stalled because the RPM's dropped so low that the engine died. Fight with the Jeep the whole way to the mechanic, I had to constantly give it gas to keep the RPM's up. Mechanic looks at it and changes the CPS. The Jeep runs now, but I still have the same rough idle/missing while under gas problem as before, but in addition to those problems the Jeep doesn't like to start in Park unless it is warm. Recently(past few weeks) I have been getting a check engine light weekly. I take it to AutoZone and have them check it out, same problem. The code is for the CPS or CKS. I decided not to change the CPS because the check engine light magically went away after 2-3 starts. Still idles/misses like crazy and apparently at random intervals. I can drive the Jeep one time and have it not miss at all and then the next day barely be able to get out of the driveway. Now, to add to all these problems I have a really bad oil leak. This leak just showed up out of no where. And as far as I can tell the oil only leaks when the engine runs over 3500RPM for an extended period of time (ex. hard acceleration or passing). The leak is so bad that it is dripping down onto my exhaust and smoking like crazy. I even stopped by the side of the road and in the 2 min. that I was there a sizable amount of oil formed a puddle under my engine. But, if I keep the Jeep under 3000 RPM for most of the drive the oil doesnt seem to leak at all. I got home from a 30 mile drive (engine missed alot) and parked the Jeep. Left it running and there was no oil (as far as I could tell) leaking at all. The oil pan had oil on it from the previous leak, but there weren't any drops forming at all. Apparently I have a leaky seal that only leaks at high RPM's. I havent located it yet because this just happened a few hours ago. I am at a complete loss as to what is making my Jeep run so terribly and now with this oil leak I am really distressed. I have no idea what is going on with my Jeep, but it's bad real bad. Any suggestions, ideas, donations, sympathy would be greatly appriceated. Right now I'm in college so I don't have the money to fix these exspensive problems (CPS is $123, and the oil leak will cost an arm and a leg to fix im sure). I love my Jeep and don't want to give it up, but if I can't figure out or pay to fix these problems I may have to sell it and go with a Jap. sedan (the horror). This is how bad of a situation I am in. Please!! Help!!
 
The rear main seal leak will not be as expensive to repair as you might think. It only takes a couple of hours in experienced hands. You can do it by removing the oil pan. You don't need to drop the tranny.
Your other problem is almost certainly electrical. When the engine misfires, remove one plug wire at a time (wear thick rubber gloves) and see how the engine behaves. It should run worse. If you pull one wire and the behaviour doesn't change, you've isolated the bad cylinder.
Replace the simple things like plugs, plug wires, cap, & rotor if any haven't been replaced in the last 12 months. If you're still not getting a good spark after all that, replace the coil. That's another cheap and easy fix.
 
sounds just like when i had my bad Throttle Postion Seneor go bad, ran for crap and wouldnt start half the time (it would turn over however...)

check your battery and make sure the negitive is grounded properly. Also (i know this is dumb and you probably already did it) but disconect the negitive battery terminal for like 20 minutes, then re attach. this clears past fuel/air mix and makes the computer re-learn the mix...
damn computer cars =>
:repair: => :badpc:
 
It ran fine before tune up and bad aftewards ?
What brand wires, what brand cap, what brand rotor, what brand plugs ?? Things don't normally do that just by changing plugs. Did you put dielectric greast on the connections ? Did you lean on anything while you were doing the work ? Did a wrench slip and whack something ? Is the cap seated correclty ?
I tend to use only Jeep OEM caps, rotors, wires and plugs.
 
Did you replace the cap and rotor button? If so, did you ever try turning the Distributor while the engine is running. If not, I HIGHLY suggest trying this first before you start spending $$$ on parts that don't need replaced. Everything that you have told us here about it running ruff and idleing crappy sounds like an adjustment is needed to the distributor. I hope this helps ya out, just let us know if you did or did not replace the cap and rotor.

BTW, I've got the same problem with oil coming out quick if I'm going 65+mph for any amout of time. I've got the smoke a couple of times and the underneath of my jeep gets a nice oil bath lol.
 
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If your oil leak is coming out only when has been run at high rpms, I would also suspect the oil pump. Your rear main seal leaks all the time, and more when the engine is at higher rpms. Is the leak forward in the engine compartment, in the middle of the compartment, or behind it? Is the underneath of the engine soaked or is it primarly in the tranny area?

