Jaguar Repair: 1987 XJ6 Rough Idle, Sputter, and Die, coolant temp, compression gauge

Question
QUESTION: I am the original owner of a 1987 XJ6 with 13,000 miles.  It ran fine until recently.  Now it starts fine in park, but unless I pump the gas pedal, it idles rough, slowly loses RPM's, sputters, and finally dies.  If I start it again and hit the gas pedal raising the RPM's to about 2K, it runs smoothly without missing.  If I start it and shift into drive, it immediately dies.  If I start it, gun it in park and shift it into drive, it will take me down the road, but at much reduced performance, though without missing.  I checked for obvious vacuum connection issues, jiggled the ignition wires, but have done no real troubleshooting.  The fuel filter is original.  I would appreciate your ideas on where to start.  Also, if you recommend a fuel system pressure test, would like your recommendations on where to get a suitable gauge.  Thanks!!

ANSWER: Hi Bill,
All of the symptoms are useless information other than to tell you you need to run tests. Yes, fuel pressure is the first I would run. You need a gauge that can read fuel injection pressures. On this car it is about 32 PSI normal and about 42 PSI with the vacuum pulled off of the regulator. While the regular fuel injection testing gauge is expensive you can just get a industrial gauge that can work with fuel and a "T" and some clamps much cheaper. You need a 12v test light and a volt meter and also a "Noid" light available at most auto parts stores (not expensive). Also get a compression gauge.

First run a compression test even though the mileage is low you don't want to leave stones not turned over when looking for a fault.
Then run the fuel pressure test. Test the Injection coolant temp sensor with the ohm meter. I found that most operate at about 1 K ohms at 63 deg F. and about 100 ohms at 190 deg F. Check every injector wire with the Noid light to see that all are firing. Clip a timing light on each plug wire to see that each flashes the light. Set the timing as per the sticker under the hood.
If everything shows normal (but ONLY after all the tests are run) and it still seems wrong try adjusting the idle mixture and Idle speed after it is warmed up.
Let me know,
Howard

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QUESTION: Howard:  
Thanks so much for the quick response.  I appreciate that.  Well, I believe you have put me on the right track with your suggestion for a compression test before anything else.  The results do not look good.  Both dry and wet tests read the same: #1-130, #2-150, #3-<50, #4-<50, #5-150, #6-140.  I am mechanically inclined and have worked fairly major maintenance on American V-8's.  Is there anything I can do, or must I entrust the next steps to the experts?  Thanks again!!  Regards, Bill

Answer
Hi Bill,
If you had the throttle open on the test of #3 & 4 and the wet test was about the same, it is an indication you have either a head gasket blown between 3 & 4  or both have valve problems. Check the valve clearance on both cylinders and if they are ok the head needs to come off for either gasket or valves. If you decide to do the job yourself let me know and I will give you a few tips that make it different than a domestic engine to do.
Howard