UPDATE: 1996 Jeep GC multiple misfires, hesitation and bucking (Tranny question)

Here is my original post and thread for a complete history, but I have a new twist.

http://www.automotiveforums.com/vbulletin/showthread.php?t=503585

I now have a new more serious question as I still try to figure out this ongoing "misfire" problem. I am beginning to think that the "misfire" code may actually be a "phantom" code because it happens so randomly and almost never occurs if I drive around town at or below 60 mph.

In the course of my troubleshooting, I discovered that my tranny fluid was really low. I followed my Haynes manual to be sure I was checking it correctly, read a lot of posts about low tranny fluid, possible symptoms and fixes and see that this "may" have been the cause of my current problem.

So, I decided to level it off and try to reproduce the "bucking" at 65 mph or higher that would eventually gave me a 43 "misfire" code on my digital odometer. Even if it didn't fix my current problem, levelling off the tranny fluid needed to be done regardless (The fluid did not smell burned and wasn't bright pink like new fluid, but it did have a pink tint to it).

Now, here's the problem.

I didn't look at my owner's manual before I added fluid and I added Dex-III. Now it seems that since it is not ATF +, that I have screwed up. I didn't stumble across this as incorrect until I read a little deeper on some tranny problem posts on here.

However, the good news is that when I levelled off the tranny fluid, the Jeep drove like a dream for about a day or so. But now I am getting "bucking" symptoms again (above 6mph and you can observe the TAC noticably "bouncing" around the 2000 mark before it "bucks"), but no CE light and 43 code yet. What I don't know is if this could be as a result of the Dex-III fluid not being the right fluid or still something else altogether.

What is puzzling to me is that the Jeep drove great after the intial fluid add, better than it has driven in weeks. Maybe I'm overthinking this and should just change the CPS again to a MOPAR part as I have stated in the earlier thread.

So, what do I do now? Changing the tranny fluid to ATF-4 (I'm guessing from what I've read would be the correct type) has to be cheaper than a new CPS. Should I have the bands adjusted too and give it a whirl to see if my problems go away?

REALLY need some help with this one if you can...

Thank you.

Bryan

Your problem is not in your trans. You added how much Dex? It is ok to top of with Dex. The ATF+ fluids have friction modifiers that help TCC and harsh engagement but that's about it.

As far as your skip goes, start from scratch and go over all of your secondary ignition components. If you can isolate a particular cylinder causing the problem by doing a power balance test.

Altho there are many many problems in jeep trannys when you use Dexron/Mercon tranny fluid, it is safe to use it to top the fluid level off (heck it does say to use Dex on the tranny dipstick anyways). Have you searched back through the forum, I know there has beena few cases of this, maybe you will find the solution.

I ended up putting about a 1 to 1/2 quarts of Dex-III in. I think when I measured it a few months ago, I did it wrong and got an incorrect level, therefore I had to add much more this time.

No sign of leaking at all and I measured the level just now and it's OK and at the same mark as I expected. I'm due for a change anyway, but I added the fluid just run some tests and obviously it didn't work. So it won't hurt.

However, driving home today (about 10-15 miles) the TAC was really erratic around 2K (Of course, making a complete liar out of me with regard to the <60mph smooth driving thing, but usually it is highway driving that causes the "buck"). No "bucking" and no CE light at this point, but it was clearly struggling more than usual at lower speeds.

Regarding the cylinder misfires, I had a dealer mechanic that I know check it with thier scanner and it throws codes for all of them eventually. This was early on in the process, but the symptoms are still exactly the same.

I've now had changed, or changed myself, the CPS, TPS, Ign coil, plugs, wires, cap, measured the fuel pressure (only at idle, 50psi), cleaned the throttle body, added Seafoam to the fuel (today).

I go back and forth all the time from fuel to CPS to tranny to PCM to just about anything at this point. It's a tough one to diagnose.....and repair shops have been no help...

Thanks for the help.

Bryan

Anybody got any feeback on this post from "protozee"???? (Link included, but text is below also)

http://www.automotiveforums.com/vbulletin/showthread.php?t=156852&highlight=fuel+filter


The jeep shake or shudder, misfire may occur when the vehicle is operated between 50 - 70 MPH

I tried 2 jeep dealers and they could not fix this, one said it was the coil, replaced it no help, and tune up, injectors cleaned too no help. The other on said it was the torque converter and pump it was under warranty, no help. So I think they just want to sell you something or they don’t know any more then we do, or maybe they throw the service bulletins away. So I did some research on the internet and this is what I found the trouble. So far
I have paid a lot of money at the dealers.

