I have a 1999 F-150 with the 4.2 V6..It has 139000 miles, gets great gas mileage but the engine has a miss. it isn't there all the time, it comes and goes, sometimes severe..sometimes not bad...I have replaced alot of things I thought would be the problem..started with fuel filter and spark plugs...no luck...then IAC....no luck....ignition core...no luck...I'm at a loss, there are no fault codes on the computer, been to the dealership, wasted alot of money...does anyone think it may be the key (transponder) causing these intermittent missing episodes? your help is greatly appreciated!

 

Was there any misfires showing on the misfire monitor in mode6 of the diagnostic scan. Also, have you read your fuel pressure?

 

I had the whole system scanned, no codes for misfire...and im not sure of the fuel pressure...how is that checked?...on the scan as well? they said everything looked great on diagnostics...

 

It sounds like you are having the same problem I am starting to have. I have also noticed a longer cranking time when starting the engine. I suspect it is a fuel issue because if I turn the key a wait a few seconds, she turns right over. If I jump in and turn the engine over imediately, thats when it takes a few extra seconds to start. While driving the truck, she seems to hestate once in a while. It is hard to explain and I would dread the thought of trying to explain it to a mechanic. I can just picture the "deer in the headlights" look I will get.

 

sorry to hear you are having the same problem. I still have not come to a conclusion yet. Although I have noticed if i do not use overdrive (i.e. 5th gear) on the highway it does alot better cruising..but it still has the miss at low speeds and when accelerating at highway speeds..im wondering if it is a pump problem? or perhaps a timing issue?

 

I was thinking of a fuel pump problem also because of the longer cranking time when starting the engine. Both seemed to have started at the same time. I put a can of Seafoam through the tank along with a fillup of premium gas to see if it made any difference. It hasn't so far. I just need some time to investigate further.

 

I did the exact same thing, added sea-foam...didn't do the trick...and did super unleaded...no change...i guess we may need to think about pump issues...but im not sure how to check that without pulling the tank?..alot of work if it happens to be a ghost hunt again....let me know what happens with yours..mrcessna_js@hotmail.com

 

On another thread, a guy said this engine was just basically a bored out Ford 3.8 liter engine. I have a Ford Windstar with a 3.8. They both use the same oil filter among other things. The Windstars are notorious for the EGR ports under the intake manifold clogging up and causing fuel air mixture problems. I fought with that damn thing for aver a year until I found a good forum like this but just for Windstars. A guy posted pictures of how to tackle the problem. I took the intake manifold off of mine and sure enough, all but 2 were clogged. I cleaned them out and the van ran like new again and has been running that why with almost 200,000 miles on it. I am wondering if this is what is happening with my truck now. The van threw trouble codes though. I haven't had a CEL yet. I started the truck the other day and it ran like it was missing a 3 cylinders for about 5 minutes then it smoothed out. That is the second time that has happened but no CEL. I didn't drive the van enough to compare the early symptoms and my wife waits until the thing nearly dies before she tells me there is something wrong with it.
I would guess that checking the fuel pressure at the rail would be a why to see if the fuel pump is working correctly. I would probably take it to a mechanic for that as I have neither the knowledge or the gauge to check it myself.
I will keep you posted if I figure anything out.

PS. Noticed the mrcessna in you mail address. I take it you do a little flying?

 

I may try looking under the intake for the EGR stuff...i know i probably don't have the tools necessary..but it is worth a look..then fuel pressure will be next I guess...Yeah, I actually fly for a living..I am currently captain on a Learjet 25..and right seat in a Hawker 800XP...you fly too? Let me know what you find on your truck..and i will do the same

 

I have a 99 F150 4.2 that was having the same trouble new plugs, wires, filters, coil pack, fuel pump, sensor after sensor, and took it to garage after garage done it for about 3 years finally broke down put a brand new engine in the truck it had over 300k on it was starting to leak oil after the brand new engine was put in still had same problem I finally gave up on the garage's and dealership's done a few test myself and put my brain to work to find out that the only problem was a 50 dollar fuel pressure regulator located on the fuel rail back left corner top of engine hat the same problem out of a 95 nissan also and it was the same part hope this helps