I have a 1997 F-150 with the 5.4 Its really starting to **** me off....At idel it runs real ruff like its missing but as soon as you give it some gas it runs like a champ! So today I replaced the TPS, fuel filter,spark plugs and air filter and still does the same thing. If anyone has any ideas PLEASE let me know.


Thanks

 

when u say it mis-fires does it trip the CEL(Check engine light)?
Your friendly, digitally local, ASE cerified mechanic,
Josh

 

okay a couple things:

After you replaced the TPS sensor did you recalibrate it?
It should be reading about 9.95 volts.

Next get your timming light out and see where it's sitting.
Mine likes it at 10 btc.

 

a timing light is useless with these engines. you cannot set the timing and/or adjust it.

timing is affected by many things.

IAC, MAF, Air Temp sensor, Coolant temp sensor, Crank angle sensor, O2 sensors, vac leaks, etc.

If no code are thrown (CEL on) or the CEL doesn't flash than it is mostlikely a bad IAC (Yes a new one can be bad) dirty/faulty MAF (Most likely suspect here)

you will also want to make sure your coolant is full so that the coolant temp sensor can get an accurate reading. if the temp sensor thinks the engine is still cold the pcm will keep the at rest idle in a cold engine setting which will be very rough when the engine is warm.

also your year truck is famous for the big elbow hose right up against the firewall for failing. just run your hand over it while the truck is running and you will feel the crack or vac leak in it.

good luck-

 

So today......I was checking all the VAC lines and sure enough!! the VAC line running from the pass. side pcv valve to the back of the intake had a crack in it. I had the truck running and I was feeling around then I come across a HUGE leak almost sucked my finger right in, So at this point my trucks sittin there ideling like it has a cam....I pluge the hole with my finger and it smooths right out.



And another thing...My check engine light has been on for about 5 months now...I thought it was the vac leak causing it, after I fixed the leak I disconnected the battery for about 20 min to clear the code. The light was off for about 10 miles then it popped right back on. Any ideas on this one?

Thanks guys for all the help

 

go to autozone and get the codes read for free. then post them here..