I have a 96 Bronco with a 351 in it. The checkengine light is on and it has a trouble code of PO443 also the Overdrive light flashes and the engine seems to surge at 1200-1500 RPMS. The sirge quits if I plug the egr. Anybody have any Ideas of what to check? I have checked the VMV and it has the correct ohms resistance.

 

P0443 Evaporative Emission System Purge Control Valve Circuit

"96 Bronco / 5.8L" and its OBD II? Live in California perhaps?

And just so we're all clear what exactly are you referring to as a "VMV"?

 

Does not matter where you live in the US, all '96 Broncos are OBD-II.


VMV = Vapor Management Valve. It's a fancier CANP solenoid.

 

Thought that was rather familiar, you should have returned to your existing thread rather then start a new one.

Previous thread same issue link,

https://www.ford-trucks.com/forums/1...-to-start.html

likely reason you got no more answers is you gave nothing else to go on, thread died off.

What was the results of clearing the computers memory of all codes?

Safe to assume now 0443 returned?

O/D light still flash on and off or?

Have you recently been off roading? Driven over/through heavy brush? into/through any deep water/mud holes/heavy pouring rain etc?

 

I ran jumper wires to the VMV and it opened the solenoid letting vacuum thru. I also warmed the truck up and put a test light to the ground side to check when ground occured when I revved the motor to about1500 RPMS the light came on. The red wire going to the valve does have power going to it.

You state it opened the valve but how about vacuum present when it does, any vac at its source?
Computers gotta have a way know it actually opened, measured change in valves value or measurement of actual vacuum flow stop/start/stop.

Might simply be the valve is "bad" even thought it physical opens, computer doesn't detect it has. Doubt it has a thing to do with vac flow but can say for sure all ours of this series around here? they are OBDI system.

 

My Ford Service Manuals show they are OBD-II and everyone one I know at FullsizeBronco.com with 1996 Broncos are OBD-II. Like everything related to Ford, there is always something to disprove the theory....

 

Ahhh worded that wrong, attempted say the vehicles we have/own between all of use here this series are all OBDI variety. OBDII in one a rare bird around here, not unheard of no but pretty rare.

The book I have covers all models Bronco/pickup 1980 tru 96 but shows nothing of the OBDII system, nary word about it.

I did look at a F-250 for sale up the road couple years back, a 96 and it was OBDII.
Had a busted front axle arm, I wanted it even willing to pay a premium for it but the guy wanted way to much for it, wanted more then it was worth even if its axle wasn't busted and its interior wasn't trashed.

 

No the truck has never been off road. Use it only on weekends and it just started. The O/D light stops flashing if I pull the wire off the VMV. Are there wiring schematics somewhere online so I coul follow some of the wires?

 

Check your other thread....https://www.ford-trucks.com/forums/1...-to-start.html

Finding free wiring diagrams for this vintage truck is a little tough to find. I purchased some EVTM CD copies from E-bay.

Your troubelshooting is starting to point at a bad VMV valve. Perhaps it is breaking down under load and pulling down the supply voltage? As I mentioned in your other thread, the supply voltage source for the VMV and transmission solenoid pack are the same.

 

All the VECI labels listed at Motorcraftservice.com for 1996 Broncos show all of them are OBD-II.

I have the same book as you, no OBD-II....

 

I got a used VMV at a yard and it does the same thing. I thought even if the used one was bad it would do something different. Is there a way for the EGR solenoid to steal the voltage. Since when I pull the vacuum line off it the motor stops surging.

 

The EVR (EGR Solenoid Regulator) is also in the same circuit as the other items mentioned before. The EVR is modulated on and off by the PCM. I would start metering that supply voltage to see if it is being pulled down or perhaps there is significant ripple on it.

I have a seen a few cases of intermittent O/D light flashing with no codes to be caused by a bad alternator. Usually caused by too much ripple on the output. Maybe there is a connection to that and your P0443 problem?

 

The reason I think it has something to do with the EGR is it surges worse when the engine is cold and what I hear the EGR shouldn't function until the motor is warm Which sensor tells the PCM to turn on the EGR. I have replaced the heat sensor on top of the thermostat

 

It's a combination of ECT and TPS, perhaps the Engine RPM comes into play as well. Once the engine is warmed up and light load cruising is the only time the EGR should be active.

 

Still needing some help. I have replaced the vapor management valve, the ect sensor, the throtle position sensor egr pressure sensor and ran every wire I can think of. Even took to the dealer for diagnoses they said it had the original code of po443 and a transmission code of po713. The only common thing I can find in common is a gray and red wire that hits a bunch of things.