I have a 1998 f150 4+4 super cab 4.6L which I purchased new in 1997, it has 45000 kms (27000 miles), stored winters. Idles great no hesitation around town or cruising, but when I kick it into passing gear it hesitates bad. Check engine light did come on but I reset it before I could get it checked. Its still in storage, but does anyone have any idea, or will I have to get "check engine" light again? Thanks

 

when was the last fuel filter change? has the engine been wet before? with the mileage i'm guessing its never been tuned up? maybe dry rotted wires. it may also be dirty injectors from old gas sitting in the lines over the winter.

edit: welcome to the site

 

Plugs look like new,no carbon buildup good gap and not burned ,I changed the wires(Ford original) and gas filter, I start the truck about every 3 to 4 days and keep fresh gas in the tank, keep fuel injector cleaner in it in the summer, and gas line antifreeze in the winter. do you think the plugs should be changed anyway? The truck has never been wet.Thanks for the welcome.

 

when did it start to misfire? plugs may need to be changed with the age. would you happen to have a fuel pressure gauge? i'd check the fuel pressure too. was there any dielectric grease left on the plug(s) that you checked?
the reason i asked if the engine got wet is because water gets down into the spark plug bores and into the coil packs and causes alot of misfires. you didnt have any heater core hose leaks or anything like that?

edit: you may also want to look at the DPFE sensor and hoses. if the hoses are cracked and/or if the DPFE is broken then that could also cause your problems.

 

It started the misfire 2 summers ago. No I don't have a pressure gauge. What should it be? Not sure what the dielectric is.Is that the silicone in the boot? No other problems with the truck at all.Don't know a lot of mechanical. What is the DPFE and where is it located ? Thanks.

 

dielectric grease is the silicone that is put in the boots.

i'm pretty sure this is the style DPFE you have. fuel pressure should be no less than 35psi at idle.

 

Yes that looks like the same one. Can it be cleaned? I'm going to change the plugs as you suggested anyway. What# should I use,same as original? Reading the forums they look like a problem to change close to the firewall,do I need to be concerned about the breaking thing? I have changed plugs before in a crown vic 4.6L. shouldn't be much different.Thanks.

 

the DPFE sensor cant be cleaned. theres probably nothing wrong with it but age may have gotten to the hoses and dry rotted them, so just look at them just to make sure.
as long as you use motorcraft, denso, or ngk spark plugs you will be good.
make sure you put dielectric grease inside the wire boots. dont fill them up, just pretty much put it inside the end of the boot.
the breaking problem is only on the 5.4 3v engines.
i dont think theres anything in the way for your 4.6 so it shouldnt be too bad.
good luck

 

Missing just in passing gear hints a fuel problem/low pump pressure/bad regulator.

Procedure would be to eliminate a possible fuel problem.

Clean the MAF sensor.

Inspect PCV system (All of it)

Look for damaged hoses.

Inspect wire harness/passenger side/below the MEGA Fuse block/top of AC accumulator. If the harness is resting on top of the accumulator, - The M field creates havoc on these ignition systems. Can also bare wires and short.
Harness should be pulled away (about an 1") If resting on top, zip tie back and away/ check for obvious damage/test drive - Harness sags over time, can and has caused ignition problems..

A Haynes or Chilton manual can be had for that model at almost all 3rd party suppliers. These explain the procedure, you'll want one for this. I have Ford service DVD's , Online accounts and both Haynes and Chiltons manuals. Still use those manuals myself frequently - definitely worth the $20 or so to get one.



Could be a coil pack/plugs/wire issue. Run scan anyway, - intermittent misfire codes can and have stored in the KAM (Keep Alive Memory) regardless. You have about a 50/50 chance retrieving one when scanned. No CEL has to be present for misfire monitor detection. - Auto Zone scans free. Head over there , grab a manual and have them scan it and write the codes down.

 

Thanks guys really appreciate the info. Thanks again.

 

Hello, just an update on my problem. I changed the plugs, I installed the NGK platinum, only one was a problem to get out. All the original looked good. The plugs on one side were AWSF32PG the others were AWSF32P. slight difference in the tip.Is this going to matter? Checked out all hoses on vacuum everything looks good no dry rot, they are just like new. Cleaned the MAF sensor with contact cleaner, had the codes checked, nothing stored. Hoses on DPFE look good. Won't know till summer when I take it out on the highway if the plugs did the trick. If not, whats my next step, Coil packs? Thanks.