2019 Expy XLT, 136K. During my test drive after installing new timing chains and tensioners (P0019, P0018, P052C, Bank 2 timing chain slipped a couple of teeth on the crank sprocket), while my AC is set to manual, dash vent, recirculate/Max AC, the blower will surge and blow through the defrost windshield vents momentarily during hard vehicle acceleration.
It's never done this before and curious if any fellow members have experienced this and how it was fixed. I'll be hooking up Forscan tonight and follow up here later.
thanks in advance, 11b4v.
There was probably a vacuum check valve in the vacuum supply that was damaged or disconnected during the work. OR - an IWE vacuum line damaged or left disconnected.
The vacuum check valve prevents a momentary loss of vacuum to the HVAC system. A leaking IWE vacuum line will cause vacuum drop on hard acceleration.
I had a 2015 Expedition Limited 4x4 that would momentarily default to the defrost vents when driving uphill and lifting my foot from the accelerator pedal, just as the transmission felt like it had upshifted.
Ford issued a TSB instructing the dealer to replace the IWE vacuum check valve, which would eliminate the issue. It also caused the 4WD system to “clack” as it tried to shift in and out of the 4WD, due to the vacuum drop.
I left my vehicle at the dealer for a week (under warranty) and they said they could not duplicate the issue. On my drive home, the problem recurred.
I found the TSB on line and replaced the vacuum check valve myself, which fixed the issue.
On my model, the. IWE vacuum check valve was on the firewall, left (driver) side, inline with the IWE vacuum solenoid. The new check valve was blue, and the original was white.
If the check-valve doesn’t fix the issue, check all of your front plastic IWE engagement vacuum lines closely for damage and/or proper connection.