How did the vehicle run prior to your plug and wire change? If you put the habeous crankous on the plugs, or dropped one before you put it in, you may have cracked the insulator. That will reap havoc. It isnt easy to f'up a plug, but it can happen. Re-learning your computer is an excellent idea too.
 
Osprey413 said:
Well, today my Jeep ('97 4.0L) has hit an all time low. Let me begin this story a few months ago. In July I changed my spark plugs and wires just as basic maintenence. Install went fine, made sure I put all the wires on the correct plug (by changing one plug and wire at a time). Started engine, idled rough for a few seconds then evened out. Fine. Put my tools away, came back to Jeep and tried to start it. Nothing. Turned over, but didn't start. I took the plugs out and replaced them. Started up with the new plugs. This time I decided to drive over to the mechanic incase it wouldn't start again atleast I wouldn't have to tow it. Sure enough, got it to the mechanic and turned it off. Tried to start it and nothing. The starter didn't even turn the engine over. So the mechanic comes out to look and wigles the battery wires. Engine starts now, but idles and drives like crap. It seems to be missing randomly. Mechanic's theory is that I have water in my gas. OK, I try this theory out. I go through about 20 tanks of gas and I still have the problem. Then, all of the sudden, I get a check engine light. When I got this check engine light the engine had stalled because the RPM's dropped so low that the engine died. Fight with the Jeep the whole way to the mechanic, I had to constantly give it gas to keep the RPM's up. Mechanic looks at it and changes the CPS. The Jeep runs now, but I still have the same rough idle/missing while under gas problem as before, but in addition to those problems the Jeep doesn't like to start in Park unless it is warm. Recently(past few weeks) I have been getting a check engine light weekly. I take it to AutoZone and have them check it out, same problem. The code is for the CPS or CKS. I decided not to change the CPS because the check engine light magically went away after 2-3 starts. Still idles/misses like crazy and apparently at random intervals. I can drive the Jeep one time and have it not miss at all and then the next day barely be able to get out of the driveway. Now, to add to all these problems I have a really bad oil leak. This leak just showed up out of no where. And as far as I can tell the oil only leaks when the engine runs over 3500RPM for an extended period of time (ex. hard acceleration or passing). The leak is so bad that it is dripping down onto my exhaust and smoking like crazy. I even stopped by the side of the road and in the 2 min. that I was there a sizable amount of oil formed a puddle under my engine. But, if I keep the Jeep under 3000 RPM for most of the drive the oil doesnt seem to leak at all. I got home from a 30 mile drive (engine missed alot) and parked the Jeep. Left it running and there was no oil (as far as I could tell) leaking at all. The oil pan had oil on it from the previous leak, but there weren't any drops forming at all. Apparently I have a leaky seal that only leaks at high RPM's. I havent located it yet because this just happened a few hours ago. I am at a complete loss as to what is making my Jeep run so terribly and now with this oil leak I am really distressed. I have no idea what is going on with my Jeep, but it's bad real bad. Any suggestions, ideas, donations, sympathy would be greatly appriceated. Right now I'm in college so I don't have the money to fix these exspensive problems (CPS is $123, and the oil leak will cost an arm and a leg to fix im sure). I love my Jeep and don't want to give it up, but if I can't figure out or pay to fix these problems I may have to sell it and go with a Jap. sedan (the horror). This is how bad of a situation I am in. Please!! Help!!
Click to expand...
You might also follow your battery cable back to where it connects to the ignition module, check for tightness and corroded connections. Just a thought.
 
