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1999 Ford F-150 Question: I keep getting the code PO174 for My'99 f150 , 4.2 v6 motor.



dukemooner, 4.2L V6, Henderson, NV, December 04, 2012, 07:52

I changed all O2 sensors, cleaned the MAF sensor and checked for vacuum leaks.Is there a test to check the MAF sensor?
The truck still runs rough at idle and pings every now and then.
Please help.

2 Answers
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  • Answer #1

    Greg's Orange Auto (15229 Answers) , Orange, CA - (714) 361-9386
    globalhelper December 04, 2012, 09:03

    did u have a smoke tst done? need to read fuel trim with scanner. these are known for intake manifold leaks and intake runner leaks. you can test msss are flow with a test but only for grds and signal with volt meter

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  • Answer #2

    December 04, 2012, 09:43

    Agree with 1 the pcv hose on rear of intake i bet is the trouble. Hard to even see, just fixed one
    I pulled the intake to do the work but there was other repairs i needed to do.
    It may be accessable otherwise! Intake leaks are common too. Same code in this one and this fixed that also, the hose turns into mush
    and then leaks vacuum.

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