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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / May 200597 F150 EGR Insufficient Flow - DTC P401 (EGR Vacuum Regulator solenoid)
Greetings, I wanted to run my troubleshooting steps past some of the more experienced. I have a 97 F150 4.6L throwing a P0401 (EGR insufficient flow). I think I have a bad EGR Vacuum Regulator solenoid. I've disconnected the green vacuum line from the EGR Vacuum Regulator solenoid to the EGR valve and applied a slight vacuum to the EGR valve. The engine RPMs down almost stalling. I'm guessing the EGR value is okay. Reconnected. Moving to the EGR Vacuum Regulator solenoid. After engine warmup, I checked the voltage on the EGR Vacuum Regulator solenoid connector. It showed 12-13vdc. I assume that means the EGR Vacuum Regulator solenoid should be open. Reconnected the plug to the EGR Vacuum Regulator solenoid and pulled the green vacuum line off the EGR valve, put my finger over the end and could feel a very slight pulsation.. no vacuum however. I lightly tapped the EGR Vacuum regulator solenoid with no change. Reconnected. Disconnected the white / green vacuum line combo at the bottom of the EGR Vacuum Regulator solenoid. The white line had a solid vacuum on it. Reconnected. If I understand the diagrams correctly, the EGR Vacuum Regulator solenoid should be open with 12vdc applied to the connector. This in turn should apply a vacuum to the green vacuum like going to the EGR valve.. resulting in the EGR valve opening. Do I have a bad EGR Vacuum Regulator solenoid or should I move on to the Differential Pressure Feedback EGR sensor? Thanks in advance. Jason j...@citx.com wrote: > Greetings, > [quoted text clipped - 32 lines] > > Jason The regulator solenoid is the last item in line to control the EGR valve, correct? It is ECM controlled. The ECM will ground one wire of the solenoid in pulsewidth modulated fashion when it wants to operate the EGR valve. You don't expect there to be power AND ground at that solenoid at idle in park, do you? The resulting constant EGR operation would make the engine stumble, which would be bad for everyday idle quality and emissions. Apply power and ground to the solenoid manually and see if it allows vacuum through. If this is OK I would suspect the DPFE. You should find testing procedures for it in a Ford manual and/or discussions about it online. If it has stuck or failed internally, it will register the wrong pressure (in the form of a 0-5 volt reading) to the ECM, and can cause inadequate or excessive EGR flow codes depending on how it fails. The voltage of a DPFE is low when there is no EGR operation and increases with EGR flow. One more thing... normally 4.6s clog exaust and intake feed passages, but I don't know how the intakes and crossover tubes are set up on the F150 version of the 4.6. They may be different. At any rate, you said the engine stumbles pretty hard with manual EGR activation. This is a good sign, but doesn't eliminate the possibility that the passages are partially restricted or that several individual cylinder runners aren't totally blocked. Toyota MDT in MO Thank you very much for the response and the clarification! I may just connect my o'scope just to see what you're referring to. It's easy to throw money at the problem.. I just like working on cars. =) Best regards, Jason I have the same code on my 99 Taurus 3.0 DOHC, 66K miles. Valve a bit grungy but working. Passages appear to be OK. Sounds like you are on the right track. I believe the Taurus system is similar; I was going to put a tee in the vac line to a vac gauge and drive it to see what I get. Sending 12V to the solenoid sounds easier quicker, and safer. Then verify correct 12V/ground coming in to solenoid. Let us know what you find. --Don Byrer Don Byrer Instrument Pilot Commercial/CFI Student Electronics Technician, RADAR/Data/Comm @ CLE Amateur Radio KJ5KB "I have slipped the surly bonds of earth; now if I can just land without bending the gear..." Lots of problems with dpfe sensor on a lot of Ford products in the 96-99 at least, range. >I have the same code on my 99 Taurus 3.0 DOHC, 66K miles. > [quoted text clipped - 16 lines] > "I have slipped the surly bonds of earth; now if I can just land without > bending the gear..." Thanks for the great suggestions. I'm going to invest in some elbow grease before some $ on the dpfe. I'm going to pull the throttle body, inspect, and clean the EGR ports/assembly. I would imagine after 175,000 miles it could use a good de-gunk. I'll keep y'all posted. Jason > Lots of problems with dpfe sensor on a lot of Ford products in the 96-99 at > least, range. [quoted text clipped - 9 lines] > > > > Let us know what you find. Last night I pulled the air cleaner & intake off the throttle body (TB). I wedged the throttle open so I could see beyond the throttle plate. Using a spring loaded inspection mirror, I was able to see down the throat and inspect the egr ports on the inside front wall of the TB. Guess what I saw? Well, if you've ever seen those "black snake" pellets you can light and they grow into snakes.. thats exactly what the EGR ports looked like. Both of them had black carbonized muck protruding about a 1/4 of an inch. I decided to remove the TB. =) Sure enough, the ports are plugged and plugged horribly. Once I figure out what the ideal brushes/etc I can use along with TB cleaner, I should have this thing back in working order. The entire removal process for the TB was about an hour. The throttle body (TB) EGR ports were plugged solid. I was kind of going into this blind since I could not tell the diameter of the ports since they were so clogged. For those considering taking the TB off to perform this, the EGR ports are about the diameter of a pencil. I used a dental pick, a .22 caliber bore brush, and TB cleaner from the auto store. After spending about an hour degunking the ports and the tube which runs between the EGR valve and the ports, I blew it out with compressed air and re-installed it on the intake manifold. Incidentally, the tube which goes from the back of the TB to the pcv valve had a hole in it - almost looks like it was torn from someone making the host clamp too tight. Replaced the rubber hose end. I managed to get all of the sensors, hoses, springs and such back in the right place as it started right up. Cleared the codes and went for a drive. Stopped in several parking lots along the way to shutdown and restart the engine (thats when the EGR codes would get thrown and the MIL illuminated). No MIL.. so I'm keeping my fingers crossed. |
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