It seems one mechanic, 2 muffler shops and 1 Ford dealer can't figure out my low rough idle, at least not with technology anyway. I know I've posted on this before so please don't lecture me. The symptoms are after warmed up, it idles low (500) or below and some roughness. In park if I press the accelerator its a little rough up to 1000 and seems to smooth out a little but after letting off the pedal it idles rough from 1000 back to 500. Truck has never thrown a code. Starts up no problem and always idles good upon any start up. I can start it 10 times in a row after warmed up and it always initially idles good for a min or so but settles back down to low and rough. Took it to mechanic and Ford for diagnosis. Took it to muffler shops for cat issue, lack of power and recent sulfer smell. They did their own diagnosis before doing any exhaust work. Excuse my laymans terms but the muffler guy showed me live data and what I"ll describe as a monitered heart beat. The passenger side looked great. The driver side looked flat lined per say. His analogy was that the driver side was having too much fuel dumped into it for whatever reason and causing the cat/sulfer smell issue etc. Everything else looked "good" just like my mech and Ford told me. In other words they don't know whats causing my problem. The muffler guy told me to replace my new driver side upstream 02 sensor which I did to no avail. Of course I can't do anything to my exhaust if I need to without first knowing without a doubt that I won't fry any new cats. Here is what I have done so far, some for maintenance and some to try to solve this problem. 2004 FX4 5.4, 100k miles. New MC plugs and cops. Refurbished injectors, New fuel filter, New air filter. New throttle body, New fpdm under spare tire. New vct selonoids, new upsteam 02 sensors. Cleaned Maf sensor. Changed oil, tranny fluid, antifreeze and new thermostat. Fluid levels all look good. Truck otherwise drives ok but lacks power due to exhaust issue which I think was caused by previous owner not addressing a misfire or something. Also Ford reflashed my Pcm. Did the so called relearn and have driven this truck at least 1000 mi since then. My question is: Whats left? Im at a dead end quite literally. Do I have a real issue that is possibly damaging my engine and exhaust? I can't throw anymore money at this freaking truck. Am I missing something?, Does all of this mean anything to anybody? I've even checked high and low for vac leaks. Its absolutely driving me nuts and i know not everybodies idle problems are the same but for the Love of God if several proffessionals can't figure it out then what is a DIY weekend mechanic like myself supposed to do. Im sick of staring at the engine bay waiting for devine intervention or something. I think I partly posted this to vent but if anybody dare try to talk me off of the ledge I welcome it with open arms. I forgot to mention that the truck does have an aftermarket remote start if that means anything, came with truck. Have a good day guys.

 

Never done anything with the injectors, but do you possibly think that the refurbished injectors could be partly to blame? An excessive amount of fuel could be due to an injector stuck open, have you pulled any plugs to see the condition of them since the change? I would check the drivers side plugs where you are having excessive fuel issues...Just my 0.02 but I don't know what else it could be and I am in no way a mechanic but it seems you've covered the standard problems...

 

Im pretty sure it was doing it with the old injectors too however all of the injectors flow tests seem to be ok but I am starting to not trust these diagnostics. I have yet to pull a plug on that side because I had no idea that side of the engine had this issue until the meineke guy showed me. I had it at Ford the previous week and they said everything looked good so this might be a new issue for whatever reason. My fear is that I"ll pull a plug and it won't look good and confirm what I already know but still won't know the cause. Maybe it is an injector. I think there is a way to determine that but lifting the fuel rail and looking for flow where there should be none. The meineke guy swore it was my 02 sensor because it tells the computer to add-subtract fuel but new one didnt help. Im almost thinking it may be an electrical problem between the PCM and that 02 sensor or my pcm in general. Thanks for your thoughts