'03 MCS. Seems to be misfiring and when cruising I can mash the pedal to the floor in 5th or 6th gear and I get absolutely no pickup. Is it starving for gas/air? Could it be an O2 sensor issue? The SES light is on, and the manual says that is an emissions issue. A friend pulled codes a couple weeks ago and it showed a Cylinder 2 misfire. The plugs are new and I just put new wires on.

One thing I noticed while messing around with it was that when I take the Oil filler cap off, there is a lot of air movement, pulsating, coming up out of the valve cover. Could that be a valve problem or rings problem?

Any ideas??? We have about 69K on the little bugger and it seems to be coming up with new and different problems all the time now.

 

anyone?

 

did you just fill up your gas tank? maybe you just got some bad gas.

 

new plug or wire could be bad

 

If you were closer to houston I could pull the codes and do some logging to see what is going on....damn!

I saw you posted on metroplex and I tried to help you there (Ballzob).

 

If the problem was more general I might say it was the bypass valve. They can act-up and make the car sluggish in certain conditions.....I've heard.
Might have that checked out specifically.

 

Pull the spark plugs and examine each one. With all of the electronic diagnostic stuff on the cars nowadays, people seem to forget that you can tell an awful lot about the general health of the engine just by the condition of the plugs.
You're in a fortunate position in you have fresh plugs and wires. The plugs should be dry and light tan/grey in color. Compare the plugs to each other. Are the the same color? Did the mis-firing happen all at once, or was there a general decline in perfomance?
While O2 sensors can cause mis-firing and rough idling, they don't usually fail suddenly.