Hello everybody!
Today has been very stressful. While driving today I was getting engine lights extremely often. I had loss of power, very poor acceleration, the car takes 2-3 times to start from turned off, and "restricted performance. The codes that came up were P0171 (system too lean bank 1), P0174 (system too lean (bank 2), P0328 (knock sensor 1 circuit high input bank 1), P0333 (knock sensor 2 circuit high input bank 2). Now it's my understanding that it would be rare for both knock sensors to go at the same time, so what else could it be?

2001 Jaguar XJ8 Vanden Plas, 230,000 KM / 142,000 MI. I've owned the car since 2011 and have put more money into it than I'd like to admit .

Thank you.

 

Have your guides and tensioners been replaced with the upgraded ones?

 

A few things to suggest - a large unmetered air leak, so check the induction tube, the MAF and connections at the front of the tube, and the tube/throttle body interface. Anywhere air can be drawn in will throw off the mixture and lead to lean codes and engine pinking or knocking, which is detonation, the mixture detonates prior to full compression due to too much air and heat, because its running lean. This will occur over both banks so both knock sensors and O2 sensors will record the fault...

Also, what gas did you fill up with prior to this issue, crap gas can cause issues.

Highhorse suggests timing which can also be another thing to check, but usually comes with multiple misfires on the failed bank. Pull a cam cover to see if this is the case, and don't start the car if you feel this could be the culprit.

 

Have the battery load tested. A weak battery can result in many false codes.

 

+1 on the bad gas suggestion had the same codes after I filled up w/ contaminated fuel a few monthes ago.

Good luck !

 

Thank you for all the suggestions. I checked the battery, it is good. I did the spark plugs today, I changed the oil, oil filter, fuel filter (was a major pain!), cleaned the MAF, and cleaned the throttle body. I disconnected the car from the battery completely and let it sit overnight, started like a hot damn this morning. It drove much better today, but still having a very hard time starting it. It never starts the first time, sometimes a very weak second start, but will mostly start 3rd/4th try. If I drive to a store and go inside for 5 min, it will be hard to start. If I turn it off and start it right back up it is fine. I don't know what else to check.

 

Fuel trims will let you check for air leaks and a lot cheaper than swapping parts in hope.

 

I had lean codes on mine, a quick smoke test showed the intake gaskets and the injector gaskets were leaking/sucking in additional air. I did the smoke test after cleaning the MAF, and checking the "tube: for any leaks.

 

Removed the driver side knock sensor. Thoughts?

 

Apart from the protective sleeve are the wires shot? If not and are flexible, put a meter on them, they should Ohm out at around 200K I think. They only report a fault when the engine 'pinks', so chase the air leak and or faulty MAF. Be careful not to drop the knock sensors as there's a fragile crystal in there (Dilithium....probably )

 

Random thought:

A car that starts well cold but is difficult to start when warm is often due to a failing coolant temperature sensor. But, that would not create the lean codes and knock sensor codes so if you are still getting those codes it's probably not the CTS.

It appears though that in post #6 you said everything was fine now except for being hard to start? If that's true then perhaps it's worth checking the CTS. They are cheap and easy to replace.

 

I haven't been getting any engine lights for quite a few days now, however I'm still having a problem starting the car. I purchased a fuel pressure test kit and I am losing pressure at a very quick rate.

 

What's the mileage on this car?
Has it been serviced regularly?
Starting problems can only be lack of fuel, lack of spark....and in your case
it seems to be lack of fuel.
When it does fire, does it start cleanly or stutter and splutter a bit?
If your pressure test kit shows you loosing pressure rapidly....go to the pressure regulator.
Check when running and with the vac hose removed and test pressure reading....then replace vac tube and test reading.
Do a vacuum test on the regulator....it is probably shot.
You can test by placing a short length of tube on regulator and sucking on the other end....if you can build a vacuum on your tongue, it's working, if you can't, the diaphragm in the regulator is shot.

 

Update: I fixed the starting issue. It turned out to be a bad fuel regulator. Instead of buying a part, I actually found a local parts car and purchased the entire car. After installing the fuel regulator the car has started up everytime time, the first time! However I was still getting knock sensor & fuel codes. I then found out my part load breather hose (the long one on the driver side of the engine) had cracks in it which lead me to believe this was the problem with the codes. I removed the cracked one, removed the good one from the parts car, fitted it in, took the car for a drive and everything looked good! That is until I was seconds from home and the car threw restricted performance. No engine light, but when I hooked up my scanner, sure enough...knock sensor & fuel codes. I currently have the 2 battery cables touching to reset the computer. Any other suggestions?

Thank you!

 

Update: Tonight I was getting P0328 Knock Sensor 1 Circuit High Input (Bank 1).

So I pulled off the entire knock sensor off my parts car and put it on the car with the problem. Drove it and got restricted performance again, hooked up my scanner. Now I'm getting P0333 Knock Sensor 2 Circuit High Input (Bank 2).