Any one know the cylinder compression for the 3.0? I have an 2003 ranger and Im chasing a misfire on one cylinder.
There is a TSB about valve seats coming loose on the 2002-2006 3.0ls
Cause intermittent misfires
Engine compression has so many variables in the testing methods that to give a specific range is next to impossible.
All spark plugs need to be removed
Larger vacuum line should be removed or throttle needs to be propped open to let air in to be compressed.
Then you have crankshaft speed, which is the point of removing all the spark plugs.
If battery is low then crankshaft speed will be less, new battery faster crankshaft speed.
Metal rings against metal cylinder walls and metal valves against metal valve seats don't provide a long term seal, they leak and should because of the metal to metal "seal".
So the faster the piston comes up the less time there is for air to leak out so the higher compression number you will see.
Some like a warm engine compression test because heated metal expands so a better "seal" will often be seen.
For what a compression test tells you I don't think that is needed, but to each his own.
With above parameters used, I would expect a 9.1:1 to 9.3:1 engine to show approx. 175psi with a 15% deviation at most between cylinders.
A compression test is not for 1 cylinder, info is useless without a baseline, so all cylinders need to be tested and then compared.