P0302 'Generic Cylinder 2 Misfire Detected'.

Was driving my jeep the other day and everything was normal. Parked it in my driveway, let it sit for maybe 30 minutes, started it back up and noticed my Check engine light was on.

Instead of going to advance to get it read i figured i might as well invest in a code reader. Bought an Innova 3040.

Anyways, it's pulling a P0302 code and that's saying it's for a "Generic Cylinder 2 Misfire Detected".

Didn't notice the jeep acting weird or a loss of power or anything like that.

Put a new head and all new gaskets on it about a month or so ago and put about 1,000 miles on it since. Coolant level is staying at the same mark (no disappearing coolant), so i'm pretty sure that's irrelevant.

Any ideas?

Thanks!

Year?

Engine?

joe_peters said:

Year?

Engine?

Click to expand...

Let me update my information so it's accurate. Totally forgot to do that.

1999 XJ.

4.0

Is the 2nd cylinder the second one from the front, or the second one in from the back?

"generic" is simply an indicator by the code reader that it is in generic OBDII mode. It's not read as part of the code description. OBDII specifically assigns code numbers to be common across all makes and models. There are codes that are manufacturer specific and not the same for every car.

Cyl # 2 is second from front.

Clear it and see if it comes back.

Digger87xj said:

"generic" is simply an indicator by the code reader that it is in generic OBDII mode. It's not read as part of the code description. OBDII specifically assigns code numbers to be common across all makes and models. There are codes that are manufacturer specific and not the same for every car.

Cyl # 2 is second from front.

Clear it and see if it comes back.

Click to expand...

Thanks for the information. First time i've ever used/seen a code reader in person. Didn't know that the "Generic" wasn't a part of the actual code. Haha.

Will go clear that code now and see if it comes back on. If it does i'll be sure to post again in this thread.

If that code comes back take a look at your tuneup items--plugs, wires, cap, rotor.

joe_peters said:

If that code comes back take a look at your tuneup items--plugs, wires, cap, rotor.

Click to expand...

Simple stuff first; agree with Joe.

I approach a single cylinder misfire on a 99 in this order:

1. Spark plug (replace)
2. Spark plug wire (replace)
3. Distributor cap (replace)
4. Fuel injector (swap to a different cylinder and see if misfire follows)
5. Internal engine issue. (Run compression test on all cylinders; spec is 120-150 with no more than 30 psi variation)

Alright if the code comes back i'll troubleshoot it in that order. I'll get a compression test done on that cylinder tomorrow. (just bought a compression tester.)

When i put on a new head advance auto didn't have Champion Copper plugs, so i put something else in the jeep that they had. That might be the problem.

Cap + rotor + plug wires were all replaced about a year or so ago. Never touched the injectors.

If it is an internal engine issue, what would be the main culprit to put just one cylinder out of whack?


Have another question and i don't want to make another thread to address it.

My steering box is totally shot. From 9 o'clock to about 3 o'clock is a total deadzone. No steering at all takes place there. Put on a new Track Bar, new tie rod + drag link, so it's not any of that.

I was going to just buy an XJ box, but have read about the durrango box mod. Any idea on what year/make/model/engine durango box would direct bolt into my XJ? The XJ boxes have terrible reviews on the advance auto website. Is there another option?

Here's an update just so this thread doesn't die without a conclusion. '

Compression tester came in today. I unscrewed #2 cylinder plug and took a look at it. Turns out it was only gaped to .006. Not sure how that happened as i clearly remember gaping them all to .035 when i installed them. Pretty sure that was the cause of the misfire. Did a compression test on it just as well to check the engine and it came up to 170PSI. (I guess that head rebuild holds some serious compression. Haha)

Going to clear the code now and see if it returns. Going to buy some champion copper plugs as well.

I prefer NGK V-Power plugs; NGK Platinums for the 2000-2001 per Chrysler.