Hello,I just bought an XJS V12 convt.It starts right up but idles rough has pretty good power but blowing black smoke from tail pipes even at idle.I checked two of the spark plugs and they where carboned very bad one was wet and smelled like fuel i did an oil change and the oil was diluted with gas,Could this be due to either a bad fuel injector or a bad cylinder not firing and the fuel going past the rings into the oil?
Obviously, fuel and oil should never be in the same spot at the same time. You have a dead cylinder and maybe a stuck-open injector. The black smoke is from a too-rich fuel mix, so the cheap things to look for are in the fuel injection system. Look at the fuel pressure regulator as well. Good luck, and don't forget to relieve the fuel pressure before you do any work on fuel inj. engines!
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Check the fuel filter(s). Your long drive may have shaken dirt or old fuel gunk ("varnish") loose and plugged the filter most of the way. Enough fuel gets by to start the engine, but then it starves when you put it under load.
www.jagbits.com/jaguarsensor.php FITS: 1993-1994 6.0 XJ12 AND 1989-1993 V12 XJS FROM VIN 157118 ON, 1994-1996 6.0 V12 XJS FRONT DAMPER .... LNA1622AA - MAP SENSOR ... C42166-USED - USED SENSOR COOLANT TEMPERATURE FOR FUEL INJECTION
www.jaguarforum.com/showthread.php?t=54266 Mar 3, 2013 - I recently bought a 1993 6.0 V12 XJS and when it is started from cold it runs ... to 1300 RPM so it wants to surge forward when braking which is strange. ...Classics · XJS 3.6,4.0,5.3 & 6.0; 6.0 V12 XJS High RPM When Warm ... You might want to adjust the aux (extra) air valve to bring the idle speed down.
Hi Gina.... Rough idle could be a number of things. The easiest and cheapest thing you could do is to replace the fuel filter. Usually they will run just a few bucks at the local auto store. If that doesn't do the trick, try to see if your car is smoking at all and try to determine if it is blue, black, or white smoke. Usually a blue smoke is oil, black is usually fuel richness, and white is coolant. White and blue are the most serious. If you are just burning extra fuel, you might need a tuneup consisting of new sparkplugs, maybe new sparkplug wires, new distributer cap, and distributor rotor. This might be a good time the change the oil and oil filter as well as check the other fluids such as transmission, coolant, and brake. Joe
oil sending sensor could be bad. I know a few different type of cars have trouble with the oil sending unit. They all pretty much do the same thing, "oil light comes on at idle and goes off as you drive". But on the other hand it could be a little more serious.