Hi all,

Have been lurking around this message board for some time soaking up all the info here (very thankful), and haven't been able to quite find a solution to my problem, so I decided to finally ask for a life line on my issue and make my first thread.

I've got a 1996 F150 shortbed 4x4 with the 5.0. There's something like 180,000 miles on the body/transmission with a swapped engine that supposedly has about 80,000 on it. The problem is the engine is NOT from a 96 - I'm not sure how exactly to tell the year but I think it's from a 94' or 95'. This has already caused a few issues, like clearing the crankshaft sensor error code I was getting. I've been working through one problem after another to get this thing in good running order and have been fairly successful so far for the shade tree mechanic that I am.

In any case it's the throwing the infamous 401 code and I've got pinging under light load when the engine is warm. I suspect something with the EGR or DPFE and in the process decided to replace all my cracked vacuum tubes with rubber. the previous vacuum set up did not look to be factory and some lines weren't connected to anything, others were plugged with screws, and others seemed to just go right back to themselves. I believe I've run almost everything correct as far as the emission stuff goes but I've got one problem left - neither of the vacuum tubes coming off the DPFE are connected to anything. I've tried tracing the tube from the bottom of the EGR down through the plenum but it doesn't seem apparent where these things are supposed to connect on the tube. And as I understand it some tubes don't have any ports for vacuum lines? Is it possible someone put the DPFE in because the truck is OBD-II and will throw a code without it, but the EGR tube is from a different year and doesn't have the ports? Or am I just failing to located the ports without the plenum off? With those vacuum lines from the DPFE not connected to anything(or possibly from me rerunning the new vac lines wrong) the engine stalls and sputters when idling when I connect the vac line to the top of the EGR to the top port of the EGR solenoid, so at least I guess the EGR operates.

Either way I would certainly appreciate some help with this. I'd hate to take the truck somewhere to have all the vacuum lines redone if I'm only a few steps away. Thanks in advance!

 

The two "vacuum" lines that run from the EGR tube to the DPFE sensor are not vacuum lines, they are sampling flow/pressure. On a 1996 5L engine used on a F150/Bronco the computer samples EGR flow via those sample tubes located on the EGR tube. It's a one year only piece and very different from the 1995 and earlier EGR tubes and EGR feedback system. In order to fix the P0401 error code you need the correct EGR tube with the sample ports. The tubing that runs from the EGR tube to the DPFE sensor are silicone, rubber will not work due to the high temperatures.If your EGR valve still has the EGR Valve Position (EVP) sensor on top of it you should install the correct version.

If your engine is stalling when you connect the vacuum line from the EGR Valve Regulator (EVR) to the EGR valve the EVR may be bad. Under idle/no load conditions the EVR is supposed to be closed, which blocks vacuum from getting to the EGR valve. If some of the vacuum is allowed through, the EGR is opening which in effect is a vacuum leak and the reason why the engine is stalling.

 

That makes so much sense and probably explains a lot about what's going on with my truck. I imagine swapping that tube out will not be a fun job. In a similar vein to all this, my vacuum tree seems to have more ports than things to be connected. I wonder, does it matter which port is connected to which valve/vac reserv etc and can some of them be plugged without consequences for the engine? Or is rather that there is a very specific routing in which all the vacuum lines must be connected?

 

also, should it be obvious if I have the correct EGR tube with the sample tubes? I can't seem to find them but I also may looking in the wrong place. my EGR valve does not have the sensor on top, the DPFE is on the other side on the throttle body.

 

Very common to have unused ports on the vacuum tree. Nothing is really position dependent. I would advise to run the PCV vacuum line to the center vacuum tree. This was a technical bulletin issued by Ford years ago. For the unused ports, cap them off.

 

Thank you very much for your response and advice!

 

Very obvious where the sample tubes are located on the EGR tube:



Ford Part Number# F6TZ-9D477-E


On your 5L engine this tube runs from the lower intake manifold to the EGR valve.

 

I see. So in the truck they should be sticking out somewhere below the throttle body?

 

Below the upper intake.

 

got it, thanks again!