About a year ago, before I bought the scanner, my 2001 XJ8 was running rough and the dash warning said "restricted performance". I think I looked at a forum, that indicated a dirty throttle body, or fuel pressure. It was pretty dirty, and I cleaned it with carb cleaner, which helped enough to stop the warning, but still wasn't running great. The pressure appeared to be correct, and increased a few psi after turning the ignition off. After accidentally dumping too much concentrated fuel cleaner in the tank, with very little gas, I meant to go straight to the gas station to dilute it, but the engine stalled in traffic on the way there. I was able to restart it, but it wouldn't idle, so I had to keep the rpm's up in neutral, then shift to drive and keep accelerating, back and forth from neutral to drive. I filled the tank with gas, but it didn't help it run. I towed it home, drained the tank, changed the fuel filter, cleaned the fuel rail, and all of the injectors with a 9 volt battery and made an adapter for spray carb cleaner. It didn't get much better, so I bought a snap on scanner.
The codes at that time were PO171 "too lean bank 1", PO300 "random misfire, PO301, 302, 304, 305 "cylinder misfire, PO102 MAF, PO112 MAT, PO328 Knock sensor.
So I replaced the sensors, assuming that was causing the misfires as well, but still not running any better, no codes. I was disgusted, didn't touch it for months. A friend told me to keep running it until I get a code. It took awhile to get, but rescan showed the same cylinders misfiring.
The spark plugs were replaced a few months before all this happened, so I checked them out. The plugs for 1, 4, and 5 were clean like never fired, 2 was a little dirty, but not as filthy as 3, 6, 7, and 8. So I cleaned them, and put the coils from the 4 misfires on the 4 that weren't, no change in running. Rescan shows the same misfires as before, now plus number 6. I was expecting 3, 6, 7, 8 to misfire and not 1, 2, 4, 5. I'm not sure what this proves, but I had ordered a set of new coils already, should be here today. I'm not very optimistic that the new coils are going to change anything.
Is there something else that'll cause misfiring?
There's a ticking noise as well, like a lifter tap. If I remember correctly, it was much louder when I 1st got it home, at some point I added a can of seafoam which did make it better, but it hasn't gone away.
I'm about ready to give up, but my wife really likes this car.
Any suggestions?
Thank you....

 

The "tick" should be thoroughly investigated ASAP to rule out timing tensioner issues which can be fatal. You'll need to remove covers & have a good look, there's plenty of threads here on the forum concerning this.

 

You may have bad injectors. I would send them all for ultrasonic cleaning and flow testing.

 

How many miles are on this car? Did the tensioners ever get upgraded? Verify it hasn't jumped timing before doing anything else.

 

Check STFTs and LTFTs along with fuel pressure.

 

1 cylinder misifring can cause misfires in others. When reading the codes, it maybe helpful to figure out on which cylinder the misfire starts. and how much time there is between that event and other cylinders misfiring. I once had a situtation where I got the same codes after replacing coils, however order changed. replacing the coil on the 1st misfiring cylinder solved the problem. (ended up replacing them all anyway).

 

I would check the timing, align the mark on the flywheel and start there.
remove the covers and use a camera to look at the timing chain/guides, how long since they were replaced?
I had a crack on the top guide /runner before.
I removed all plugs mounted them on a board and looked at the color at night of the spark.
As M.S said to get the injectors cleaned and tested properly.
what is the fuel pressure when cranking at the rail?
another idea is to do a system reset.
all the best Dutchy

 

It has 74,000 miles, and I don't know if anything about the history. Valve covers off, got foam splattered inside the top(over the top cam lobes), and rust on some of the cam lobes.
I guess I should buy a gasket kit, and tear down the motor already. Bummer. I hope its as simple as a blown head gasket.....
Thanks for the advise guys, I appreciate it.

 

Yeah don't give up on her, especially if you have the know how to do things.