Late closure of an exhaust valve may be the result of no valve rotation and associated build up of carbon on the exhaust valve stem.

So I bought a 16 oz. bottle of Marvel Mystery Oil, put half in the gas tank and the other half in the oil. No more jeep shake or shudder or misfires.

By the way the $500 at the dealer for decarburizing



4.0L MULTIPLE CYLINDER MISFIRE
Date: 08/01/03
Model Year(s): 1999-2004

Description: NOTE: THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH A 4.0L ENGINE. This bulletin involves inspection of all engine exhaust valves and a decarbonizing procedure if necessary.

Details: The customer may experience an incident of engine misfire during certain vehicle operating conditions. The misfire may occur when the vehicle is operated between 50 - 70 MPH and under light loading conditions, e.g. slight uphill road grades. This condition may occur at all ambient conditions, but is more noticeable when ambient conditions are less than 0 C (32 F).

If the vehicle is equipped with On-Board Diagnostic (OBD), a MIL illumination may also have occurred due to Diagnostic Trouble Code (DTC) P0300 - Multiple Cylinder Misfire. Various single cylinder misfire DTC?s may also be present. If the frequency of misfire is high the Powertrain Control Module (PCM) may place the engine in ?Limp-In? mode.

The misfire condition may be caused by one or more engine exhaust valves that are slow to close. Late closure of an exhaust valve may be the result of no valve rotation and associated build up of carbon on the exhaust valve stem.

This condition may occur when the engine is not allowed to run at engine RPM?s that are greater than 3,200 RPM. At 3,200 RPM or higher the engine exhaust valves will rotate if not impeded by high carbon deposits. Low engine RPM?s and high carbon deposits are associated with short trip driving where the vehicle engine is not allowed to fully warm to normal engine operating temperatures. Cold ambient temperatures will increase engine warm-up time and add to the opportunity of carbon deposit build-up on the stem of the engine exhaust valve.

OK back up and stop :banghead: You said you replaced the cap I'm assuming you put a new rotor in there too correct? The key here is to isolate the cylinder that is giving you a misfire. Is the check engine light on?

We put in Champion plugs. We also put on better quality wires and dist cap (MOPAR Kit SPC40604AA) that my original mechanic did not use. We thought that poor parts may be the original cause, but it wasn't. Nonetheless, I have new plugs, wires and cap.

Bryan

Plugs, wires, cap ........

You said you replaced the cap I'm assuming you put a new rotor in there too correct?

Rotor?

rotor button, inside the distributor cap. It connects tothe distributor shaft and spins with the distributor shaft, this is the part that actually sends the spark to each of the plug wires....

Are you saying you think he has a bum dist cap? (even though new)

OK..some new info to throw around...

I tried something different today to see if I could induce the problem quicker at higher RPM's. So, I decided to drive to and from work without the OD on. On the way to work, there were only some hints of trouble but nothing major. On the way home, my CE light finally came on again (probably as a result of numerous "misfires" over the past few trips and this was nothing new, it always eventually goes off a day or so later).

However, I kept the OD off and from a dead stop to accelerating onto the highway to get up to 60 mph, the TAC was jumping wildly anywhere from 1500 to 3000 (though understand my car was shifting normally and not "jerking" or "bucking" around wildly in response to the same TAC variations) Then, my CE light began flashing for about 10 seconds.

My question is, when the CE light flashes, does it ALWAYS reflect an emission problem? I have already replaced my Cat Converter during this process and I have not thrown any codes for any emission related components. I'm not smelling any odors either. So now I am more puzzled than ever.

I cut the OD back on and took it easy the rest of the way home. Checked the codes by odometer again tonight (I don't have a scan tool) and still only 12, 43 and 55. Translation, "multiple cylinder misfire", same old same old.

Now what??

Bryan

I actually found a link to the "tune up kit" I had a dealer mechanic that I know install for me early on. I got the kit at cost and he put it on for free, so I said what the hell. As I said before, I expect these MOPAR parts to be good...

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33688&item=8009993156#ebayphotohosting

OK...I'm on board with the tranny not being the problem, just wanted to be sure on the fluid and if anyone had seen this cause intermittment misfire codes. i'm just glad the transmission seems to be functioning fine in all gears.

The crazy thing is that I can drive for days without throwing a code or the Jeep giving me any symptom of "missing" I can usually tell just by the drivability. Some days, it just purrs like a kitten. Some days not. That's why I tend not to look at a mechnical failure like the valve springs.

So, basically I still have to figure out whether it's a sensor (Specifically the CPS again), PCM, wiring, ignition, fuel delivery or a vacuum leak.

