i have an 02 f150 screw with 4.6L V8. the other day i changed my oil and airfilter as well as cleaned the engine by hosing it down and spraying in some armorall. the next day when i started it up the check engine light came on and then as i started to drive it the engine was knocking around. the knocking went away but is now back and the check engine light is now blinking. i thought maybe it was wet from cleaning it out and needed to dry out but it still is knocking and not riding smooth. went to advance auto and they hooked it up and this is what it said... need to know how serious this is and how much it will cost to fix this. thanks

1. Code P0303 Cylinder 3 misfire detected.

2. Code P0442 EVAP Emmision control system leak(small)

3. Code P0316 Misfire Dectected 1st 1000 revs

 

You got your COP wet on cylinder 3. Pull it and dry everything out. You may need a new one. Evap can be loose gas cap.

 

Hosing down your engine was the source of your problems. The COPs don't like to get wet. You can try pulling that one and drying it out. You may need to replace it. COP is the coil-on-plug.

I agree the evap code is probably a loose gas cap.

Dry out number 3 (BTW that is pass side 3rd back) COP, disconnect battery for a few minutes and this will clear the codes. If it comes back or is running rough (misfire) then you need a new COP. You may also have additional COP that have not failed form the water *yet* and you could have more problems. If you need new COP(s) the recommendation from most on here is to replace all 8 with new, about $100 on ebay.

 

Yea, if you can't figure out the EVAP right away, don't concern yourself yet. Fix your misfire first. When you re-boot/ firing on all eight and the code comes back, there's a definite problem with that system.

At times these computers can fire of a bogus code/s along with a misfire. Misfire is correct, but what follows isn't always.

Misfire first

 

Code 442 is usually a gas cap leak. Considering the age of the truck, the gas cap will probably need replacing. DO NOT buy just any after market cap. Use a Ford only cap or expect to have this as a reoccurring issue.
If you haven't replaced the COPS, now would be a good time. Usually when one gets flaky, they all start going bad. The best are also the cheapest and can be found on Ebay. The P0316 means you have a random misfire at startup, not necessarily #3 which would lead me to believe you have another COPS about to crater. Otherwise, you would only have the 303 code.

 

Right, I didn't think about that, the 316 could be another. Either that, or #3 is real close to primary failure. Primary would be a solid CEL instead of a blinker.

 

Also, you could have water in the spark plug wells. If your boots on the coils are the least bit cracked, it will short out in the water and cause you all kinds of misfire codes. Easiest thing to do would be to use an air compressor to blow any water out of the wells. Re-set the computer, and try it again. Your issue is with water. That's the only thing you added into the mix. These Modular engines don't like water.