I noticed a slight discrepancy in your reply quoted above. I'm pretty sure you meant to say you followed my advice to replace those Jun Kee brand coils and now all was good.

That wasn't it, huh? Well, bummer, I thought we were hot on the trail.

Time to move on to the next possibilities. As previously suggested, check the fuel pressure. Unfortunately, the late models have no provision to physically check the pressure with a mechanical gauge. All you can really do is read out the sensor value with a scanner, and hope it's accurate. The problem there is if the sensor is inaccurate, the computer will happily adjust the fuel pump output to this erroneous signal, totally unaware it's wrong.

One other possibility is a leaking fuel pressure sensor. On the early V6, it's at the aft end of the injector rail. Not sure about later models, but think it's in the same place. You will see a vacuum sense line between this sensor and the intake plenum. If the diaphragm in the sensor is leaking, fuel will get sucked into the intake plenum. Depending where the hose is connected, this could cause one bank to run poorly to due to the excessively rich mixture. Theoretically this should cause some other codes, but some codes are lower priority than others and will be inhibited.

To test for a leak from the fuel pressure sensor, run the engine briefly and then shut it off. Quickly disconnect the hose and look inside for the presence of fuel. It may be easier to access the end which connects to the plenum. If you see evidence of fuel, the sensor is leaking.

 

hi Karl,
is this the transducer on the end of the rail?

[
QUOTE=kr98664;2780464]I noticed a slight discrepancy in your reply quoted above. I'm pretty sure you meant to say you followed my advice to replace those Jun Kee brand coils and now all was good.

That wasn't it, huh? Well, bummer, I thought we were hot on the trail.

Time to move on to the next possibilities. As previously suggested, check the fuel pressure. Unfortunately, the late models have no provision to physically check the pressure with a mechanical gauge. All you can really do is read out the sensor value with a scanner, and hope it's accurate. The problem there is if the sensor is inaccurate, the computer will happily adjust the fuel pump output to this erroneous signal, totally unaware it's wrong.

One other possibility is a leaking fuel pressure sensor. On the early V6, it's at the aft end of the injector rail. Not sure about later models, but think it's in the same place. You will see a vacuum sense line between this sensor and the intake plenum. If the diaphragm in the sensor is leaking, fuel will get sucked into the intake plenum. Depending where the hose is connected, this could cause one bank to run poorly to due to the excessively rich mixture. Theoretically this should cause some other codes, but some codes are lower priority than others and will be inhibited.

To test for a leak from the fuel pressure sensor, run the engine briefly and then shut it off. Quickly disconnect the hose and look inside for the presence of fuel. It may be easier to access the end which connects to the plenum. If you see evidence of fuel, the sensor is leaking.[/QUOTE]

 

#4? Yes, that is the sensor for fuel pressure, providing feedback to the computer. You should see a vacuum line on it. Make sure the inside of the line is dry. There should not be any fuel in it.


https://www.autoreservejaguar.com/ja...ransducer.html


Back to your car, does it have the "pressure relief valve" (item #5)? It looks like a standard valve stem on a tire, and is located near the oil filler cap. It is where you can connect a mechanical gauge to check fuel pressure. Later model cars do not have this fitting, but hopefully your car is in the VIN range that still does. If so, definitely hook up a mechanical gauge and make sure the actual pressure matches the value reported by the sensor, as seen with a scanner.

If your car does not have this fitting, Jaguar specified a special TEE fitting adapter. You might be able to fabricate something similar. See post #27 here:

https://www.jaguarforums.com/forum/s...2/#post1866961

 

Ok, I’m back to my car. That diagram is from the previous v6 but the fuel pressure is ok. And a new air filter cleared up a new code. Initially the misfire codes were from Bank 1 (#1,#3,#5) cylinders. Then Bank 2 (#4, #6) were misfiring. So I think it’s less likely that both IMT valves would fail. And there was no change with new NGK coils. I decided to experiment with new spark plugs of different brands and specs. I replaced the 3 plugs on Bank 2 since that is easy to access. Autolite Iridium XP, Bosch Double Iridium, and Denso Iridium TT. And lo and behold, Bank 2 no longer has any misfiring. In fact, I was able to race down my back road like it was new again. My jag hasn’t able to do that in a couple of years. Only it goes into limp mode when I put it in idle or slow below 30 mph. If I clear the codes it will run great. Only codes are misfirings of #1, #3, and #5.

So I’ve taken off the intake manifold off again. I plan to replace Bank 2 with Bosch Double Iridium plugs.

But I think I have another problem. There is oil around the #5 gasket and inside above and below. I take it this isn’t normal. I didn’t replace the gaskets when I removed the intake manifold but I assume the gasket are to prevent air leaking through the intake manifold.
Also I thought I should take off the IMT valves and look at them. Why not. But when I took off I noticed there was oil around the seals and oil inside the manifold. Is this all not good news? Should I just replace the gaskets and new seals around the IMT valves?
thanks for any wisdom you can share.