My 2001 Mercury Sable idles roughly at startup. However, if I give it a little bit of gas (ie: pump the accel. a few times) it smooths out and runs fine. After that, it runs great as long as its not off for more than an hour or two. Once or twice it has thrown a P0301 code (#1 Cyl misfire) I've had it to local shop here and they couldn't find anything wrong. It has new plugs and wires, the coil for #1 cylinder has been replaced, and the computer has been updated. It seemed better for a few days, then back to as before. Someone told me that I might have a leaking fuel injector in my #1 cylinder and that I should check the fuel rail pressure after shutdown to see if it is leaking off rapidly. I haven't done that yet. Any help would be appreciated.

 

One easy thing to check is the condition of the PCV hose. From the drivers side you can barely see it behind the throttle body. Reach back there and feel the hose where it bends to connect to the intake manifold. It may have gotten soft and collapsed/or cracked. With the motor running you can flex it and if it is cracked like mine was you will hear the air leak. The hose is available on Amazon for about $15. It's a pretty easy fix if that's what you find. Let me know.

 

Thanks. That hose elbow failed on me a couple of years ago and I replaced it. I checked it again though and it still seems to be ok. We replaced the fuel filter about a week ago and that seems to have been the fix. I haven't driven the car much since then, but, so far, it seems like it is running fine. I think maybe this was the problem all along but, throughout this ordeal, I believe we also fixed some other things that need a little attention. Time will tell! Thanks again for your suggestion.