I have a 2005 f150 with 96,000 miles. Long story short, last August I was headed to the mountains going up a steep long hill and the engine light come on. once i was over the pass the light went off. During my 4 wheelin' trip it never came back on until I was headed home and going over another pass and then it stayed on for a couple of days. I had it checked and it was a cylinder 5 misfire. I did some research and found that replacing the coil cover might fix the problem and if not the spark plugs would need to be changed. I changed the coil cover, problems solved... until I headed to the mountains. light came on and then eventually went off later that day. I didnt think much of it. then a few months later i was headed to the mountains again and the light came on in the same place on the steep incline hill. I. took it back to the shop, same reading. I decided it was time to replace the spark plugs anyways so I would invest. $500 later I have new plugs and everything is good however, I had no plans to go to the mountains in the near future. Now, a few months later I headed to the mountains and crossed my fingers it would not come on but it did. ugh. iv done the research again and it seemed like the coil cover and spark plugs are usually the cause of the problem...however I have changed mine. anybody have any other ideas or suggestions? the light is now off again. I don't understand what is triggering the problem and what is really happening and if it is safe to keep taking to the mountains with this happening. i did notice that everything was fine at 60MPH but once i hit the hill and steeped on the gas to go 65 and hit 4-5RMP that is when the check engine light came on...thanks

 

Is your fuel filter begining to clog up?

 

Hey I have been having the exact same issues whenever i hit a big hill and step on it to pass someone the rpms go up and then the light comes on and its almost like all the power just goes away but the rpms stay high. I replaced my spark plugs went from 87 octane gas to 89 and also using a fuel additive and it seems to be running better now and i have not had the problems since ive done all this. I would suggest something but i am no mechanic at all, but i have seen many people say check the air to fuel ratio and check to make sure that your truck is getting the right amount of air.

 

Im not sure, i will have to have it checked. I know the dealership said it was time to get it replaced as a general maintence...but they also had a hudge list of other bull**** stuff SO I will go ahead and change that and see if it cures the problem.thanks

 

It's good to change the fuel filter as regular maintenance, but I doubt it is what is causing a single cylinder to misfire at high RPMs. If you addressed the spark already with new plugs and new coil, fuel is the next step, but something more cylinder-specific would be in order. A seafoam or other fuel injector cleaning product would be a good place to start for the entire fuel system, that may also help out a problem injector on cylinder 5. If that doesn't solve it, it could be a bad injector having trouble at high rpm.

Another possibility is bad compression on the cylinder that is showing itself at high rpm, which could be due to a number of factors, and one that you always hope is not the case. That is probably not your issue, as I suspect you would have it more often than climbing hills in the mountains.

 

This might be a long shot, but check this thread: #5 coil wiring issue

 

I forgot about that...definitely a possibility though you would expect him to have the problem more frequently if that were it. Since it's the first plug on the driver's side, it's just a matter of popping the hood to take a quick look at the wiring.

 

Ill try better gas and an additive and see if it works...thanks!

 

good information all, I will look into all of the possibilities and start on the least expensive side and hopefully it fixes easy!

 

Have or do you change your fuel filter? I have the handbook that says how and it seems pretty simple. However, I have hear also there is a button on my year of ford that I can just "hit" and it will shut off the gas then I can change it rather than worrying about the pressure and all that jazz...any suggestions or ideas?

as far as the sea foam, I am not quit sure what you mean. I know when I had the plugs changed they let my truck soak with seafoam for a good day before removing them so the plugs would come out easier...

 

Yes, I changed my fuel filter last week. I just let the truck sit for a few hours and the pressure went down enough that it didn't spray when I disconnected the lines. I know nothing about a button to shut off the gas, I've only had my truck for a few weeks, but some people recommend pulling the fuel pump fuse and cranking the engine, which should relieve the pressure. On my cadillac I have a schrader valve on the fuel rail so i can just cover it with a rag and depress the pin and it relieves all the pressure.

Changing the filter is very easy to do, you just need a fuel line disconnect tool for the side closest to the front of the truck, which you can get at any auto store. Cheap plastic ones work just fine, no need to spend a lot there. The rear line just has a clip that you undo, push out and separate the connection.

Seafoam can be used in three ways, (1) poured into the crankcase to mix with oil and clean that part of the motor (2) poured into the gas tank to mix with gas and clean the fuel system and injectors (3) poured into a vacuum hose to be pulled into the intake and run through the cylinders.

When they changed your plugs they probably poured it in a vacuum hose to clean out the cylinders including the plug tips. I am recommending you run it through the gas tank so it travels through your fuel lines, rails, and injectors.

 

Pull the #5 plug, pull any other plug. Compare them. Do a compression test on #5. The info from these two test is vital for trouble shooting.

 

well, good news for now. I went ahead and changed the fuel filter on the truck a few days ago. Some people suggested this could be the problem for the misfire and it needed to be done anyway. It took a bit of struggling but I got it done!

I went to the mountains yesterday for a wheelin' trip with a group and crossed my fingers as I went up the hill near lookout mountain. I talked with some other truck owners and they suggested switching to 2nd gear or out of OD when hitting the hill to see if this stopped the engine light from coming on. As I approached the hill I turned the OD off and the truck kept the speed of 65MPH and didnt seem to be struggling. I was a bit hesitant to really step on it and give it the power to 75MPH as I didnt want to trigger the problem in case it really wasnt solved. On my way home I decided to be a bit more brave and I turned the OD off as coming up flyod hill but turned it off about 1/2 the way up and pushed the gas more and it seemed to do just fine. I could have pushed it a bit more but it help 70MPH nice and easy and the pedal was not on the floor. as of now its fixed but I will push it harder next time to make sure it really is fixed completely before I start wheeling a lot this summer!