Hi everyone! I recently purchased a 1999 xj8 with 111,000 miles and no major issues. I love it!

When I purchased it, I drove it home from NJ to upstate NY, approximately 350 miles. I must admit it was unnerving to drive a 22 yr old vehicle from a used car dealership 350 highway miles as the first voyage! On my trip I noticed it would not reach temperature when moving; only when idling. So upon some research, I figured my thermostat was stuck. I replaced the thermostat and upgraded to the new aluminum housing. Interestingly, the thermostat was not stuck. Someone had cut off the back portion of the thermostat, so it was always open. I'm not sure why anyone would do this. With the thermostat replaced, the car reaches temp perfectly and does not overheat whatsoever. Nevertheless, not reaching temp while cruising delayed the drive cycle, so the catalyst and evap cycles didn't run until just recently. I'm not sure if the evap just finished or it has been finished and just developed a problem, but I now have a p0443 code and I'm not sure where to look. Where is this valve located? The code indicates a circuit malfunction - does this mean the valve is not functioning, or could this indicate an evap leak?

When I did the thermostat housing, I tried all of the tricks of this forum, but I ended up having to lift the intake plenum a bit to access the rear bolts. Being an older vehicle, I'm sure the seals are pretty brittle. I didn't replace them, but the engine appears to run fine still. Smooth idle, no hesitation. Is there any reason to think lifting the plenum would throw an evap code? I don't notice any obvious hissing or flowing air when idling or driving. However, when under the hood, if I manually depress the throttle body, I hear the suction of air for maybe a half-second before it disappears. Is this a normal rushing air sound, or could this be a plenum leak?

Other than this one code and the strange thermostat mod, this car has been wonderful so far. Everything works the way it was intended. There's not a speck of rust anywhere and the paint is superb. Every now and then I experience little glitches. On rare occasion, the information screen will display a traction control/stability control fail at random times and this is cleared when the car is shut off and restarted. It rarely happens and is inconsistent in appearance. I had to replace the speakers as the foam had disintegrated. Intermittently, the driver side speakers (front and rear) only function at a fraction of the power of the passenger side. Again, this issue is not continuous and nor does is consistently present. So I'm convinced these little issues are more likely electronic glitches than total failure of components. I am not sure if the secondary tensioners have ever been changed, but the engine is smooth and quiet and at 111,000 miles, I'd imagine they have been replaced with the upgraded version.

Any suggestions for any of these issues would be greatly appreciated! My biggest concern is the p0443 code, but the others would be nice to resolve also.

 

Couple things to check regarding your evap code. First, have you cleaned the secondary or low flow crankcase breather? It's a known issue with these and the topic of a TSB. Clean it per instructions. Secondly, an evap code is very possibly not the result of a failed component. I replaced everything from my purge valve to the canisters and the code persisted. Turns out it was a combination of that breather and a few minor vacuum leaks. Smoke test the car, both through vacuum lines as well as up the main intake from the engine side of the MAF. Even a very minimal leak can cause trouble.
As for your intermittent ABS/traction control message..... Mine does that too, and I'm sure we are not alone. It is most likely a loose connection in the ABS control module. Easy to fix, I just haven't gotten around to it. Chevy trucks are famous for that as well, and my Chevy van does the same thing. Someday I'll fix both....
-Steve-

 

Hi Reference traction control/stability control fail at random times ..I have had the same issue ... intermittent at first ... but gets worse and more annoying !! ... my mechanic tells me its a front wheel sensor that just needs to be changed (one on each wheel!!) apparently the "computer reader" picks it up ... havent changed it yet !! ... let me know if you change yours and it works ... Great car ... had mine 25 years 1999 XJ8 sovereign.

 

Steve,

I reset the computer and cleaned the part load breather as per the TSB. Interestingly, the TSB states to check if cleaning is needed by holding paper to the full load breather stub with the engine running, and if the paper is sucked to the stub, cleaning is necessary. When I tested the stub, the paper did not get sucked in whatsoever. I cleaned the part load breather anyways. It was indeed clogged with sludge and the drill bit did not move easily at first. After some movement, I removed a decent bit of buildup until the drill bit could be rotated and moved with ease. Upon reconnection, I ran the paper test again, and this time -after cleaning- the paper did get sucked to the stub. This seems to contradict the TSB, but I definitely removed some debris. Once fully reassembled, I manually operated the throttle and heard a noticeably better RPM increase. Less hesitation than before. Have you used the paper test on the TSB and had the results be opposite of what they state? Once the computer finishes the drive cycle, we shall see if the P0443 returns.

 

Make sure you have a good battery. You’ll get weird electrical things occurring and that traction control message sometimes with a weak battery.