Ford F150 4.2

James Williams · Jul 25, 2012

After the first 10 miles while driving I get dentonatin,or valve plng,mostly at high RPM when Im on the throttle,Ive cleaned the PCV valve,checked the MAF.Im to the point of wandering if I have a manifold leak.I checked the codes and they are PO 171 & PO174,need your help,Seemed like it started all at one time,its 175,000 miles on the motor.The truck Idels and runs good

jimmy

wisbaker · Jul 25, 2012

Had a similar problem on an 01 F-150 with the 4.6. Problem went away when I changed the fuel injectors, I suspect one was not passing enough fuel and the cylinder would get to lean and she'd knock. For what it's worth Ford couldn't diagnose it and my dealer claimed it's normal and they all do it. Goggle the codes they might tell you something it might have something to do with a temperature sensor so the computer is not setting the right fuel mixture when it's cold.

robgIN · Jul 25, 2012

those codes are for lean bank 1 and 2, so most likely a vacuum leak, pcv hoses and elbows are the most common problems. With that many miles could be upper plenum gaskets getting hard and leaking also. The egr on that engine goes into a port along the center of the intake and it has orifices into each port. Those orifices tend to plug with carbon over time and block the flow of egr causing ping, many times all but one or two port will be completely plugged and all the flow goes to 1 cyl and it feels like a miss.

Ford F150 4.2

James Williams

Well-known Member

wisbaker

Well-known Member

robgIN

Member

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