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Spy Hunter TJ 04-30-2009 03:55 PM

Check engine light/ Cylinder Misfire Code???
Hello everyone, I have a problem with my 97 TJ sport, 4.0, 5spd, 180k miles. Im hoping your feedbacks can help me with:
Heres the problem: Check engine light goes on and off; but for the past 6 months or so it is primarily on all the time. The codes are for multiple cylinder misfire. Usually 2,3,6. (Pretty Shure it was those three) Any ways I have replaced the plugs, cap, rotor, wires, oil etc. (all parts from auto zone but were supposed to be factory replacements)
When codes are reset the Jeep will run great with no chk engine light for a day or so and then all of the sudden the light will come back on and it will idle rough and feel as if it has a loss of power, then at random the light will go off and the jeep runs great for a while.
I have had a shop look at it and about $600 later I had a new fuel injector installed. The light still came back on 20 mins down the road. Further research says maybe a bad distributer? Crankshaft position sensor? (Has anyone replaced theyre fuel filter, is that common?) 02 sensor? Computer? Kinda dont know where to go next?? Thanks for your advice...

Saint101 04-30-2009 07:20 PM

My 2001 TJ was doing the same.
Dose the misfire start just after starting? Or all the time?
Here some of the parts I did. My is running right. Canister Purge Solenoid, Air Charge Sensor, Idle Air Control Valve. I went with dealer ones

Jerry Bransford 04-30-2009 07:54 PM

That's a somewhat common issue for 97 and early 98 4.0L engines due to some having received bad valve springs from a bad batch. It took Jeep a LONG time to discover what was causing all the 43 codes when they finally issued a Technical Service Bulletin to give the repair procedure. Basically you just replace the valve springs and do a combustion chamber cleaning. However, if too much time goes by, the valve seats can sometimes get burned from the problem which means a valve job has to be done to completely cure the problem.

I have struggled for years with this same issue with my '97 though it got dramatically better after I replaced the valve springs. I now get only the occasional 43 (misfire) code which is much better than it used to be.

Prior to that, I had replaced everything I could with no help. Then an engineer from Jeep contacted me after seeing my posts asking about the problem... this was back around 2001 or so. He sent me a "care package" for free which contained new fuel injectors, a new engine computer, fuel injector wiring harness, clockspring, etc. to try one at a time which didn't help either. It was well after that that they figured out it was the valve springs. Just don't forget that it may be beyond the point where valve springs will cure it, you may need to have a valve job done. Good luck. :)

jeeprat 05-01-2009 08:50 AM

Check engine light/ Cylinder Misfire Code
I had exactly the same problem on my 97 TJ . I went to pass a truck and the check engine light came on . To make a long story short I changed value springs ( 2001) and its been fine ever since . I must say though I got no help at all from the dealer and Chrysler would only pay for the springs if the dealer did the install .They wanted to take the head off to do it $1200 . I think the springs came to about $50 . Did it myself in about 3 hours, (had to stop for a beer.) Used compressed air to hold the valves up .

Spy Hunter TJ 05-02-2009 12:53 AM

Yeah I have a tech sheet that explains the valve spring and combustion cleaner process but i put that aside due to the problem being intermittent. If it was a valve problem wouln't it run bad and throw the code all the time? I mean the jeep runs pretty good when the check engine light is not on? Am i thinking correctly??

BALLARDAdams 05-08-2009 02:13 AM

run a trouble code test to see what part is causing the check engine light to flash. I would lay my money on an O2 sensor.
wrangler and chrysler parts on sale

primetime 09-12-2009 12:31 AM

Hi , just one question I have a 2004 wrangler ,what is the yellow light that looks like a little house just obove the temperature gauge for? And should I worry?

