Hello All,
I have a 2001 XJ, 4.0, NV3550 with about 225k miles on it.
Runs great, but every couple of months, without any symptoms, I get a flashing check engine light,
which lasts for about 8 or 10 seconds, then goes solid.
The codes I get are P0300, with related P0301, (1st cylinder misfire), etc.
Often different cylinders each time.
I replaced the spark plugs, gapped at .035.
The old plugs were worn, but looked good.
Anyone have any thoughts on this?
Thank you.

 

Lots of things it could be. Does the problem seem to be associated to how long you've been driving? I'm wondering if it's a heat issue.

 

It seems to happen about 10 minutes into a drive.
Engine is at full operating temp, but happens in any weather condition.
The odd thing to me, is that I don't detect any difference in the feel of the
vehicle while these misfires are occurring.
No loss of power, etc, etc.

 

I think all late model xj's throw numerous cyl misfire codes...I think the problem had more to do with the calculation of what it considers a misfire than with an actual misfire. My 01 with the coil rail eliminator still throws numerous cyl misfire codes for apparently no reason. some happen at idle, others happen seconds after a normal startup..clear them and its several weeks before the next batch shows up. Its almost never the same cylinder 2 faults in a row

 

Nope, nope, and just nope. Not even close.

If you're getting misfire codes, there are misfires happening and there is a problem to be solved, not ignored.


10 minutes, so, it's probably heat sensitive. Might be an early warning sign of a failing coil pack. Might be an early warning sign of a failing CkPS (crank position sensor) or CmPS (cam sensor). All of these can be heat sensitive and show intermittent failures.

The really frustrating thing is that it's really hard to diagnose until full failure.

You might want to get yourself a BlueTooth code reader and learn how to collect logs. Look at your long term and short term fuel trim, among other things. Having live logs while you are driving just might tell the tale.

There are a billion of them on Amazon. I spent a bit more and got an OBDLink LX. A bit more money, but the software is FAR better than Torque (a free app that a lot use) and they also have some nice PC software that really opens up your logging capabilities.

 

Thanks, "BlueRidgeMark".
I'll look into all those things.

 

Dirty injectors could be a cause, or carbon buildup under the valves.

Get a can of BG 44K. Add it to a full tank of gas.
Run the tank down to 1/4. Fill with gas and drive that tank to 1/4. See if that helps.

 

Yes, the easy cheap fix first!

But, I was just reminded, there's always this to consider.....

 

I have a 97 cherokee I had a misfire in cylinder 2. Well cylinder 2 finally blew so I replaced the engine and still misfire in cylinder 2. Wat could it be