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00 XJ running terribly with lots of codes.

1

123Grains

NAXJA Forum User
NAXJA Member
Location
USA
Let's start with the basics. 00' Jeep Cherokee 4.0 Auto with California Emissions. The one with pre-cats and 4 oxygen sensors. The engine is a swap with about 140,000 on it.
Okay everybody, I have a fun one for you. My XJ has been running a little rough for the past few weeks and has gotten progressively worse. When I started it today it was chugging pretty badly so I decided to go on a little test drive and cancelled my plans for the day. Well, I didn't get very far. After about a mile she would barely move. Very little power under load. If I gave it more than 40% throttle it would start backfiring, chugging terribly and flashing the CEL. I had to limp it home, going uphill was an arduous task that barely moved the speedometer. I hooked up my scan tool and got a pile of codes. P0300, P0303, P1494, P0306, P0161 and a pending p0305. P0300 - Random Cylinder misfire. P0303 - Cylinder #3 Misfire. P0306 - Cylinder #6 Misfire. P0161 - Bank 2 Sensor 2 Oxygen sensor heater performance. P1494 - EVAP leak detection pump pressure switch condition. P0305 - Cylinder #5 Misfire (PENDING).
Any advice would be greatly appreciated. I'm going to attack the oxygen sensors tomorrow since I have all four in my toolbox and I'm hoping this will clear up the issue. I have no coolant loss so hopefully it isn't a cracked head. Considering that it was so sudden, I doubt that it is the problem. You have to love those 0331 heads. :doh:
 
I forgot to add that up until now whenever I gave it throttle, it would clear up and run better until about 3,000 RPM. Now it just runs terribly no matter what the RPM.
 
Test the coolant temperature sensor. Check the O2 sensor fuses and wire harnesses. Test O2 sensor function.

Otherwise, ignore the 0300 codes and solve any other codes. Always start with lowest trouble code number. Higher number trouble codes are often caused by poor running or faulty sensor data related to the lower numbered codes.
 
I hadn't thought to test the coolant temp. sensor but I will once I have daylight. I'll check the fuses, harnesses and O2 sensors while I'm at it. Thank you for the suggestions, I'll let you know how it goes.
 
The thought of a plugged cat had crossed my mind as well. It just so happens that I have one from my previous XJ that matches this one and has no miles on it. Wish me luck, I'm tackling it in a few hours.
 
The Google knows everything. For 2000-01, I prefer Autolite APP985 or Champion 7034 (which are both double-tipped platinums), or Autolite XP985 (Iridium). Avoid installing any single-tipped platinum plugs like the Autolite AP985 or Champion 3034.
 
Everything I have seen says Autolite APP985 and *no* AP985. It used to be simple when Champion made the Truck & SUV plugs. Now you need copper core or double platinum, iridium, etc. and stay away from Bosh when it comes unless its the fuel pump.
 
After running in to loads of issues like this, for most people it was either a bad injector which can be tested by simply swapping them around and seeing the issue chases the move or not, a bad CPS, or a cracked head/blown head gasket. My suggestion is to start with diagnosing for low compression, and if that all passes, then go on to the cheaper things. But, often enough people waste money throwing sensors, injectors, plugs at something just to realize they spent $200-300 which would have been spent on fixing their head problems.
 
Okay, guys. I finally had time to install the parts that I had hanging around the garage. Which included four NTK oxygen sensors, Walker direct fit cats, New coil pack, and six new Champion double platinum plugs. We still have a dead skip on cylinder #3 & #6 but no more backfiring. Still has very little power and runs terribly. I put a fuel pressure gauge on it and it is fluctuating between 40-45 lbs at idle. Now we have a step in the right direction. Any thoughts?
 
Check the fuel pressure while driving. Fuel spec is 49 + or - 5psi. The 40 psi is a bit low, but I would perform other diagnosis prior to pump replacement. You should have just gone with copper NGK plugs though.

Oh.. after you did all those changes did you reset the PCM?
 
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