Expedition repair
Asked by Guru1XV13 Sep 01, 2019 at 01:46 PM about the 2008 Ford Expedition King Ranch
Question type: Maintenance & Repair
I have a 2008 expedition 5.4 that runs rough. On
acceleration it will bog down as if it's not getting
fuel... at 100% throttle it doesnt go anywhere and
starts popping thru the intake I do belive. I've
replaced fuel filter, air filter, crankshaft position
sensor, intake runner control module, coils &
plugs. The injectors spray fine and fuel pressure is
good I'm thinking about upstream 02 sensors next
cats were done in march.... any help is appreciated
and the only code I ever had was for intake runner
control module
14 Answers
ImFlammable answered 5 years ago
The fuel pressure test should be done under load not at idle... rev the engine up as quickly as u can and make sure pressure doesnt drop
ImFlammable answered 5 years ago
Low power conditions under heavy throttle like this are going to be fuel related or a restricted exhaust or timing problems. vacuum leaks and o2 sensors wont cause this
Ok I guess I'm going to look into timing then. Thank you for the info
They were just replaced in March... I'm going to check the temp just for the hell of it though
ImFlammable answered 5 years ago
The o2 sensors are not used to trim fuel at full throttle. The mixture needs to be richened up not leaned out. The sensors will still produce a signal tho
If you did not fix the cause of the last ones going bad the new ones could already have gone bad too. A back pressure test is best. If there is a bad misfire it will ruin the cats!
ImFlammable answered 5 years ago
Upstream O2 sensor data under heavy throttle can be used to identify direction. High voltage above 450 millivolts suggests it is not a fuel issue but possibly a exhaust restriction. Extremely low volts < 0.100 millivolts suggests its not getting enough fuel
There isn't a misfire though I disconnected a couple coils yesterday while running to check with test light because I replaced some pigtails and wanted to make sure they were wired right and only then did it throw a code which immediately went away
CITYLIFE404 answered 5 years ago
Do u have a code reader to scan for codes. Shooting parts at it usually gets expensive fast.... check for misfire codes and other related codes... and at wide open trottle the O2 sensors are disabled. So it can’t be that. Clogged cats are possible and sometimes they don’t set a code.