cmill91xj

Hey guys! Long time lurker of the fourm. I'm on my 3rd xj now and this fourm has been my go to place for a while now.

Just recently I had picked up a 96 xj and the engine light came on. Didn't have it checked out, but I put in new spark plugs and it went away. The other day I went for a drive(about 80 miles one way). When I pulled back into my driveway and the engine light had come back on. Decides I better check out the light, went to plug in scan tool and oddly enough I could not find the obd-2 port anywhere. No big deal. Turned the key of and on a few times and got the following codes. 12, 43, 43, 55. 12 and 55 I know aren't important. The 43's confuse me. I know it's a random misfire but where do I go from here. Rotor, cap, wires for sure, but what is the deal with the dreaded code 43, valve spring problems?

Thanks in advance!

freegdr

Clear codes and drive iff light comes back on recheck should never double codes ?

tjwalker

You have an OBD port on your 96, must have just missed it. Under the dash near your left knee when sitting in the vehicle.

Use a code reader or scan tool to check codes. The 2 digit code that you got with the "key-on, key-off" technique is helpful, but not nearly as helpful as the full PXXXX code that you will get with either a scan tool or a code reader.

Then go from there. Gotta use the full codes (for 96 and newer) for clues and guidance. Good luck and keep us updated!

BTW, code 43 for an XJ is this: Ignition Control Circuit. Peak primary circuit current not responding properly with maximum dwell time

cmill91xj

Alright so upon further inspection I found the obd 2 port and I'm throwing P300 P301. Random misfire and misfire on one. So new cap rotor and wires should fix right?

tjwalker

It's certainly the place to start as you need fresh tuneup hardware anyways. So definitely go ahead and install those items, clear codes and see if/what comes back.

But that P0300 (random misfire) may be caused by something else. There are a few possibilities, but I usually start by verifying fuel pressure. 96 was a year of change for the fuel system, so the fuel pressure spec. for yours could be either 31 psi at idle (old fuel system) or 49 psi at idle (new fuel system).
Must be verified with a fuel pressure gauge, which can often be rented inexpensively from many parts stores.

Here is a link to more on the P0300.

http://repairpal.com/OBD-II-Code-P0300

Good luck!

cmill91xj

Thanks for the input! I don't know if this is important but I got a buddy that works in the garage at Walmart and he had talked me into a fuel injection cleaning service. Kind of similar to seafoam. Could this have freed up some carbon and cause the misfire?

JeepingDan

I've had these po300's in my shop.
Sometimes a good valve cleaning does the trick.
I usually got the stuff from the dealer.

tjwalker

If you're going to do a top end cleaner, I agree with Dan and recommend Chrysler CCC (Chrysler Combustion Cleaner). It works better than Seafoam. You may need more than one can and follow the instructions on the can closely!

cmill91xj

Ok guy's, sorry for the lack of updates. I've had some family issues come up and haven't had time to mess with the jeep.

Today I was able to get a fuel pressure gauge. Turns out I'm at about 32 psi. I know that's not good, where should I go now?