1996 Explorer EGR Valve repair

[Inverhyt]

Hello!

So I've had a longstanding engine warning light stuck on my dash for awhile that will, every so now and then, turn off for a little bit but eventually turn back on again. One of my friends has a spare ODBII reader so I borrowed that from him to check it out.

I believe it read P0401 (Exhaust Gas Recirculation Flow Insufficient), but we just replaced the EGR? The engine runs absolutely fine, purrs like a kitten and ain't going fast anywhere, but will still get me there even with 200k miles.

I have a multimeter and quite a few tools on hand. How can I check if the sensor is faulty or there's some other issue that I'm not seeing?

 

[96eb96]

Nice truck you got! Insufficient EGR will not cause any drive-ability issues. I would say the DPFE sensor is bad, but its good you replaced the EGR because they are likely leaking and causing small vac leaks by that age.

You could use the multimeter, but your best bet would be to download an app called forscan, install it on your laptop PC(its free, a few bucks for the phone version). It works with OBD adapters. Monitor DPFEV parameter. It should be .75-1V at idle (rock solid). As you drive and cruise that number should go up, and not jump around a lot. You could also take off the rubber tubes that connect to the dpfe and suck or pull a vacuum on them(Key on engine off), the voltage will change in proportion to the vacuum.

If you want to use a multimeter you can look up DPFE pinout and check the voltage, you will have to pin the wires. It could be tricky when you drive, so forscan is suggested and good to have for your truck in the future. Forscan has full coverage for our 96, even the GEM, ABS, etc. No guess work.

95% though it is the DPFE sensor, if it is the metal one it don't owe you anything. I suggest a Motorcraft replacement, if you search online they are inexpensive. The new one will be black plastic. the only other thing could be the vac solenoid, but those don't often go bad.

 

[Rhett]

I believe it read P0401 (Exhaust Gas Recirculation Flow Insufficient), but we just replaced the EGR? The engine runs absolutely fine, purrs like a kitten and ain't going fast anywhere, but will still get me there even with 200k miles.

I have a multimeter and quite a few tools on hand. How can I check if the sensor is faulty or there's some other issue that I'm not seeing?

I've seen every EGR part new (new tube, new DPFE, new EGR valve, new solenoid, new vac hoses) and the EGR flow insufficient code remained.

The problem? Carbon buildup where the EGR enters the manifold. It was tough cleaning it out, but there were big chunks of carbon there, requiring a lot of manual cleaning. And make sure the intake manifold side is clear of carbon too -- not just the outside where the EGR connects to it. Anyway hopefully that will save you some $$$ and time as you diagnose it.

 

[Inverhyt]

You could use the multimeter, but your best bet would be to download an app called forscan, install it on your laptop PC(its free, a few bucks for the phone version). It works with OBD adapters. Monitor DPFEV parameter. It should be .75-1V at idle (rock solid). As you drive and cruise that number should go up, and not jump around a lot. You could also take off the rubber tubes that connect to the dpfe and suck or pull a vacuum on them(Key on engine off), the voltage will change in proportion to the vacuum.

The problem? Carbon buildup where the EGR enters the manifold. It was tough cleaning it out, but there were big chunks of carbon there, requiring a lot of manual cleaning. And make sure the intake manifold side is clear of carbon too -- not just the outside where the EGR connects to it. Anyway hopefully that will save you some $$$ and time as you diagnose it.

I'll make sure to check both out. I don't have a lot of cleaning stuff in my house, but I will certainly check if my buddy has anything for carbon. Do you guys have any recommendations as to how to clean a carbon build up like that? Of course, I could just look up youtube, but I wanna hear if there's any method that's worked well for you guys as I'm pretty inexperienced to be completely honest.

