96 Bronco check engine and failing NOx

[lazyflower]

Recently got a 96 Ford Bronco but can't get it to pass emissions (NOx and check engine light was on). Has a rebuilt 347 stroker that was put in in 2007 but only has about 20k miles on it. I cleaned the old EGR valve and had the rest of the system checked out and the mechanic didn't find anything wrong. I get a P0402 error (Exhaust Gas Recirculation Flow Excessive Detected). I've also had trouble getting the AC (I've tried a recharge and it seems to keep pressure), not sure if that's related or not.

Any helpful advice?

 

[miesk5]

Yo L,
Welcome!
DTC PO402, PO401, P1400, & P1401; Usually the failure starts with an almost imperceptible surge while cruising. Gradually it develops into an annoying surge and then the check engine light comes on... Early versions of this part had an aluminum body - this plastic part is an update, and is much less failure prone that the early aluminum part..."...When OBD2 came along, the EPA said that we now have to be able to know if the EGR valve quits working and turn the check engine light on if it does. Ford chose to do this by installing a slight restriction in the tube that brings exhaust to the EGR valve. Now we all know from science class that when there is flow through an orfice, there is a pressure drop across it. So Ford installed a pressure sensor across the orfice - when there is flow because the EGR valve opened, the pressure sensor senses the flow and tells the PCM the system is working. That's why they call it a Differential Pressure Feedback EGR Sensor! Now, what do you think happens when you run hot exhaust gas into a little electronic sensor? It does not last too long.."

"...The EGR system is monitored for undesired EGR flow during idle. The EGR monitor looks at the DPF EGR signal at idle and compares it to the stored signal measured during key ON and engine OFF. The test fails when the signal at idle is greater than at key ON engine OFF by a calibrated amount.
EGR valve stuck open
Plugged EGR vacuum regulator solenoid vent
Plugged EGR tube
Slow responding D.P.F. EGR sensor
Damaged DPF EGR sensor
Improper vacuum hose connection to EGR valve or Plugged vacuum hoses
EGRVR circuit shorted to ground
Damaged EGR vacuum regulator solenoid
Damaged PCM
A DPFEGR PID reading that is greater at idle than during key ON and engine OFF by 0.5 volt or a rough engine idle, may indicate a hard fault..."
□○□
ASAP, find out if speed control recall work, if equipped was completed @ Recalls Look-up by VIN (Vehicle Identification Number); or @ Welcome to Ford Owner | Official Ford Owner Site; or ... have VIN ready. While there, see most Ford dealer maintenance/repairs done @ any dealership nation-wide.
"Summary: ON CERTAIN PICKUP TRUCKS, PASSENGER VEHICLES, SPORT UTILITY VEHICLES, AND MOTOR HOMES CHASSIS, THE SPEED CONTROL DEACTIVATION SWITCH MAY, UNDER CERTAIN CONDITIONS, LEAK INTERNALLY AND THEN OVERHEAT, SMOKE, OR BURN. THIS COULD RESULT IN AN UNDERHOOD FIRE."
To confirm current status, use this guide by jowens1126 @ 93 & 94-96 Cruise Control Recalls Repair
Note that the 93 recall is different than the 94-96 recall

Here's the 1996 Bronco/F-Series Workshop Manual partial

96 Bronco Owner's Guide, Maintenance Schedules & Parts and Accessories by Ford @ Owner Manuals | fleet.ford.com

96 Bronco Dealer Brochure @ 1996 Ford Bronco Technical Info pictures, videos, and sounds | SuperMotors.net ... scroll down

96 Bronco Quick Tips Brochure Excerpts & some Eddie Bauer options @ 1983 Ford Bronco 96 EB Bronco Brochures pictures, videos, and sounds | SuperMotors.net

Register to see most Ford dealer maintenance/repairs done @ any dealership nation-wide @ Welcome to Ford Owner | Official Ford Owner Site .



Al