Normal MAP sensor pressure at idle?

[keithatcpt]

What is normal manifold pressure at idle?

My 2000 S40 with 184k (160k on the engine) has been misbehaving recently. I'm getting a P0304 Code - cylinder 4 misfire along with the blinking check engine light. This is only happening at low rpms; at full throttle, the misfire goes away and the engine (mostly) smooths out. I'm thinking that I've got a vacuum leak because the MAP sensor is showing a little over 15 inches of mercury at idle, and I would think that the manifold pressure would be lower at idle. I've replace the spark plugs with plugs from the dealer (the plugs were shot). I've also swapped coils and wires with spares I had from the original engine in this car (no improvement).

I know I'm on borrowed time with the coils and wires, I'm probably going to end up replacing those as well. I saw the manifold pressure on my ODB reader, just seemed like another thing that could be wrong.

Thanks,
Keith

[jimmy57]

15 inches idling in gear is completely normal.