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Racking my brain trying to find the source of the problem. Replaced fuel pump and filter (did have a fuel delivery issue due to weak pump). Replaced the PCV valve, hose (and elbow) and another vacuum line that were badly worn but not leaking. Smoke test found leakage at cap at top of idle speed control motor(?)..sealed temporarily with silicone to resume tests..cleared codes, ran vehicle and upon shutting off heard vacuum leaking from the Vacuum Regulator Solenoid. Can this small draw of vacuum trip lean codes on both banks? Really trying to avoid intake gasket job!

Sorry Reynaldo, last post I said it was the DPFE...was in fact the 'Vacuum Regulator Solenoid'
Vehicle: !998 Ford F150 4.6L
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yes by not properly controlling egr due to and or venting vacuum ; all of this while engine running. can also cause ac to deflect to defrost vents in some older explorers / mountaineers.

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The DPFE uses exhaust not vacuum.  Clean the MAF and use brake cleaner that Ford recommends and retest.

 The DPFE uses exhaust in order for the EGR to work

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