2007 Chrysler PT Cruiser rough running at idle speed

When you rev your motor while in "P", the computer will prevent you from going past 4,000 r.P.M.S. (This is designed to protect your engine)

As for your engine running rough at idle, your computer turns on the check engine light when it wants to tell you something.

You need to have your computer scanned. AutoZone and other major parts stores will do this for free, as well as provide you with the definitions to the codes.

If you'd like to do the work on your car your self, write back once you get the codes and I'll walk you through it.

I really need to know what the code was. P-?

There's more than one kind of misfire. There's an ignition misfire and a lean (fuel) misfire.

The ignition misfire could be caused by a fouled spark plug, bad plug wire or failing coil. And before you replace the faulty component, you have to find out why it's misfiring and whether or not that has to be cured first. Otherwise your new component will begin misfiring as well.

The fuel system could cause a misfire with a sticking fuel injector, bad wire/connector or failing injector driver inside the computer.

This also needs to be remedied or the new component may misfire.

Write back with the code and I'll look it up on AllData. In the mean time, don't replace the plug because we're not sure that's the problem yet. And money is too hard to come buy.

Sorry it took me so long to get back with you. I was out of town for a couple days.

As for your Cylinder #2 misfire:

Turn your engine on and pull the plug wire for that cylinder. If the engine drops noticably in r.P.M.S, then you know that cylinder was firing. If it doesn't, then it's dead.

Next, run the engine for 5-minutes, and while rinning, use a stethoscope to listen to the injector for that cylinder. (To know what a working injector sounds like, hook the stethoscope to a cylinder that you know is firing. You'll hear a clicking sound) If you hear this clicking, then you know that injector is firing. If you don't, then it isn't.

Next, shut down the motor then pull the plug for that cylinder. Check it for oil (Black/wet/filmy), and/or fuel (shiny/smells like gas).

This is to see if the plug is being fouled. Then install an in-line spark checker and reinstall the plug. Remove the fuel pump relay and crank the engine while observing the plug.

If you see a crisp blue spark, then the coil/wire/plug is fine. If you don't, the you need to check the wire (resistance) and the coil (faulty unit).

What you are basically doing is isolating the system that's causing the misfire. And you want to make sure this condition doesn't repeat itself.

If there's a lot of oil on the plug, then one/more of your valve guides/piston rings is excessively worn and needs to be replaced.

If your injector is dirty and sticking, then you need to have your entire fuel system cleaned. Otherwise your new injector will get plugged also, including some of your other injectors.

There are several other things that could cause a misfire, but since yours is occuring in just the one cylinder, those are less likely to be your problem.

So stick with your injector/wire/harness and plug/wire/coil for that cylinder. Test each component until you find your guilty party.