Even though I have replaced the plugs twice, should I give them a peek this weekend anyway and see if anything looks funny? What should I look for specifically that would help me track this down?

In review, the thing that continues to stick in the back of my mind is that NONE of these symptoms were there until I replaced the CPS for a hard failure in December (it was completely shutting down the Jeep while driving). That does not occur anymore at all, but now I have this intermittent problem iwht "misfires" to which no subsequent part has even "helped" the problem.

I wish the CPS wasn't such a pain in the a$$ to change, because I would go by an Echlin brand today and do it. I just don't think I can do that myself because of the location.

Any thoughts??

Bryan

I'm a big fan of change one thing and see if the problem is fixed. I mean there's nothing wrong with doing a tuneup kit as regular maintenance but you always want to be careful not to do three things to try to fix one problem.

You're telling us the vehicle was running fine until you did a crank sensor replacement. And then it ran again but now you get code 43. And everything you've done doesn't make that code 43 go away.

I think you're right back to what's up with that crank sensor and maybe it's just not quite in there like it ought to be.

Oh and earlier you asked:
My question is, when the CE light flashes, does it ALWAYS reflect an emission problem?

No. The Check Engine light could go on for any of the things it watches.

http://www.allpar.com/fix/80s-codes.html

Quick CPS question about the Haynes manual for the 1996.

When looking at where my CPS appears to be mounted (in the Haynes manual), mine appears to be mounted like the picture for the 5.2L V8 and not like the drawing for the 4.0L I6 shown above. Does anyone know if this is mislabeled?

Yesterday was the first time I could get a REALLY good look at the CPS mount on the bellhousing with a flashlight and it appears to have some sort of material as a cover on it as well. I cannot see the mounting bolts at all. Does this seem right?

Anyway, I'm going to provide pictures for you guys tonight instead of trying to describe it in words. Something doesn't look right to regarding the "type" of CPS that is on my Jeep. But you guys would probably know more.

Can I paste pictures directly in here? Anybody got any hints for that if not?

Bryan

You gotta use something like photobucket.

What page you looking at in Haynes?

I have a 96 cherokee sport 4.0 with the same problem. i am also a auto tech for 15 years and this problem has whipped my butt and my friends and co workers as well. I have changed or tested every ignition part on the vehicle and still the skip. the only code i get is a tps wich has been changed. Sounds like you have done the same. the only thing left is the carbon on the valve thing wich actualy makes some sense so thanks for posting that info!! Or a bad ground some where. Jeeps have a ground strap from the fire wall to the head or ive seen some to the intake ck that as well seen many problems from theese straps.

Any resolutions to this issue? My 96 5-speed Cherokee is having the same issue. New fuel filter, newer injectors, new coil/cap/rotor.wires and plugs, new exhaust with catalytic converter. load on hills and acceleration seem to be the causing factors. Runs great other than the unpredictible and random light bucking/skipping. I have owned it for about 4 months and it belonged to a mechanic previously who had been going thru it as a long term restoration project. Engine and drivetrain were gone thru completely during that process. I did not notice this skip or buck issue for a couple of thousand miles after i bought it (actually drove it about 2.5 hours home when I bought it largely interstate without any notes of the light but noticible bucking that has developed). There were no changes or issues prior to noticing the issue. actually started as CELs for multiple cylinder misfires that I never really noticed. CELs seem to not be as frequent lately but the bucking or skipping has come to the point of my being able to feel it...or am just more sensitive to it due to the CEL issue that I could never trace.

Have you changed the distributor pickup?
http://www.ebay.com/itm/172574698985/www.ebay.com/ (http://www.automotiveforums.com/vbulletin/www.ebay.com/)

I have not because there has been no indication that it might be bad. Is there something you are seeing that might indicate that it is bad? Are you the E-Bay seller of the part you linked to in your reply?


I am circling around either o2 sensor issues or CPS issues.

I'm not the seller of the part. They can cause misfires and hard starting.

That is something I can explore, however, I have never had an issue starting just intermittant episodes of bucking or misfire under moderate load accelerating or passing, usually.

That is something I can explore, however, I have never had an issue starting just intermittant episodes of bucking or misfire under moderate load accelerating or passing, usually.
Look for a spot you can install a 12V test light on the negative wire from pickup in distributor as someone else cranks the vehicle watch if test light blinks. Erratic pulses would help you pinpoint problem with pickup.
Using a voltmeter a good coil should have appx. 12V from positive to negative with the ignition on. If you have a Haynes or other manual you can also check ohm readings for the coil.