Tommy J

Im having zero luck with my low idle problem so I thought I"d throw this out there to see if its related or not or a seperate issue. 2004 FX4 5.4 98k miles. This is happening consistently now, After the truck is warmed up and driven for a while and parked, when I come out to start it, it wont start on the 1st try but starts right up on the second try and on average I would say it has to sit 10 min or so while Im running errands etc. I have tried starting it immediately after I park and shut it off and it starts right up. Other current symptoms are low idle with a little random roughness at idle, never stalls. I've replaced plugs, cops, fuel and air filters. Cleaned the TB and MAF with appropriate cleaners, refurbished injectors, played musical chairs with new cops and replaced FPCM. Checked and rechecked all connections and looked for vac leaks. Never has thrown a code. Was told by "Ford " guy I somehow fried my Tb during battery and pcm disconnects during my plug change etc. Took it to my mech and came up empty, don't really know how good the guy is because hes new to me. Short of me going Joe Pesci from casino on it, Im at my wits end with this truck. I know some things but get a little lost with technical diagnosis. I know I"ve beaten this topic to death on this site but Im hoping that Im just missing something and someone will say bingo, I know what your problem is. Thanks

screamineagle

It sounds like your losing fuel pressure. I believe there is a pressure switch on the fuel rail that could be the culprit. Not sure on how to test it, but I remember some talk about this on another thread.

Especial86

iTrader: (1)

I'd try the TPS sensor.. If that doesn't work than a new throttle body may be just the ticket..

How old is your battery?

Tommy J

I was kind of thinking the same thing. I keep suspecting fuel pump for some reason but I"ll look into that fuel rail switch

Tommy J

Not sure of the battery age cause the truck is "new" to me but you would think that as many times as I disconnected it I would have at least checked it. Im ready to do the TB if I keep coming up empty and then fuel pump. Of course its freaking snowing here in the N. east right now and its been cold as heck. 2 Ford guys have said TB and Im just wondering why they are so sure about it from just hearing symptoms. My fuel filter was dirty as hell and Im wondering what they may have done to the fuel pump if it affects it at all. Worst case scenerio I"ll have more new parts and sell the old ones. thanks

Especial86

iTrader: (1)

The TB is arguably considered a wear item.. It's got a second TPS sensor on the servo motor side that cross references with the TPS on the passenger side.. If one TPS is off a bit it can cause random stalling, surging, and low or high idle... The servo side TPS is cheaper to replace by just buying a whole new TB, but it's less likely to wear out like the other (passenger side) TPS.. That's why I say change that first....

Another check would be to run the motor with the AC, and lights running.. If you see an even worse idle present, or no change in idle, you may have a resistance issue (bad connection) somewhere between the alternator and battery.... Your idle should raise up a bit to compensate for the load from accessories, if it doesn't I'd suspect an alternator, poor ground or battery issue.. Have the alternator and battery tested if you find good clean connections everywhere..

Tommy J

First of all let me say that every time I see that pic of Keanu I freaking crack up. I will poke around some more after I shovel out and check batt, alt and such. I am torn between just a tps or whole TB because I think I can get a tb for $160 from rock auto with a new tps. I can always just put the new tps on the old tb just for curiosity sake and if its just that then sell my old tb with the knowledge that the tps is bad. If a new tb was like 300 or something I"d go the tps route. Thanks for your input

Tommy J

Ok, so no change in idle that I can tell after turning on ac/lights. Battery putting out good power and visually checked connections to alt and frame ground. I forgot to mention a kind of weird thing. On a few occassions when Im starting the truck, looking around and shutting it down and restarting etc, it has started immediately when I turn the key, I mean instantaniously with not a hint of cranking first, I mean instant start up like an electric toy car would. Turn the key and not a second of cranking, just instant start. has done it about 4 times in the last week and it always happens after warmed up and Im messing around with it. The truck does have an aftermarket remote start that I barely use and has not given me a problem