Check engine light

So you are driving along in your XJS on a beautiful sunny day. Not a care in the world, perhaps with the top down and masses of beautiful birds are flying over, conveying from the front to the rear that an XJS is passing below so no droppings permitted as there are consequences. Then suddenly your check engine light shows up and then a very uncomfortable feeling comes over you as if your nerves are being placed in shock. You know the one that a dear may be experiencing when their eyes are met with the brightness of headlights from a very fast-moving car! Well, there is no need to panic because when this light comes on for the first time, it is suggesting something needs attention but not so urgent as to pull over and end this great XJS drive and call a tow. At your convenience, you should have your system diagnosed by an OBD reader that almost all auto parts stores have on hand and will gladly connect it to your car at no charge to get a fault code. I had someone ask a question this week about a fault code of P0302. So here is a list of the typical symptoms most people experience

  • Check Engine Light that is on solid or flashing
  • The car will not start or is difficult to start
  • Car hesitates during acceleration
  • Engine runs rough or idles rough
  • The car has a lack of power while driving
  • Car dies or stalls while stopped

Here are the most typical causes of a fault code of P0302

  • A defective spark plug in cylinder 2
  • Lack of compression in cylinder 2
  • Damaged or worn-out spark plug or the wires plugged into the coil
  • Defective or clogged fuel injector normally found on a car that sat for many months 
  • Clogged EGR valves or tubes
  • Burned valves
  • Ignition timing that is inaccurate
  • Vacuum leaks
  • Low fuel or low fuel pressure from a bad pressure valve 
  • Leaking head gasket
  • Bad camshaft sensor
  • Bad crankshaft sensor
  • Bad mass airflow sensor
  • Bad oxygen sensor
  • A bad throttle position sensor
  • Bad catalytic converter

There are so many things that can be the culprit of the check engine light coming on and I have had a few in my 95 XJS. One was caused by the hose to the charcoal canister being plugged off with a bolt which also caused the fuel to back up out of the gas cap when full. Hence buying a classic car and not knowing what or why someone did what they did. And another was caused by a bad air pump but not diagnosed until after burning out both catalytic converters. My tip is this. If you have a code of P0302 and the car sat for a long time, start by adding some injector cleaner to the fuel and drive out the old fuel and replace it with fresh fuel and cleaner. This is an inexpensive start that just may solve the problem.

1 comment

  • it’s always a pleasure to read your articles. Cince this is my first XJS
    I need to learn more about that 4l 1995 facelift convertible I purchased not that long ago.
    I’ve been working on cars as a hobby for many years so I’m familiar with working on them

    Jon Tore Jacobsen

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