Revving/stalling/surging issue on a 1997 XLT 4.0L.

[3Dee]

Hello all, hoping someone might have some helpful information about what's going on with my Aerostar.

Ever since I bought it in 2019, Its had an issue. Not the biggest one, but it has been very annoying.

The idle of the van is constantly fluctuating, revving over and over, with small periods of high (but smooth) idle. The main problem with this is: when slowing to a stop, if not done very very smoothly, the van will do the revving over and over, and most times stalls the entire vehicle, requiring a switch to Park, and a restart of the van. Other than this, the van has given me no other problems, and to this day is the best $500 I've ever spent.

Things I've Tried:
Replaced O2 Sensor (Front and Back)

 

[BrooklynBay]

Check the TPS for dead spots with an Ohmmeter, clean the idle air control valve (Ford calls it the air bypass valve) the snap on filter on that solenoid valve, check the vacuum hoses for leaks, clean the throttle body, and the mass air flow sensor. The throttle body & MAF sensor use different sprays. Are you getting any codes such as P0171-P0174? That could be related to leaking manifold gasket seals.

 

[zenish]

my 4.0 van does this too.i always shift to neutral coming to a stop.the check engine light is on sometimes.

 

[BrooklynBay]

Check the code to see why the light is on.

 

[zenish]

Check the code to see why the light is on.

i still haven't had time.its progressed to having to hold the gas pedal down slightly while stopping.

 

[zenish]

i still haven't had time.its progressed to having to hold the gas pedal down slightly while stopping.

the code reader says right oxygen sensor quit switching though it only seems to have one.its running MUCH worse now.new sensor arriving from rock auto thursday.

 

[zenish]

the code reader says right oxygen sensor quit switching though it only seems to have one.its running MUCH worse now.new sensor arriving from rock auto thursday.

and now code 14.and code 41 still.