car cranks but won't start getting good spark

What is said on the machine was it was a random misfire

can the ratio be changed to improve fuel mileage

back fires also sometimes

It's as if door actuator dosn't turn off when lowered.

The lights dimmed and then got brighter before shutting off. I have replaced the altenator and the battery I even replaced the wires.

My f150 leaks oil alot. I can not tell where it is coming from but assume there is a leak in the oil pan gasket

I have a 2006 ford freestar (4.2). Emissions light came on and I thought it was fuel related so I changed the fuel filter (150,000 miles and it was the original part :-O ) Didn't fix the problem. I figured if it was the O2 censor then my check engine light would have come on and if it was my fuel pump my car wouldnt even start. The free diagnostics wont read a code since its not the check engine light. My next guess is plugs and wires? I can't really afford to pay to have the code read or to keep changing stuff until I find the problem. any suggestions?

the abs pump runs when the car is turned off

I took it and had the code read and it stated that the engine was running lean. Is there something I can do to fix this with out taking it to the garage for repair?

Once it warms up and a lot of stop and go, it jerks like it's tearing apart when I go again. I have to gauge traffic lights so that I don't have to stop.

I had an o2 sensor a exhaust part repaired and the check engine light still comes back on
. i need to have a emission test done on it and i can't while the check engine light is on . can you please help me out.

also was wondering and have been told that valve guides are leaking and causing oil to blow by and come out exaust after sitting at red lights for a few much extra should it cost if also doing valve cover gasket replace...

I have tried everthing I know to do I have pulled with over 200 lbs. of pressure and the boot will not release from the tranny please tell me what I'm doing wrong

No trouble lites appeared before problem, none are on now. The transmission still will not shift from low to drive
This is a 2004 C230 Kompressor