Hey fellas, it's been forever since I have posted but I am having some trouble and am looking for some insight on what might be wrong with my truck... Truck: 2003 F150 4.6L W 2wd Mileage: 215,000 on the body, 60,000 on the motor. Symptoms: runs extremely rough at idle, exhaust gases might as well be straight fuel dumping out (from the smell), will drive rough while cold but once warm will stall out while in drive or reverse. So basically once under a load it stalls (after the truck is warmed up) but will stay running in park and neutral. Only codes I have are downstream O2 sensors because, well, they aren't there anymore... Also monitored live data just at idle and my fuel trims were horrendous... I will attach pictures of some live data. I recently replaced the intake gaskets due to a suspected internal coolant leak and had the time now that this isn't my daily anymore, but I already pulled the intake manifolds again to ensure that everything was installed correctly and no wiring harnesses were pinched in the process. Reinstalled everything and no change. Things done/tested so far: Cleaned MAF and disconnected while running, worked fine. Replaced upstream O2s, replaced PCV hose that goes to back side of TB, sprayed down entire top of engine for vacuum leaks, full tune up about a month ago with platinum plugs, cats have been gutted (started clogging a while back), replaced ECT sensor (or CHT sensor, the one on the inside of the valley under the intake on the drivers side). I have been doing some research and the people with similar problems fix theirs with something I've already done. I am wondering if maybe my EGR valve is stuck open? I've had a code for the EGR since I replaced the motor but it never cause an issue so I didn't pay much attention to it. I'm sure there is more I could list and I will add it as I remember. Sorry for the novel! Just trying to be as specific as possible. Any insight is greatly appreciated! Thanks in advance! T
IMO, sounds like the IAC (Idle Air Control) Not that I'm golden on this, let more member's opinions come and comment. You can take it off and check it, see if it is moving during startup and while idling, it should move or make buzzing sound, cover the port safely (big clean shop rag) during test. RockAuto has one as low as $34.99 3-5 day shipping. Airtex/Wells part #4J1076 http://www.rockauto.com/en/catalog/ford,2003,f-150,4.6l+v8,1434761,fuel/air,idle+air+control+(iac)+valve,6072?a=Referer+www.google.com+URL+/en/catalog/ford Autozone's is $93.99 part # TV290 Ship to home only option $68.99 Advance is $93.99 part # 50619 Ship to home only option $53.99 Don't forget the gasket.
Thank you for the in depth insight! I replaced the IAC a year or two ago but it was howling pretty good at the time. I'll pull it off tomorrow to check if it's either faulty or dirty and sticking. Correct me if I'm wrong, but the 10th gens don't have a coolant temp sensor per say but a cylinder head temp sensor instead? I'm wondering if I have something else wrong combined with a bad CHT sensor. There is obviously something causing it to have the rough idle, but the fact that it gets worse and even stalls out once the truck is warmed has me wondering if the ECM is reading the motor as "cold" when it's not and throwing everything else off enough to stall it out under a load (in drive)?
Well I removed, cleaned, and inspected the IAC. I didn't see any issues and seems to be working fine. But I did decide to unplug each coil one at a time with the motor running to make sure that every cylinder would change the idle. All but 2 had drastic differences. The other 2 had actually seemed to smooth out the motor! I pulled one of the coils and it smelled pretty burnt... I'm going to replace those 2 and see what happens. I can't complain, 7 of the 8 coils are original OEM with 215,000 miles on them... not sure how in the world they made it so far, but it's about time! Too bad they aren't cheaper...
Check ebay pricing on those coils. Not 100% on the CHT with That year 4.6. Galaxy S4 Cetane Powered Android
Well I think everything is good to go. I went coil by coil and unplugged each one while the truck was running. Keep in mind that there are no misfire codes, so I was basing this solely off engine performance. All but two of the coils made the truck run worse and if anything once unplugged, those two made the truck run better! So I got a couple of coils from Napa for $25 a pop. I think another problem that I'm having is that a hand full of the locking tabs on the connectors for the coils are broken so over time they back off and the connection causes an intermittent misfire. But put roughly 20 miles on the truck with no issues! Thanks Roush PSD Interceptor for the input!!
Way to go on the self diagnosis. Maybe you could find those COP harness ends at a pull-a-part yard and replace them. Or the entire harness if your not good changing the fiddly terminal ends. Sent from my SM-G930P using Tapatalk