I got two engine codes now. One is something along the lines of "System to Lean" and the other is Cylinder 8 mis fire. I can clearly here it mis firing when I get on it a little. Sometimes it will get up and go fine, others it will spit and sputter and miss real bad for a bit then go right on and do what its suppose to. Guy at work is telling me TPS could be in need of being replaced, since it seems to do just fine part of the time, and it seems to also be related to where my foot is on the pedal when it does it. Sitting in the drive and reving it doesn't seem to make the problem appear. It seems to happen whilst in gear and driving. Any help with this would be great.

Its an 04 Ford F150 SuperCrew Cab FX4 with the 5.4L Triton V8. Has 126 thousand miles on it.

 

OK we are going to assume that you have had the plugs changed but have you changed the COP's for the plugs yet?

I would move the wire for #8 to another plug and see what happens. That will help to key you in on whether or not its the COP's or something else. Also if you have changed the plugs what did you change them to. Did you stay with Motorcraft or switch to another plug such as the Champion. Some people have had issues with the Champion plugs after several thousand miles and the plugs just needed to be replaced to correct the misfire problems.

The other code for the system to lean when was the last time you changed your fuel filter?

 

Well truth be told I do not know if the plugs were changed or not. As much trouble as it is to change them out, I'd hate to pay an have them changed if they were just replaced. On my ranger those codes popped up when my fuel pump was on the way out. I changed the fuel filter on it, and it was a motorcraft that was on it so it was probably an old fuel filter, but that didn't help it. Tonight it was a lot better. The missing was very slight but still there, but again only on hard acceleration... I sprayed the throttle body down good with some carb cleaner, and got a lot of black stuff out of it. It didn't appear to change much. I seafoamed via vacuum line and yes I know that I should change my plugs after doing that but again I don't got 1200 bucks to throw away if one of these things brakes, nor do I have the tools to get to them at the moment.

So I was hoping a simple fix like TPS sensor or something else. Being to lean means not enough fuel, which could also cause a mis fire in the cylinders, if its getting enough fuel all the way up to cylinder 8 and that is the one causing the issue then maybe it is something besides plugs or coils?

When everyone says coils I assume you mean "plug wires" or are these different? Oh and I got some MAF cleaner, and took that out, and sprayed that down real good as well. Didn't change nothing. The truck idles great, and if you just drive it normally its fine. When you stomp it or half away stomp it is when this problem shows up, and it doesn't always happen, and sometimes it worse then other times. It seems to lighten up after its warmed up, it was real bad this morning, and tonight when it got colder it seemed to be hardly noticable. I can't say either way whats related and whats not.

 

The lean code I would stick with the fuel pump that seems like the next place to look at for the problem you are describing.

As for the misfire yes it could be because of not enough fuel but I would guess that the plugs or the COP are about to go. These trucks don't have the old style plug wires and distributor cap like some of us are used to they have coil on plugs or COP boots but they are basically the same thing.

Anyway I would replace the pump and see what that does for you and I would also take the COP off of #8 and move it to another plug and see if the misfire occurs on that plug. If that is the case then the COP's need to be replaced. Also if you read around here and get the tools changing the plugs can be a little bit difficult but its possible to do it yourself. The lisel tool is not too expensive anymore so most of us have one by this point.

Keep us updated as to the progress and good luck.

 

Are all the plugs fairly easy to get to ? Replace the whole fuel pump? Is there nothing else that could cause this?? A guy at work said the Throttle Position Sensor would do that, but I was doubting that, but it is a cheap fix. The fuel pump shows at idle 180 PSI when I checked it on the pcm computer thing that is built into the dash.

 

No not all the plugs are easy to get to. I want to say the #8 plug is the hardest and to make it easier you need to disconnect the air filter. There is a good thread done just recently by a guy who got all the plugs out without breaking any. Now you could follow everything he did and still break one but its not the end of the world. From what I am also seeing is that people who don't put back the motorcraft plugs seem to have more issues sooner with the plugs again. To be honest I am not entirely sure about the fuel pump but that would be the next route I would take if the problems is consistent. I doubt the TPS as well but you never know somethings happen different in ever truck/vehicle you work on so it could be.

 

Would the Catalytic Converter cause this? Being stopped up that is?

 

That I don't know.Someone else may chime in shortly though on the Cat being a potential problem.

 

Yeah like I said I am trying to narrow it down to something else. The plug wire has been changed, still showing that code. It seems like its being robbed of fuel on hard acceleration. It doesn't appear to do it when its sitting in park and you red line, but it does do when driving, and you stomp it. It cuts out and pops for a second, sometimes its worse then others. The other day it was so bad that it did it enough to throw those two codes. I cleared them, and they are gone as of right now.

The fuel filter may be stopped again so I am gonna go get a motorcraft one tomorrow, and put on it, since this one was like a cheapy. I heard injectors on here before to, wonder if that would cause lean codes? I would think an injector would be messing up at idle as well though. What are the symptoms of a bad TPS sensor? I know its a "throttle position sensor". I was also told the IAC could be dirty... but that also don't sound reasonable.

Hopefully someone chimes in here soon.

 

mine did the same and it was a bad plug and it would work unless you stomped it and it could not keep up with the fuel and it was bad(popping and bucking) i did not get the lean issue but that could be a bad reading from the 02 sensor because of what is going on with the motor.

 

You know what could of happened is when the plugs were changed (if they ever were) maybe they didn't change out the #8 plug because it is harder to get to. Maybe the previous owner decided they would push it and then sold the truck so they never had to deal with it.

 

I dk its not throwing codes or acting up near as bad. Doing a lot better, still off and on though, but not as severe as it was. At least tonight that is. All I did was clean the tb off and run it while spraying carb cleaner down it. I have confirmed that even at 3-4 grand in drive is where it does it at, but in park you floor it and it will go to 5 and not miss or pop none at all.

That being said any ideas? To bad you live all the way in VA I'd just about be tempted to drive up their and have you help me change these plugs. The dealer will probably charge me out the *** for it.

 

My buddy that works at a ford dealership says fuel rail or injector. How hard is to remove either of those?

 

i hate to break it to you but thats what mine did also. you could rev the hell out of it with no problems but if i try to run it hard it screwed up and if i did not lift it would throw a code. the fuel rail and injectors have been a problem but that was with leaking and then filling the cat up and clogging them

 

So most likely just need new plugs and plug wires? Very unlikely it is injector or fuel rail? Mine isn't throwing a code at the moment even when I keep on it, it may do it bad, or may not do it at all.. or it may be very slight. So far since I reset the codes, it hasn't thrown them.. It goes ahead and works... So yours did turn out to be plugs.