I have a 2001 Ford Expedition with 119,000 miles on it. I noticed a small what feels like a misfire at idle, fuel smell when it's cold, and big clouds of blueish colored smoke at cold starts. So I took it to Mike Naughton Ford and they said it was a fowled plug. $512 later, the plugs and boots were replaced and the problem still exists. I took back to them and they said they did notice fuel dumping out the exhaust at cold start, but the computer and diagnostics showed everything was within specs and sent me away. I replaced all 8 injectors, and cleaned the MAF sensor, checked all the vacum lines and still no change. So I took it to a small local shop who was willing to spend more time diagnosing things. The god a P0172 System to Rich Bank One The long term fuel trim on B1 is 10.15% on B2 - 4.68% Short Term fuel trim switching + ___ - 1.5%. They tested Oxygen sensors, voltages were good and switching fine, two compression tests and all 8 were ok and they determined it may be a leaking injector. I replaced all the fuel injectors before I took it into the shop so I was pretty sure that wasn't the problem but let them do their testing anyways. No leaks were found, the fuel pressure KOEO is 40psi., pressurized rails multiple times, no drips or leaks. System held 20psi. over night. In the end they said they agreed that something was definately wrong but were unable to determine what and sent me home $282 later with no fix in site. The only thing they could tell me is that it would need to fail before they could figure out what was causing the problem. I have a warranty on the vehicle, but if nobody can figure out whats wrong or admit there is a problem I can't keep throwing money down the drain for diagnostics. If you have any advice I would greatly appreciate it.
Get a noid light. I have seen injector drivers stick on and hold the injector wide open. The light is available at you local auto parts store such as autozone. It plugs into the injector plug and while running you should have a a flicker of light which means the injector is getting the proper pulse signal. If one is brighter than the rest or solidly lit, then the ECM is bad. I have had 2 different vehicles do this, but they stuck wide open. It was ugly!!
Oh, by the way, welcome to the forum. Good luck on your repair.
I'm moved this the the fuel/efi system so you might get better replies.
So I replaced the PCM, IAC Valve, and had a leak down test done. The leak down test showed all the cylinders between 160 and 165. I also had the temperature sensor checked with an ohms meter and it showed it was working properly as well. There is still a misfire and it's still dumping fuel! I see nobody has responded to my ad here with any suggestions so I guess I'm going to start posting on other forums to see if I can get any more suggestions.
The misfire is constant, but not extreme. You can notice it sitting at idle, but it's not a constant. That's why I had the leakdown test done because I assumed it was valve seals as well, but the test came back ok and they checked all the plugs when they pulled them and they apparently looked ok as well. I'm guessing it may be an electrical short at this point since I've tested everything mechanically at this point.
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