Rough Idle - No Codes
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Junior Member
Joined: Jul 2015
Posts: 17
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Rough Idle - No Codes
Been fighting a rough idle issue. replaced the plugs and coils with OEM parts. replaced the coils a second time. Also replaced the MAF.
2008 F-150 5.4L
when accelerating
If I give it 100% throttle, it just bogs down
I've suspected O2 sensors
here is some data from the truck
B1S1: .60v-.800v // 0%-2.0%
B1S2: .135v-.675v // 99.2%
B2S1: .050v-.830v // 24.6%-28.5%
B2S2: .607v-.887v // 99.2% (flat graph at idle - voltage dives DOWN with acceleration)
MAF 1.00-1.14
EVAP 39.2%
Fuel Pressure: 40.1PSI
2008 F-150 5.4L
when accelerating
If I give it 100% throttle, it just bogs down
I've suspected O2 sensors
here is some data from the truck
B1S1: .60v-.800v // 0%-2.0%
B1S2: .135v-.675v // 99.2%
B2S1: .050v-.830v // 24.6%-28.5%
B2S2: .607v-.887v // 99.2% (flat graph at idle - voltage dives DOWN with acceleration)
MAF 1.00-1.14
EVAP 39.2%
Fuel Pressure: 40.1PSI
Senior Member
Joined: Oct 2016
Posts: 3,702
Likes: 766
From: Parts Unknown
Unplug MAF and see if the engine runs better. May require cleaning. O2 sensors are likely doing their job. If the engine runs rough when you first start it cold, I doubt the O2 sensors would be bad.They are not in the equation during the first few minutes of cold starting.