Howdy All

I have a new set of ODBII codes to diagnose in my '96 FSB, 5.0 5 speed.

402 = EGR Flow Excessive
1401 = DPFE High Voltage

I recently replaced the DPFE and removed a "Restrictor" that had been put in by the PO or their mechanic. I also replaced the EGR valve because it was so clogged with crud that I was sure that it had not worked in a long time.

It looks to me like these two codes are related, and probably related to the new parts, but I'm wondering if they are not pointing to a different problem at a different point in the system that I need to check. This Bronco sat for a couple years and I don't have any information about how it was maintained prior to that with the previous PO.

Any suggestions about what these codes might be pointing to is appreciated.

Thanks.

 

Have you cleared the computer memory since you replaced those components? The Codes would tend to indicate a stuck open EGR valve. Make certain the valve is mechanically sound and actually opens and closes as designed. Apply vacuum and or carefully slip a small tool into the valve below the vacuum diaphragm and make sure the pintle moves/drops back into the seat. Be careful using the latter method. It is easy to slip and puncture the vacuum diaphragm... but then you would know for certain that the valve is bad. ;-)

 

Thanks Greystreak
Yes these are new parts and I did clear the codes before driving with the new parts installed.
This Bronco sat for a couple years before I bought it and I have been suspicious of the exhaust system since before I brought it home. If I understand the basic operation of the EGR system, it all starts with proper back pressure in the exhaust system, correct? IF that is correct, then could the exhaust system, (CAT), be plugged enough to create extra back pressure but not enough to cause noticeable problems otherwise?
Is it time to bite the bullet and get the Magnaflow exhaust?
Thanks.
Ron

 

Exhaust Gas Recirculation is regulated by engine temperature and HEGO (O2) sensor information (which translates to fuel-air mixture as designated by operational conditions). There is nothing that "reads" exhaust system back pressure. However, with that said, excessive restriction in the exhaust system will create changes in HEGO sensor reading that will ultimately affect many operational parameters including the EGR system. (Now if you want to tell the wife or significant other that the new exhaust will add value and benefit the overall efficiency of the truck, I can't stop you.)

In short, the EGR only operates when the engine is operating efficiently enough to handle having some exhaust gasses redirected back through the combustion cycle.

 

Have a 95 bronco with a 5.0, with a rea curing 334 code. Have Vaccum present at idle between .90 to .76 volts at the evp. Replaced evr and didn't change anything. Any thoughts?

 

Thanks again Greysrteak

I am wondering if through my own ingnorance of these systems I'm missing something obvious here. If the EGR system operates based on Engine Temperature, then if the engine temperature sensor's, or O2 sensors, are getting flaky, is it true that we could be seeing the EGR system operate out of it's parameters and throwing codes with the source being the temp sensors, not the EGR system?