My motor is shaking in idle and has low performance. I changed the plugs today as they were due but it didn't make any difference. The engine malfunction light is on and a message is displayed "reduced engine performance". Any suggestions or will I need a diagnostics performed ?

 

Yes, is the answer. The car fault detection system has detected a potentially damaging fault, so has put the engine into "restricted performance" mode. It posts a code into memory to give mechanics a clue as to what could be defective. Basically the system compares values from various inputs from engine sensors and compares to what they should be in the particular circumstances.

 

Hi,
You can use a diagnostic OBDII. It's important to know the reason why the the engine is into restricted performance.
It can be important not to run the engine.

 

Thanks, I bought the OBDII and I get a message that cylinder 5 is misfiring. Any suggestions from here ?

 

Bad coil? Did you gap the plugs correctly? Did you use iridium plugs?

 

I now know it's a bad coil. I switched coil #5 with #1 and now the display is saying #1 is misfiring. Yes I used pre-gapped iridium plugs. Now I have to do some coil shopping
Thanks everyone

 

Glad that was an easy one!

 

I'm glad I bought the OBD2 it made it much easier to trouble shoot and I can use it on my Crown Vic as well. To top it off the OBD2 was on sale for a $100 off.

 

The first thing is not to start the engine befiore replacing the coils. The gazoline can disolve in oil that's not good for your engine.
How many miles has your car ?

 

The car has 80,000 miles on it now. The new coil is now installed and she is purring like she used to. I shopped around for a new coil and Jaguar had everyone beat on the price, it looks a little different then the old ones so I'm assuming it's an improvement just like the blower resistor pack.