Well thanks for all the ideas. Basically the plugs have been changed twice since this happened and the wires have been changed three times. Still no improvement. I did not change the distributor or rotor, but I don't really think those are the problem. The fact that the miss and idle is completely random makes me think there is a sensor going bad or there is a wire loose somewhere. I already tried the battery terminal idea, I cleaned both very well. The computer still throws up the (P1340 I think was the specific code) that says "temporary loss of CPS or CKS". But for some reason these codes just go away after a few starts. I suppose it could be a faulty connection somewhere in my wiring harness, but that will be nearly impossible to pinpoit. The miss doesn't act like a bad CPS sensor though because when those go bad the miss more when they are hot, and my Jeep seems to do the opposite. It seems worse when it is cold and better when it is warm. It also misses alot more when I am driving on bad bumpy roads. That also leads me to believe I have a loose or faulty connection somewhere, but I don't know how to pinpoint it.
As for the oil leak, the oil pan is pretty much soaked on the passenger side. Everything else behind the engine is soaked to just from splatter. From what I can tell the leak is somewhere behind the oil filter. It isn't coming from the oil filter, I checked that already. It may be the rear seal, or it could be the seal around the oil pan. I guess either won't be too bad, especially since if it is the oil pan that can be replaced without even moving the engine or tranny. My mechanic said that to replace the rear seal on my '87 (which has a rear seal leak) that he might have to remove the engine or tranny. Is there some way around this? If so, around what price should I expect these repairs to cost? If in fact the missing is due to a faulty or loose connection I can fix that myself with some saulder and electrical tape, but I don't feel confident enough to tear into the insides of my engine. Thanks for the advise.
 
If the fault gets repaired or goes away by itself (intermittent), the ECU clears the code after three (or five?) complete start-run-stop cycles.

How's the wire from your CPS? Could it have been burned by the exhaust manifold and be intermittently shorting out?
 
No, the wire from the CPS is fine. Jeep was smart enough to shorten the wire on the newer models so that it cant reach the headers. I can even wiggle the connecter while the engine is running and it still wont miss. I'm at a loss.
 
you did a tuneup and did not change the cap and rotor ? Just the plugs and wires ? The cap and rotor also wear out. Maybe it's just me but I consider all those parts as wear items and generally replace them yearly at the same time.
Before I started throwing a bunch of stuff at it I would go back to STOCK OEM DEALER SUPPLIED plugs, wires, cap and rotor. Then I would see what I have from there.
 
Sounds to me like the CKS... aka camshaft sensor... is intermittent. This is located in the distributor. Contrary to what has been mentioned above, DO NOT turn the distrbutor. it will accomplish nothing but to make your problems worsen.


When the signal from the CKS drops out, the computer goes into what is called non-sequential mode. this is the reason for the running rough. instead of the injectors firing one by one as needed during the intake stroke (sequential mode), they all fire at once in smaller amounts puddling the fuel behind the intake valve.


At any rate, get the CKS replaced, the battery terminals cleaned, the tps checked and all should be good.

The oil leak is most likely either the oil filter adapter o-rings and/or the oil pressure sender. Not a big deal. happens to every 4.0 eventually.
 
... wouldn't even turn over

... the mechanic wiggled the wires and it started

... runs worse on bumpy roads

I would be concentrating on the battery ground or engine to firewall ground strap. Possibly the primary +12 circuit. Focus on the area of the vehicle where you were swinging elbows and snagging wires with tools and fingers.

ground wire

ground wire

ground wire
 
Yep i'll agree there... possibly a bad or loose ground

There is a gang of ground wires on a stud, on the block just below #5 spark plug area...
 
OK, ill check the ground wires. I don't think the '97 has a CKS, or atleast Haynes doesn't think so. I thought the purpose of the CKS was to take the place of the distributor since the newer models had distributorless ignition. I tried going back to the old plugs before but still no good. I couldnt go back to the old wires becuase one ripped in half while I was removing it. I may try replacing the distributor cap and rotor, but i would think that if those were bad that the jeep would miss consistantly, not randomly. I'm going home from college for the weekend so I will have more access to tools there. I'll start going through all these ideas when I get there. Hopefully the oil leak wont be expensive and I can hopefully pinpoint and repair this missing problem.
By the way, I forgot to mention that when the engine misses I can hear a sort of hiss from the drivers side of the engine compartment. Maybe air rushing in to a vacume point? or maybe a leaky injector? i dont know. as far as i can tell all my vac. hoses are fine.
 
There's a camshaft position sensor inside the distributor - at least on the HO (91+) 4.0s. This is the only electronic thing in there other than the rotor.
 
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Check the battery wires. Pos and neg. Since it is a random problem, it ain't the spark plugs, wires, rotor, or cap. It is probably the camshaft position sensor, the crankshaft position sensor, or the CKS, whatever that is. It also ain't a vacuum issue, that would be consistent.
 
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