Hey guys, haven't been on here since I got my other truck, but now I've got a problem with my F150. It's a 99 and has the 5.4. I hadn't driven it in several months, and was driving down the highway one day and it started to run really bad. Check code says cyl 7 and 8 misfire. I change the plugs and COPs on those two still runs like crap and gives these codes. Take it to the local mechanic he says maybe rod or piston. So, do I tear it down (don't really have the time to do, but could make it work), replace the motor with a 302 or 351 which I can find pretty cheaply, or just part the truck out?

 

Sounds weird. Never heard of a rod or piston causing a misfire. Is it knocking? Just misfiring? How many miles?
clean the injectors. Put some Gumout for high mileage engines in it and try that first.
I'd check the compression if there is a possibility the mechanic is right.

 

It's always had a tick ever since the first day I bought it. 125000 miles. It has very little power, like taking off feels like I could go faster on a peddle bike. But it idles like it's got a huge cam in it, and the tick is now louder

 

Change the fuel filter, air filter, and put some Gumout for high mileage engines in it.

When I bought my truck, it was low on power. The air filter was the dirtiest air filter I've ever seen. I completely serviced the truck including some Gumout and it ran like it should.

Check the compression at least in the affected cylinders.

 

I would check to make sure all of your plugs are tight and torqued properly 28ft/lbs
If it sat for a while, I would absolutely run some injector cleaner through it cause I'm sure they are gummed up, Techron would be a good choice. Replace the plugs with OEM if they have too many miles on them. Same with the cop's. I wouldnt trust that is has a rod or piston problem. If anything your timing chain may be making a little noise. For all you know it may also be an exhaust leak with a misfire.


I had a single cylinder misfire and my truck ran like crap and was under powered. If you have 2 cylinders acting up, I would imagine it would have no power.

 

I replaced the plugs with Motorcraft and torqued them to the proper spec. When I get home after finals I'll try some techron through it, but I don't know if it'll help it. Another code was something about EGR circuit malfunction or something like that. I'm just trying to get an idea of anything that might help it until I can dig into it after finals when I can really dig into it.

 

Any time you post codes, please post exact numerical codes. Thank you.

 

You probably have a big vacuum leak. That EGR code was critical information! Get that code and POST it. We need to know what going on with you poor neglected truck to be able to help you. My guess is your pcv elbow is rotted out and its causing the miss fire and the EGR code.

 

[IMG][/IMG]

The oxygen sensors I know have been bad for a little bit of time before that, so that's not tied into this new issue. And this truck has been sitting since last October or November, so it's been a while, and I'm assuming it didn't get started but maybe once or twice since that time.

 

Its no wonder your engine runs poorly! I would start with the EVAP system. Check all the vacuum lines and make sure the vacuum canister isnt compromised. Could be a bad gas cap.. The o2 codes generally point to them having a short unplugged or they are bad its unusual for them to fail at the same time. The DPFE codes are sometime from a disconnected vacuum line a bad EGR or a bad DPFE. I suspect Vacuum lines.. The missfire codes are probably a result of all the other stuff.. Good luck!

 

Had some of the same issues in my 98 Expedition then a spark plug shot out of the head :-/

 

I'll try and look through the vacuum stuff when I get home. And I really hope mine doesn't spit a plug...that would not make for a good day

 

You say you properly torqued the plugs, but specifically how much? You need to ignore published specs and torque to 28 ft lbs to keep them from spitting out.

 

28 ft lbs because I had done some researching before changing them because I knew they had an issue with spitting the plugs.