Hello

I picked up my 4th Jaguar a couple weeks ago, a late 2002 XK8 convertible with a coolant leak at the mena connector on the octopus hose. I replaced the hose without any major issue, although it did have a zip tie binding it up like others pointed out on the forum. I did wash the engine with simple green and hosed it off prior to starting the work. While I had things apart I did clean the MAF and throttle body. I ran the engine enough to burn any water and she still ran like a champ as I put her in the garage to start work.

Now for the issue. Prior to the hose replacement, the engine ran as smooth as silk. After the hose replacement she starts right up but now has a rough idle and misfires throughout the rev range.

Codes

P1000
P1646
Misfire codes for all 8 cylinders

Troubleshooting

I have checked all the wires behind the throttle body, against the firewall as best I can having assumed I must have snagged a wire pulling the old hose out. I certainly can't see anything but it is tricky to get back there.

I thought the COPs might be damp after the engine clean so I removed and replaced all 8 plugs and blew out any residual moisture with an air compressor.

I have fitted and refitted the throttle body to MAF hose several times and think everything is sealed up.

I sprayed MAF cleaner at all the joints between the air cleaner and throttle body looking for air leaks and noted nothing.


Based on the fact that the car started and ran perfect prior to the Octopus hose replacement I can only conclude that I messed something up during the hose replacement but certainly can find no signs of damage.

At this point I am hoping someone on the forum may have experienced something similar during hose replacement.

Thanks in advance

Tony

 

There are 2 possibilities based on your repairs and cleaning.
1. The ECM is still damp and causing problems, maybe but not likely.
2. The connectors to the Oxygen sensors has been disturbed and are not working correctly.

Trace one of the wires from the O2 sensor back to where it is mounted. You should find 4 connectors there. Clean and re-seat each one and see if that resolves the misfire. You should clear the codes before re-seating and see if they return.

 

You did disconnect the battery before your started disconnecting everything right ? Try a hard reset also.

 

Thanks for the replies.

• I checked all four O2 harnesses for damage and reseated all connectors, cleared the codes and tried again. No luck and P1646 came back.
• I tried a second hard reset, cleared the codes and tried again. No luck and P1646 came back.
• I completed all steps in the factory shop manual for resistance and continuity and everything checked out fine.

So, perhaps the O2 sensor happened to die at the same time I stared the Octopus hose replacement. Does not seem probable but possible.

I ordered a new O2 sensor and will report back once it arrives and is installed.

Tony

 

I've had this symptom anytime I left a leak in the intake somewhere. One time the TB gasket didn't seat right, but I knew what to look for. But, numerous possible causes.

 

My experience doing the valley and octo hose was quite an adventure. It made sense to do it all at the same time with the intake off of the motor. When I re-assembled I had misfires on all cylinders. Pulled it all apart again to find that i had chipped one of the intake gaskets on the install. I also found that I had neglected to reinsert the frikkin hard line vacume line that pushes into the throttle body. Dumb mistake.
After proper reassembly cleared the codes she runs like a champ. Lots of parts and pieces that have to be right. You will find the fault.

 

Okay, despite the low probability, replacement of the bank 1 O2 sensor has resolved my issue. There appeared to be no snags or breaks on the original sensor's cables so I can only assume it was sheer coincidence that the sensor failed just before I started the Octopus hose replacement.

Thanks for the suggestions everyone!

 

Is it possible that the O2 sensor was already bad and by doing the hard reset, the computer had nothing to go on?

Just throwing it out there.