I have a 2002 Ford f150 4.2 liter that has about 167k miles on it. It runs great and I have kept up the maintenance on it. However recently it has started to run the 0302 error code. I discovered there is something wrong with cylinder 2 , and the service engine soon light stays on. I changed out the spark plugs (Ford Motorcraft) and also the isolator bolts on the intake to take care of the P0171 and P0174 codes that read. The truck runs fine but I noticed that the gas mileage has suffered. Any thoughts?

 

Are all of their trouble codes gone. It usually takes a good while for the lean exhaust codes to come back if the fault is still present so it may take some driving. Also a lot of times after a lean or rich condition has occurred you need to change the oil to restore fuel trims I doubt this is the case but it would cause similar driveability symptoms make sure the oil does not smell like gas. In the end it will take some adjustment time after a repair like this is made how are you figuring fuel miles to the gallon.

 

I am figuring it out by taking the amount of miles driven on that tank and dividing it by the amount of gallons. If I change the oil though and that doesn't change the situation then what else could it be? Just to let you know I also disconnected the negative cable on the battery for 30 seconds to reset the computer. That unfortunately didn't help.

 

You should not have to change the oil unless it had a fair amount off gas in it. Did you actually see cylinder 2 misfire. Sorry if I miss understood but is the cell and misfire code still there. A one cylinder issue affects the whole bank so if the misfire is present then you would get fuel milage issues like you have.

 

Yes I had the codes run at Autozone and it came back as the 0302 code I mentioned. The code was traced to an issue at the cylinder 2.

 

For a start you can check for spark and injection pulse. Do you have a inline spark tester and a test light a volt meter could help if you don't have a light. What you want to do is find out what's missing fuel spark or compression. Once you know what's missing then diagnose the issue from there. Note that misfire data is not always the most acurate so verify the misfire on cylinder two before anything else.

 

Swap cyl 2's spark plug with cyl 1.
Swap cyl 2's plug wire with cyl 3.
Swap cyl 2's injector with cyl 4.
Then see if the misfire moves.

 

IF you have a 302 code, you have a 90% chance that the COP (coil) on that cylinder is the problem. Replace or switch 1 and 2 and see the problem move to #1 cyl.

 

Steve(ill),

Thanks for the advice man! I swapped the spark plugs in cylinder 2 and 1 and so far so good after 50 miles driving. See if that fixes the problem!

 

?? If you had a fouled plug or loose COP on top, that could have been the problem. Normally swapping the plugs wont do much good. Missfire is normally related to the COP on top.. If you don't get a code, then I would assume the COP wire/ boot was loose - dirty- or not seated correctly............ Plugs looked OK ?

 

yes the plugs looked good on cylinder 1 and 2. gap seemed ok. Truck is running good with about 100 miles on since changing. No service engine light back on. I did the calculations and the truck got about 17 mpg which concerned me. I dumped in some fuel injector cleaner to get that back up to the 20 mpg which I should get on a 4.2 liter. The wife drives the truck to work about 30 miles one way so I want her to be reassured that it is running good.

 

Well unfortunately some bad news! Service engine soon is back on and cylinder 2 is still misfiring. Now I have a P0316 code which apparantly is a crank sensor that may be defective, connector is loose, or trigger wheel is damaged. I dumped in some fuel injector cleaner earlier when I filled up and also changed the #! and #2 spark plugs as suggested. I also moved the spark plug wires from 1 to 2 and then back to original places but that didn't help. Any suggestions?

 

Did you move the #2 fuel injector?


If you did with no change, its time to do a compression check.

 

No I still need to pull the #2 fuel injector.

 

Update:

Have not gotten a chance to work on the truck much , but I did do a compression test today on the #2 cylinder and came out to be 190 PSI. That is certainly in the good range. I did the #1 compression test and came out to be the same 190 PSI. So that is not the problem thank god. Have it narrowed down to either the fuel injector or coil as mentioned before in prior posts.