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Misfire Cyl. 1

#8
Mine is a 98 and I had this on the number 3 cylinder. I tried everything that has been suggested and it would come right back. After some research I found out that there was a bad batch of springs for the 98s. Solution was to pull the head and have it rebuilt. Did that and, knock on wood no more problems.
 

LBarr2002

LIFETIME
SUPPORTER
#9
Mine is a 98 and I had this on the number 3 cylinder. I tried everything that has been suggested and it would come right back. After some research I found out that there was a bad batch of springs for the 98s. Solution was to pull the head and have it rebuilt. Did that and, knock on wood no more problems.
Valve springs? How long ago did you do that and at what mileage?
 
#10
Check the plug for fouling, or other damage.
I would check the #1 plug wire with a meter.
A redneck wire test is to swap the wire with the one closest to it's same length, and see if the misfire follows the wire.
Check your valve adjustment, and check your mechanical timing.
 
#12
Mine is a 98 and I had this on the number 3 cylinder. I tried everything that has been suggested and it would come right back. After some research I found out that there was a bad batch of springs for the 98s. Solution was to pull the head and have it rebuilt. Did that and, knock on wood no more problems.
There was a bad batch of valve springs from mid 1997 to early 1999 in both 4 and 6cyl engines.
It should have been a recall with the number of vehicles it effected. Instead it's no more than a TSB. The TSB basically states that if you suffer from a recurring misfire after verifying the ignition & fuel systems are properly operating, then it is likely a week valve spring, and the head should be removed for overhaul.
With the availability of tools today, a tech can replace the valve springs without removing the head! No need to perform the expensive overhaul, or replace the head, just replace the faulty parts!
 
#13
There was a bad batch of valve springs from mid 1997 to early 1999 in both 4 and 6cyl engines.
It should have been a recall with the number of vehicles it effected. Instead it's no more than a TSB. The TSB basically states that if you suffer from a recurring misfire after verifying the ignition & fuel systems are properly operating, then it is likely a week valve spring, and the head should be removed for overhaul.
With the availability of tools today, a tech can replace the valve springs without removing the head! No need to perform the expensive overhaul, or replace the head, just replace the faulty parts!
But my luck is like yours sometime, I replace the first one, then another and another. This way I pulled the head took it to a shop and presto a weekend of labor and I'm back on the road.
 
#14
But my luck is like yours sometime, I replace the first one, then another and another. This way I pulled the head took it to a shop and presto a weekend of labor and I'm back on the road.
Don't get me wrong. I didn't mean to replace one. I would always replace them all as a set. I just meant that there's no reason to do more work, or spend more money than necessary.
 
#15
I don't know what to think now... I still haven't pulled the plugs and run a compression test, but yesterday i drove it around for a hour or better and the check engine light went off, It almost seemed to start rough but clean up as it warmed up to operating temp. Would a crank position sensor cause this weird problem?
 

LBarr2002

LIFETIME
SUPPORTER
#16
I don't know what to think now... I still haven't pulled the plugs and run a compression test, but yesterday i drove it around for a hour or better and the check engine light went off, It almost seemed to start rough but clean up as it warmed up to operating temp. Would a crank position sensor cause this weird problem?
The code just said misfire right?
 
#18
If your misfire is mostly during cold start up use a diagnostic scanner to see what the ecm is showing as the engine temperature.
 
#19
If your misfire is mostly during cold start up use a diagnostic scanner to see what the ecm is showing as the engine temperature.
Ok. Ill look at that... I do know i have something wierd going on with the cooling system... i have no heat, but have pretty good flow through the heater core.....
 
#20
I am not up to speed on 4.0L, but Toyota was notorious for having a rubber coolant line at the throttle body that would be a pain in the arse to get out all of the air. And this little bubble of air in the coolant would do screwy things with the sensor at that location that required a coolant temp. Once you burped out the air, it would work great. Not sure that is something that could happen with the jeep motor, but something to think
 
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