My experience with troubleshooting
Thread Starter
'96 F150 XLT
Joined: May 2014
Posts: 78
Likes: 4
From: PA
My experience with troubleshooting
I've done some work from my '96 F150 5.8L with California emission
PO401: I don't replace the EGR (exhaust gas recirculation) valve. At about 127,000 miles later I simply removed the original EGR valve and inspect the plenum port. Nothing was clogged. The next step, the EGR valve was not clogged. And the next step I did was insert the ratchet extension inside the exhaust gas port and press the valve inward and press my finger against the vacuum port for about 2 minutes and the ratchet extension did not move which is the EGR valve is good. If it moves within 2 seconds, the EGR valve is no good. I reinstalled the original EGR valve against the (untorn gasket is good) intake plenum and before I tightened the exhaust tube to the EGR valve, I applied never seize on the 14 pitch thread. The most common problem is the DPFE (Differential Pressure Feedback EGR) sensors go bad due to aluminum housing can get hot from time to time causing the sensor to go bad and the performance and gas mileage can be reduced. The DPFE sensor tells the computer how much EGR flow there is so it can adjust the amount of vacuum applied to the EGR valve thereby opening or closing it more/less. I decided to buy DPFE sensor at a salvage yard and installed it. After about 5 miles the CEL disappeared and the problem was resolved. The gas mileage is good like before 127,000 miles and after I replaced the DPFE sensor. The most I got was 22 mpg (front tank only) on the interstate highway with all windows closed while the A/C was on and the tonneau was covered on my short bed. Like around local area my truck was thirsty around 12-14 mpg. And about 16-18 mpg combined city/highway.
Simple and quick way to check the EGR valve:
Note: If the PO401 shows up on OBD2 scanner, there is another way to find out. One of the hoses blowing off the DPFE sensor is due to excessive exhaust back pressure. A restriction in the exhaust can be a problem. Check the cat converter(s) that has melted/crumbled or a muffler(s) that has collapsed internally.
Minor replacement: Front fuel pump (bought brand new from eBay for 34 bucks). At 121,000 miles the original fuel pump won't start the engine immediately (fuel pressure was good) and finally the pump went bad at around 128,000 miles.
Note: My rear fuel tank transferred fuel to other unused front tank. It started doing it at 121,000 miles (just like the front fuel pump won't start my engine immediately) and I still ignore it to this date because Ford said it is not under recall. If both tanks are filled with fuel, I use the front tank first. Then the rear. When the rear fuel goes to the engine, the return fuel returns about 3-4 gallons per 25 miles (on highway without stopping) to the unused front tank. It doesn't reduce the performance and gas mileage. I have to keep my eyes on the fuel gauge so I can prevent the fuel from purging out the front gas cap.
Mysterious random false codes: The onboard dash fuel tank selector switch sent out a wrong "too fast" signal, shutting down fuel flow from the front fuel pump. I described it was a random or intermittent sudden
loss of power and poor performance, and 4 times wouldn't start. The problem went away after I selected the rear fuel tank. I first disconnected the battery terminal, pulled the onboard switch out from the front panel and disassemble the unit. I discovered a black film on one side of both contacts. I sanded down both contacts lightly. I pressed down both contacts and discovered the one spring was not getting enough tension. I expanded the spring to allow the contact seat tightly against the front contacts. I reassembled the unit and installed it back on the panel, and reconnected the battery terminal. I selected the front tank and started the engine and let it idle so the brain box can relearn during a reboot. I drove around for about 30 minutes in the city and 30 minutes on the interstate. The problem has been solved to this date.
Two things why it failed. #1 The cause of the blackened switch is from selecting the switch while the engine is running causes the contact to arc (spark) against the front contacts. #2 A weakened spring on the one contact causes a vibration due to it was not seating tightly or properly against the front contacts cause to arc.
Now the switch is... good.
PO401: I don't replace the EGR (exhaust gas recirculation) valve. At about 127,000 miles later I simply removed the original EGR valve and inspect the plenum port. Nothing was clogged. The next step, the EGR valve was not clogged. And the next step I did was insert the ratchet extension inside the exhaust gas port and press the valve inward and press my finger against the vacuum port for about 2 minutes and the ratchet extension did not move which is the EGR valve is good. If it moves within 2 seconds, the EGR valve is no good. I reinstalled the original EGR valve against the (untorn gasket is good) intake plenum and before I tightened the exhaust tube to the EGR valve, I applied never seize on the 14 pitch thread. The most common problem is the DPFE (Differential Pressure Feedback EGR) sensors go bad due to aluminum housing can get hot from time to time causing the sensor to go bad and the performance and gas mileage can be reduced. The DPFE sensor tells the computer how much EGR flow there is so it can adjust the amount of vacuum applied to the EGR valve thereby opening or closing it more/less. I decided to buy DPFE sensor at a salvage yard and installed it. After about 5 miles the CEL disappeared and the problem was resolved. The gas mileage is good like before 127,000 miles and after I replaced the DPFE sensor. The most I got was 22 mpg (front tank only) on the interstate highway with all windows closed while the A/C was on and the tonneau was covered on my short bed. Like around local area my truck was thirsty around 12-14 mpg. And about 16-18 mpg combined city/highway.
Simple and quick way to check the EGR valve:
Note: If the PO401 shows up on OBD2 scanner, there is another way to find out. One of the hoses blowing off the DPFE sensor is due to excessive exhaust back pressure. A restriction in the exhaust can be a problem. Check the cat converter(s) that has melted/crumbled or a muffler(s) that has collapsed internally.
Minor replacement: Front fuel pump (bought brand new from eBay for 34 bucks). At 121,000 miles the original fuel pump won't start the engine immediately (fuel pressure was good) and finally the pump went bad at around 128,000 miles.
Note: My rear fuel tank transferred fuel to other unused front tank. It started doing it at 121,000 miles (just like the front fuel pump won't start my engine immediately) and I still ignore it to this date because Ford said it is not under recall. If both tanks are filled with fuel, I use the front tank first. Then the rear. When the rear fuel goes to the engine, the return fuel returns about 3-4 gallons per 25 miles (on highway without stopping) to the unused front tank. It doesn't reduce the performance and gas mileage. I have to keep my eyes on the fuel gauge so I can prevent the fuel from purging out the front gas cap.
Mysterious random false codes: The onboard dash fuel tank selector switch sent out a wrong "too fast" signal, shutting down fuel flow from the front fuel pump. I described it was a random or intermittent sudden
loss of power and poor performance, and 4 times wouldn't start. The problem went away after I selected the rear fuel tank. I first disconnected the battery terminal, pulled the onboard switch out from the front panel and disassemble the unit. I discovered a black film on one side of both contacts. I sanded down both contacts lightly. I pressed down both contacts and discovered the one spring was not getting enough tension. I expanded the spring to allow the contact seat tightly against the front contacts. I reassembled the unit and installed it back on the panel, and reconnected the battery terminal. I selected the front tank and started the engine and let it idle so the brain box can relearn during a reboot. I drove around for about 30 minutes in the city and 30 minutes on the interstate. The problem has been solved to this date.
Two things why it failed. #1 The cause of the blackened switch is from selecting the switch while the engine is running causes the contact to arc (spark) against the front contacts. #2 A weakened spring on the one contact causes a vibration due to it was not seating tightly or properly against the front contacts cause to arc.
Now the switch is... good.