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

50

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

50

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

They were just replaced in March... I'm going to check the temp just for the hell of it though

50

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!

50

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

9,085

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.

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