 

[96eb96]

On some applications carbon could be a major issue, like pre-96 4.6L engines. In that case you can blow thru the tubes and there will be obstructions. To check if carbon is a problem, attach a vac hose(pump) to the egr port at idle. Draw vacuum. If the engine comes near to stalling, you don't have a carbon issue, because it is allowing EGR flow(creating vacuum leak). If nothing happens, there is a blockage and carbon is the issue. You can also monitor the voltage while you are doing this, it should change smoothly as the valve opens. If there is no effect there is blockage.

 

[Inverhyt]

On some applications carbon could be a major issue, like pre-96 4.6L engines. In that case you can blow thru the tubes and there will be obstructions. To check if carbon is a problem, attach a vac hose(pump) to the egr port at idle. Draw vacuum. If the engine comes near to stalling, you don't have a carbon issue, because it is allowing EGR flow(creating vacuum leak). If nothing happens, there is a blockage and carbon is the issue. You can also monitor the voltage while you are doing this, it should change smoothly as the valve opens. If there is no effect there is blockage.

I don't have a pump to check that unfortunately unless you can use a standard vacuum with an interesting patch job?

 

[Rhett]

I'll make sure to check both out. I don't have a lot of cleaning stuff in my house, but I will certainly check if my buddy has anything for carbon. Do you guys have any recommendations as to how to clean a carbon build up like that? Of course, I could just look up youtube, but I wanna hear if there's any method that's worked well for you guys as I'm pretty inexperienced to be completely honest.

I removed the upper intake manifold and removed all sensors, soaked the manifold in kerosene overnight, then blasted its insides with a pressure washer. This got some, but not all of the carbon. The carbon remained in the EGR orifice where it enters the mani. So I took dental picks and pipe cleaners and manually got it out, picking at it, then blasting, then picking some more Not easy. Do not do the above if you have a plastic intake manifold (you have a 5.0, and I believe they all had metal intake manifolds, at least on our Explorers).

The best way, in my opinion, to clean an aluminum intake manifold is media blasting using a low abrasion media like walnut shells. Most Audi/VW tuning shops, independent mechanics, or dealerships will be familiar with this service, because many Audi/VW cars have had direct injection for years. DI leads to carbon buildup on the backside of the valves on their engine designs, and the de-carbon procedure is common for them.

I would be leery about the youtube vids where they burn out carbon. I just didn't want to do that as I feared the heat would damage the manifold.

 

[Inverhyt]

I removed the upper intake manifold and removed all sensors, soaked the manifold in kerosene overnight, then blasted its insides with a pressure washer. This got some, but not all of the carbon. The carbon remained in the EGR orifice where it enters the mani. So I took dental picks and pipe cleaners and manually got it out, picking at it, then blasting, then picking some more Not easy. Do not do the above if you have a plastic intake manifold (you have a 5.0, and I believe they all had metal intake manifolds, at least on our Explorers).

Alright. I'll check it out and report back in a few days!

 

[SoHK_alumni]

Hmmm, did not know the '96 5.0 used a DPFE sensor. Thought it used a switch bolted to the back of the EGR valve rather than the pressure sensor.

Think lack of vacuum to the egr, a sticking egr or possibly a duff switch would be likely suspects.

 

[96eb96]

Hmmm, did not know the '96 5.0 used a DPFE sensor. Thought it used a switch bolted to the back of the EGR valve rather than the pressure sensor.

Think lack of vacuum to the egr, a sticking egr or possibly a duff switch would be likely suspects.

Yes, my bad, I didn't see his V8. If that is the case it is like the old 5.0Ls, the position sensor goes bad, it is easy to check that with a multimeter. Just take off and check resistance or use the scantool with a hand pump.

I think 97s have DPFE. An AL intake, like Rhett said, is also a candidate to clog up. The old 4.6Ls before they moved to plastic had that problem too. The V6 has plastic, so that is not a problem.

 

[SoHK_alumni]

Actually, the DPFE sensed EGR was a mid year change for the MY97 5.0 so you and find both the earlier position sensed, internally ported EGR and the DPFE sensed external tube from the exhaust manifold EGR from the 1997 model year Expo's.