02 f150 blew out a spark plug #7, no big deal replaced it using a dorman kit and a new coil pack. Started it up and it has a slight miss but not all the time im gonna say about every other time the cylinder fires. You can hear the miss if u put your ear on the cold air intake filter (found out by accident). It makes the truck shake slightly and if u put it in gear with your foot on brake it gets worse? If you give it some gas saying over 1500 rpm it smothers out and runs like a top from there on up. Its just idling and very slight throttle. I thought maybe it was the plug so i pulled it out and it looked white so im guessing its burning hot, replaced the coil on plug and no difference. I have heard that when it blows a plug it might damage the injector but it look fine , also head that sometimes it damages the computer? Anybody know of anything to check of look into? Im at a loss and no garages around here have a computer capable of seeing whats wrong!

 

We need to clear up some items first.
The injector is only near the coil on the outside.
Inside, the two are spaced a long way apart from the cylinder.
If you hear a miss in the intake, a cylinder's intake valve is not sealing.
The noise you hear is 'pump back' into the intake through an intake valve leak.
Check the compression to find the cylinder causing the leak.
A vacuum gauge might even point this out at idle by a momentary needle dip when that cylinder leaks back.
Certainly the motor will seem to smooth out at higher rpm because the leak back becomes a small percentage of the total combustion pressure after firing at higher RPM..
.
An example of this is in the simple Briggs and Stratton single cylinder power equipment motor with rope start. The camshaft is designed to hold the intake valve open small amount to lower compression pressure or you could not start the motor by rope without risking a broken wrist, fingers, and or a broken rope. It takes a specific crank position before one would try to start this motor without it. After it starts, the small leakage is of no consequence at it's normal working RPM so you would never know there is a built in leakage.
Good luck.

 

^^^^^^^^^^^^^^^^ What he said... ^^^^^^^^^^^^^

Also, your average compression tester won't work on the Ford modular.

 

Sounds like a place to start i have a vacuum gauge so i will test it and get back with you might be a couple days though.
So you dont think if is an injector or the ECU?

 

spraying carb cleaner around the intake and injectors can find a leak fast because the engine starts to run smooth when the spray seals the leaks. Does nothing for checking inside parts, injectors,valves etc.. Vac gauge and a good compression test will tell you everything you need to know. do the spray first, easy and cheap.

 

I have tried this method before and it has worked. I definitely gonna try the vacuum method on Friday.

 

Ok I got around to testing the truck here is what I found. I tried the carb cleaner around everywhere and no pick up on idle so I'm assuming no vacuum leaks. Also used a vacuum gauge and on idle it read 15in and if it is in drive with foot on brake it would drop to 13in and start to raise back up to 15in after about 30 seconds. Where should I look into next I'm totally at a loss?

 

Vac sounds OK. The only think I can think of is may be some weak coils. TB still dirty? MAF dirty? don't know?????

 

MAF is clean as well as the TB. Oiled cold air filter too much so i had to clean all those. It does fell like a bad coil pack come to think of it. No may to tell if its bad until it throws a code. Right?

 

Go back and read what Bluegrass said.