Jbrew

Sounding like a broken record, but I'd fix that plug first since that could be the root.

If you would like to continue on this route, this a good site. There's a lot of hiden info on this site, but it's good once you learn how to manipulate lol, -

http://www.fordscorpio.co.uk/mafdata.htm

Carcrazygts2

When its running poorly have it scanned by a shop with a something better than a handheld scanner. Its no going into closed loop. Does the truck have any codes that are current, pending or in history?

escodsm

These come and go:
P0136 O2 sensor circuit bank 1
P0156 O2 sensor circuit bank 2
P1401 DPFE Sensor circuit high
P1131 O2 sensor
P1151 O2 Sensor

These are persistent:
P0171 bank 1 lean
P0174 bank 2 lean

escodsm

Just took the IAC off, it was filthy, but also the pintle appears broken. It was not sealing against the other chamber. Should it be closed at startup, then open up? Or the opposite way around. Because with it reset it is basically wide open. I tested it with my multimeter and got 9.6ohms.

Jbrew

Oh brother

I need a vacation.

escodsm

JBrew I figure it's probably what - 11 hour drive to get here? You could help me and not deal with the forum bs!

Jbrew

ROFL

escodsm

I'm doing my due diligence JBrew - first I removed the IAC and tested it on the bench, its at 9ohms so that is within spec.
Let it soak in carb cleaner. My only concern before I put this back on, is that it appears "Open" for a start condition but there isn't much travel to the pintle. Almost like the spring doesn't have enough to push it back

escodsm

here is the gap with the IAC ready for ignition/start up. Makes sense, if the goal is to add more metered air at startup.

Thing is, it doesn't really move much at all from this position. I can't find a reference picture like this of a Good IAC so have nothing to judge it against like JBrew judges me lol.

Carcrazygts2

Replace both front oxygen sensor. More than likely that is the main culprit