Misfire on one bank only
 

Hi,
I am driving a `99 Boxster 2.5.
This car has lately developed a misfire only when the car idles at working temperature.When the car is cold there is no misfire and when driving the car the engine runs smoothly. The engine management light remains on .
The fault codes indicate that the three cylinders on bank 1 all misfire I have replaced the lambda sensor on bank 1 but the problem persists

Any suggestions what causes the rough idling and how to address the problem?

Check spark plugs and inspect ignition coils. Any wear or small hairline cracks on ignition coil can cause misfire. Also do you know the last time the fuel filter was changed?

On a side note. I had similar fault codes with my wife toyota sienna. Error wouldn't clear until I changed all of the oxygen sensors. I put 76 gas in my wife's van cause I was no where near my usual gas stations, and the engine light came back on. When the van was due for fill up again I put Chevron and engine light almost immediately turned off. I only use Chevron or Shell in any of family vehicles.

fault at idle is typically vacuum leak. engine doesn't draw much air at idle so a vacuum leak can throw things off. when driving the engine draws a lot more air so a small vacuum leak does not affect things.

did you find out what was going on with this misfire as i am having a similar problem