Hi all - first time poster. Sorry for the novel, but I'm hoping someone can help.

I bought a 2003 XJR with about 97,000 miles on it from Florida and had it shipped to Colorado. The car came to me with the CEL on. PO said the CEL was due to a missing DTC Definition that was accidentally erased when his mechanic cleared previous codes.

I took the car to an emissions test and it failed due to high NOx. Everything else (HC and CO) was well below the limits. I decided to check the codes and it came back with P1647 (O2 Sensor) and P0332 (Knock Sensor). I replaced the bank 2 upstream O2 sensor and cleaned the harness connection for the bank 2 knock sensor (the few posts said this was a common problem). I also did an oil change while I was at it. I did a hard reset and drove the car for about 50 miles and my CEL stayed off.

Took the car for emissions a 2nd time and it failed due to high HC readings (3.9 GPM and the limit is 1.2 GPM). This time CO and NOx were below the limits. The car runs very smooth (no misfire or knocking). I decided to replace spark plugs anyway since high HC readings indicate unburnt fuel. I also cleaned the MAF sensor.

Took the car for its 3rd test and it failed again with similar results. HC was at 2.9 GPM. CO and NOx were fine. I wasn't sure how long the PO drove the car with a bad O2 sensor and since I plan on keeping this car for a long time I decided to take the car in and have the cats replaced. While I was at it I had the muffler shop delete the smaller resonators and add a crossover pipe. With the new cats in, I did another hard reset and drove another 50 miles.

On the 4th test the car failed HC even worse. This time it was at 9.0 GPM. Not sure where to look now. Still no CEL to indicate anything is wrong.

I just got done checking fuel pressure and that checked out fine: ~40psi without vacuum, ~45psi with vacuum. I also checked for vacuum leaks by spraying some MAF cleaner around the vacuum lines and intake. There doesn't seem to be any leaks but I haven't done a full smoke test. I also dumped a can of Seafoam in the tank in case it's clogged/dripping injectors, but I wouldn't think the car would run this smooth with bad injectors.

Could any of the following not throw a code but result in high HC emissions:

• MAP sensor?
• EVAP system (PCV or CCV)?
• EGR valve?
• MAF sensor?

If it helps, the diagnostic report from my last test shows the HC skyrockets about 10 seconds after acceleration and stays peaked until about 10 sec after deceleration. Also, my LTFT reads about +4 to +13 throughout the test. My STFT reads mostly in the negative (as high as -19 during the test). Not sure I understand this. Seems like the car is adding fuel to compensate for lean readings in the long run, but subtracting fuel for rich readings in the sort term.

Hopefully someone here can make sense of this! Thanks

 

Welcome CVP, please take a few moments to introduce yourself in the New Members Forum, top left task bar, ...Forums, ...General Jaguar Forums, ...New Member Area....thanks.

Accidentally erased, umm....yeah, sure. Since we don't have inspections in FL, the PO probably drove it with the light on and the thought of "hey, ...its running great, I'll just ignore the light", which may have caused additional issues over time.
Have you tried unplugging the MAF (the ECU will go into default on trim levels and allow the car to idle and drive casually), so you can tell if it may be the culprit?
I am suspect you may have a code on the verge of throwing, ...perhaps the other upstream O2? Do you get a code 1000? That's the ECU not completing a cycle check, which may be your problem which hasn't tripped yet.
There are a couple of folks on site who could determine if its the VVT. I am not knowledgeable enough of that and hope they can chime in to assist.

 

Have you checked the PCV valve to see if its clogged?

 

You have an engine with 2 banks thus 2 LTFTs, 2 STFTs, etc.

I'd start with using OBD live data to read those. Get engine hot then park. Read at idle and again at 2500 or so rpm.

The same tool can show exactly which OBD monitors are unset (incomplete).

An elm327 will probably do. Very cheap.

 

with an 03 and that miles -- my guess is the compression is OK. Have you checked the intake for any leaks -- the accordion can crack. What type of cats did you install?

 

See my posts to get some possible insights:

https://www.jaguarforums.com/forum/x...r-what-178651/

 

I would love to see the LTFT for both banks. But I would guess it is a bad MAF sensor. Try cleaning it and then check the for vacuum leaks in the air tube through throttle body . . .

 

+ 1 on the MAF/Connector...

 

Sorry for the delayed reply. Here's an update from the feedback received.

Got the car up to operating temp and checked the trim levels. Here are the results:

At Idle:

• ST B1: -8.6%
• LT B1: +17.2%
• ST B2: -9.4%
• LT B2: +14.8%

At 2500 RPM:

• ​​ST B1: +12.5%
• LT B1: +0.8%
• ST B2: +9.4%
• LT B2: 0.0%

I do get a P1000 code on the reader, so I'll continue driving around to get the ECU to do a full cycle check.

The part load breather is clear (I'm assuming that's what jackra_1 meant by the PCV valve).

I did unplug the MAF sensor and the engine stumbled a bit, then threw some codes related to that. Don't know if that means anything about how the sensor is functioning.

 

The P1000 will throw until the issue is resolved....that code is simply the ECU's inability to complete its sensor checks until the issue's fixed. If your clearing your codes and the P1000 doesn't clear, try clearing again. Using my ELM327, I have found that the P1000 will remain initially and I have also found that by running a second clearing, it removes it and you can see if the ECU will complete a cycle (meaning a possible intermittent issue) or immediately return and a hopeful solid code.
Yes, the unplugging of the MAF will throw a code and thus the ECU goes into default for that sensor. You will need to clear that again after reinstall of the MAF plug.
This site is very good... JagRepair.com - Jaguar Repair Information Resource ...to book mark and the following links are from it.
... http://www.jagrepair.com/images/Auto..._2001_OBD2.pdf
... http://www.jagrepair.com/images/Auto...ent%201998.pdf
... http://www.jagrepair.com/images/Trai...20-%202000.pdf

 

Those idle trims look like it's still (re)learning. More driving (or idling) and see what they do.

 

Quick update - car passed emissions today. I decided to go ahead and replace the MAF sensor and the bank 1 upstream O2 sensor. When replacing the O2 sensor, I discovered the exhaust shop reversed my O2 sensor locations by mistake. My upstream sensors (gray connectors) were installed in the downstream locations and vice versa. That explains why my emissions were worse after the new cats were installed. Thanks for everyone's feedback and help!

 

Please that it worked out; even more pleased when someone reports back: that is how we learn, especially on old cars.

 

What a nightmare!

Good you found it and it's back to OK.