Check engine light is on?

Miss fire code P0300, and sometimes P0306. Going to swap out number 6# injector later today, to see if it's just that.

When I said I replaced the whole EDIS system, I also replaced the crank sensor after it tested bad. Ring is good cond still. The 5.0l has really no vaccum lines, all ready checked them. Wouldn't the egr system throw a CEL regarding the evap?

The crank is the cam sensor on this one I believe, compression tested the number 6 cylinder last nite and found nothing out of the ordinary. Above 150psi. Might try a leak down today, looking for maybe a possible bad valve. Since they seem to always had bad valves since forever.

Compression tested good, leak down a bit low. Running compression tested good at just a bit more then the 80% for perfect. Higher means exhaust valves. Lower means intake. Nice test for FORDS! Did a hard memory restart over the weekend. CEL is now off after 5 miles so far and all sensor at reading at present time.

I would like to know what wold be causing the o/d light to be turing itself on by itself while driving. Does not happen all the time. Also, the check engine light will come on, was told could be due to air getting in by the cap, have replaced the cap, bt still comes on at times but will turn off when cap is taken off and put back on. Wait a few days light goes ot, but comes back on after a few days.

My check engine light came on about 3 weeks ago. I took it to advance auto and they put that computer thing on it and the guy told me that older suv's like this one ** the light comes on sometimes when the weather changes or is real cold. And it was cold. Unusually cold. Well he reset it. Well it came on again today so I took it back to make sure it was ok. Another guy put the computer on it and said he didn't know what that code was so he asked his boss. The boss said it was probably the thermostat. And he said my antifreeze was low. I told him it was not cause I had gotten it service a couple of weeks ago. Well he put it in anyways and it didn't take much of any.. Now that I told u all this. Do I need to put a thermostat in or is it the changing (very cold) tempertures we have been having around here. Or is it the 02 senser. Could u please give me some direction. My truck is not over heating at all and i'm confused. And yes i'm female and I hate thinking people are selling me stuff I dont need. And I dont want my truck to break down.
Thank you
pat

The man at the auto advance store could not remember the code and he said he erased it but he said it meant or said "close fuel control" - temperture koolant low. He put some in but it was such a small amount that would even go in.
Thanks
pat

Does this mean I need a thermostat. Or is it a sensor.

I'm sorry I realize you are telling me it's something else. But since I don't know much about this I guess I better take it somewhere.

Thank you so much

Anyways. You are talking about a sensor, right. Not the thermostat that I bought right.

I'll leave you alone on this one. I just want to know if I should take that thermostat back and find some one to fix the sensor. Also will my truck mess up if it takes me a little while before I can get the sensor fixed.

Thank u so much for putting up with me.

I'm done.

I have a 1999 Ford Explorer Sport with the 4.0 efi engine. Yesterday on the way home, the car studdered and stammered when I hit 50 mph but after I cleared fifty, the car sort of stopped the vibrating and the stammering. This morning when I started the car, it was running really hard and on my way to work, the check engine light came on. I plan on stopping at the autozone and let them hook up the little meter to get some codes. I would look up the codes and hopefully I would get a better idea of what is going on. Please advise. The car has never given me any trouble before.