Engine Running Rough P0135 P300 P302 P303 P1297

Hello Forum, Please help as I only have a few ideas left to check/replace:

My 2001 XJ Limited 4.0L Auto (117,00K) started running rough and stalling on the way home from work on Friday, so I limped it home... It was throwing engine misfire codes so I replaced the plugs with Champion Copper Cores, I replaced the Coolant Temp Sensor (it was throwing code P0118) and replaced the Coil Rail.

After replacing all these parts and clearing the codes, I started the XJ and the idle had no change at all.

It threw the following codes:

P0135 - O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
P0300 - Randon/Multiple Cylinder Misfire Detected
P0302 - Cylinder 2 Misfire Detected
P0303 - Cylinder 3 Misfire Detected
P1297 - Manifold Pressure Changes

I checked the fuses under the hood as I searched in the forum and didn't find anything bad unless one of the relays associated with the O2 sensor is bad. Any ideas??!! Could it be the O2 sensor causing all of this???

Thanks in advance... Beatiful truck... Really want to drive it. :dunno:

First, the 00-01 distributorless ignitions are supposed to use NGK V-Fire plugs per Chrysler.

Did you buy any cheap gas--particularly ethanol--lately?

When you pulled the plugs (before the Champions you just put in), did you take the time to examine those plugs to read their states?

Did you gap the spark plugs or A**ume they were gaped correctly?

The codes you listed--before the plug change or afterward?

If it was ALL the fault of the o2 sensor I would expect it to effect all the cylinders. Do you know when, if ever, the o2 sensor was changed last? Only good for about 80k miles.

Joe,

Thanks for the reply. To answer your questions in order, here goes:

1. No cheap gas. I was getting a P0161 Code and Filled up with 93 Octane; the light went out and then a couple short trips later, my problems started happening.

2. I did read the old plugs. All of them were very dry and had a good read. No white lean condition or anything of the such.

3. I gapped the plugs to FSM gap of .035''

4. The following codes were before: 300, 302, 303; the following were after: 135, 300, 302, 303, 1297.

5. I do not know if ever the O2 sensor was changed. I have only owned this truck 1 month and have spent far too much time under the hood instead of driving.... This particular XJ has the California Emmisions of 4 O2 sensors...

It just concerns me I am getting O2 heater malfunctions and a MAP sensor error..... Plus you would imagine new plugs, coil, etc would have changed something; could it be CPS or MAP??!!

Could be a worn spot or contact corrosion in the harness.

The CPS/CKP crank sensor in my experience is pretty much run/don't run. Some have reported heat/stress cracks in the coil packs allowing them to fire to ground. The cylinder 3 misfire could be heat soak related, search heat soak for the TSB info and factory fix, although having the two mini-CATs is kind of the perfect storm for heat soak.

You can test the synch sensor and MAP with a meter.

Post up what you find.

Check the FUSE in the power distribution center. The heater circuit is fused and a blown fuse can create the P0135.

Fuse is often overlooked. Not sure of exact location but around #15 or #16 I think.

Good luck and let us know what you find.

Would this cause a rough running/no start condition? I'll check again in the light when I get home....

Hello, thanks to Joe and BirchLakeXJ for posting.... I tore down the valve cover and found the culprit after doing a compression test. Broken valve spring on #3 Exhaust Valve.

All of the rockers were tightened by some idiot to the point of breaking tension.... It's sad people like this exist but they do... I have realized that I have a remaned head, so I will order 12 new pushrods and a new spring.... 1 of the pushrods are definitely warped, so I will replace them all.

Any other suggestions? Good compression all across the board except for the cyl with the broken spring; it read 0 PSI of course.

No suprise on the reman head. Those year xjs had the infamous 0331 heads. The were cast wrong I believe and were very prone to cracking.

What about the reman? Are they usually reliable? The only concern I have are the rest of the valve springs as they were too tight as well.....

birchlakeXJ said:

Check the FUSE in the power distribution center. The heater circuit is fused and a blown fuse can create the P0135.

Fuse is often overlooked. Not sure of exact location but around #15 or #16 I think.

Good luck and let us know what you find.

Click to expand...

Anyone know the cause of the PO135 and what causes the fuse to blow after replacement?

Wires for both sensors APPEAR to be ok, but I could unwrap the electrical tape and look at that sensor harness closer.

Captain Obvious here: too much current passing through the circuit is causing the fuse to blow.

Shorted to ground o2 sensor(s)--both sensors have been replaced without correcting the problem, but it wouldn't hurt to test them with a meter.

Bad spot in the harness insulation--lot of work to locate, or you can spend a little money for tools: http://www.amazon.com/s/ref=nb_sb_n...ical+circuit+tester+short+open+finder&x=0&y=0

Right - thanks Cap'n!

The downstream o2 sensor looked like the last installer got some universal one and hacked it int the wires wrong. They had spent a lot of time soldering the wrong wires together. Replaced sensor, problem SEEMS to be solved. XJ seemed to be running a little better.

The engine block ground connection was clean and undamaged.

I used one of those fuses with the little light to tell you when/if it blows.