6DEVIL16 09-12-2009 10:34 PM

Codes in the Factory Manual???TIMING!!!
Seems like you've spent a ton already for the check engine light. When you have it shut-off for it to reset you will drive 25-50 miles. It then will reset in the computer. Do you have a handheld giving you that code? As far as the crank position sensor. It gives off a High or a Low to the computer. Therefore when it goes, it goes. ON or OFF. Without spending anymore money, look for a Vacume Leak or TIMING OFF!!!!!!!!!!!!! O2 sensor will affect smog and emissions testing not performance like you think. Speed sensor the dummy shift light. ETC. Accordingly.........:banghead:

hexemom 10-11-2009 12:28 AM


Originally Posted by primetime (Post 439672)
Hi , just one question I have a 2004 wrangler ,what is the yellow light that looks like a little house just obove the temperature gauge for? And should I worry?

Primetime: Do you have a stick? If so, it's probably the "shift up" idiot light, telling you to shift gears.

rrich 10-11-2009 01:17 AM

To answer your question - yes, a weak valve spring may appear as intermittent watching the light. At idle and slow speeds weak valve springs probably have no effect, no misfire. It'll show up at the higher speeds, the valve(s) just doesn't close fast enough.

When you reset with a scanner it clears all memory of it. It takes 20+ miles to close the portal so it can catch codes again.

To get the light back on, it has to be a recurring thing, not sure how many times in a row, but several (after the portal is closed.) It may not be enough misfire every time you rev it, or you may not rev it the same each time. That may be why it seems intermittent - it's your driving it the same way that's intermittent.

So yes, it could seem to turn the light on intermittently. But the defect is still recorded in memory.
After I think it's 50? restarts and it no longer happens, it falls out of memory.

As it was said, check for vacuum leaks 'cause it's easy, but I'll put my money on the valve springs.

The reason it runs bad "sometimes" may be the misfire is causing a chunk of carbon to make things worse for a time, then blows out.

Replacing the valve springs in not major surgery, get a friend to help you if you aren't sure.

Please let us know how it turns out - what fixed it.

jvc 10-11-2009 05:35 PM

was experiencing check engine light and cylinder misfire codes
on a 99 TJ SE.

turned out to be a cracked distributor cap.

jamesdeanblvd 10-11-2009 11:14 PM

Mine does the same thing. I cleared the codes drove it and the check engine light came on. Auto Zone checked the code and it had the "misfire" issue. I changed plugs, plug wires, distributor cap, rotor, fuel injector cleaner etc. It then happened again, and when they checked it again it came up as 02 sensor after catalytic converter. They then told me that the sensor can't be the problem so don't waist my money. Now I'm thinking, I should replace them both anyway and see what happens.

mudslinger150 10-21-2009 12:09 PM

how do you get the keepers out if you dont remove the head?

rrich 10-21-2009 01:55 PM

Parts houses have an adapter that goes in the spark plug hole - it connects to your compressor. You position the crank so that cyl is on the compression stroke at TDC - both valves closed. Then air pressure keeps the valve from dropping while you take the spring off.
Then you use a tool to push the valve spring down and remove the keeper. Just the reverse going back together. The danger there is if the air quits and the valve drops, or you didn't get that cylinder exactly on TDC and it rotates while the spring is off. Head removal time.

If no air is available - I've seen it done but haven't done it myself - a length of 1/4" cotton clothesline rope stuffed through the plug hole till no more will go in. Then BY HAND rotate the crank till the rope is pressed hard against the valve to hold it closed. Then remove the springs. Since you are not depending on the compressor, you can take your time - even overnight.
The danger there is leaving some of the rope in. Again, head removal time.

It's quick and easy. The worst that can happen is you drop the valve, then you take the head off. That seldom happens if you are careful.

matthewp85 11-26-2015 09:57 AM

my 01 TJ has a misfire
I just notice check engine light stated P0301 which is cylinder one misfire. I can normally drive my jeep with no misfire but once the engine gets up to temp the check engine light flashes and engine shakes. I changed the plugs but still does it. This week im going to change coil pack rail to see if that helps but if it still does it im going to be lost of words. This is so frustrating trying to find out what's going on.

mhc0116 11-28-2015 07:05 PM

Similar Issue
I have tried changing plugs, used fancy plugs light went away but got a 0174 code now. Switched back to plane factory back to 0306 #6 what

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