‘87 F150 5.0 EFI AOD 2WD
CODES 31, 10
Of course, as I was driving to have new tires installed, not one mile out the truck started shaking, sputtering, and misfired while driving. This happened about a week and a half ago, directly following a transmission fluid change that included the torque converter. My fuel pressure was low at 27 psi in idle and it prompted me to go ahead with my plan to replace the rear tank and sending unit, and fuel line while bypassing the selector valve. I was still low on fuel pressure so I did some standard tests on the fuel pressure regulator and found that there was no change when the vacuum was pulled from it and when I pulled it to clean and investigate, I found that the spring couldn’t be persuaded to contract. I went and bought a fairly inexpensive unit (I’m sinking a good bit into this vehicle and need a good solid minute of driving before another big parts splurge) and after replacement I was riding higher at about 30. It helped and it ran great for the last five days and then started doing the exact same thing again 15 minutes ago.
i’ve installed most of the ignition system, alternator, plugs, fuel pumps, homebrew exhaust system and all things listed above. Please, give me some ideas where to go from here.
Thanks to all.

 

On the way home, the problem was continuing and worsening. I’m not sure why, but for some strange troubleshooting reason, I flipped to the front tank selection on the dash, expecting a quick shutdown of the engine, but somehow the problem disappeared, none stalling, none stuttering, none jerking violently. Why would that be weird? I have completely disconnected my front tank. This leads me to believe one of two things are at play. One: they are switched electronically and I’ve been running all this time on a overfilling front tank that has been return filled by the rear tank (where I’ve been putting the gas) and the first experience I had was a final, inevitable emptying of the tank, or Two: the combination of rear tank low pressure pump and hi pressure pump has somehow cavitated sending air to fuel rail? Switching tanks disabled the low pressure pump and it ran better with only the high pressure pump providing fuel. Imma go do some tests to see what is the case.

 

At 17 in Hg vacuum, which is what im getting at the manifold when there are no leaks, Map sensor is sending 2.1V at 108 hrtz
At 12 in Hg vacuum, with a cap pulled off of tree, MAP reading is more reasonable at 138 hrtz

 

Di you bypass the selector valve on the return line too? If not that is your problem.

 

Thank you very much for the repIy. Feeling frustrated and alone in the high grass.
I did, I run straight from the 3/8 fitting on the sending unit of the rear tank to the fuel pump, and straight from the return out of the fuel pressure regulator to the 5/16 fitting on the sending unit of the rear tank.

 

Drove home from work and bout three minutes into the 15 min fife, I felt the truck gasping and starting to sputter, so just to give it a go, I switched to my nonexistent front tank and shifted to OD. I made it home without incident. I did spend quite a bit of time changing hose size and connector sizes on the vacuum tree while reading vacuum levels and MAP frequency trying to get a decent idle. But I’m not sure my haphazard approach is getting me far and I’m having a hard time finding absolute values for vacuum pressure from the manifold to any given component. If anyone could point me in a direction, that would be glorious.

 

31 O/C, 41 C, 82 O
Drove to and from work today and collected these codes, I checked the O2 sensor ground (grey wire?) and got .01 ohms, the black wire showed 39M, which all appears pretty alright. gonna try to register a return voltage while running and make sure it's talking. I'm trying to puzzle out the EVP code. There's a good flowchart diagnostic for code 32 at ALLDATAdiy, I'm looking at my Haynes as well, but I'm just not getting what to do for this one. I really could use some guidance or anyone to help me out. I'm frustrated and angry (not an emotion that I'm used to) and I'm reading as many other forum posts that are similar to mine as I can and the wonderful back and forth from the members helping people like me who are lost. It makes me a little jealous that there was so much support for them. I'm sweating and nervous that I might not make it to work in the morning or home in the evenings. I'd really love to love this truck, it's very close to awesome, but it's making it hard on me. I want to bring it back, but It's quite the challenge. If there's something I'm doing wrong with my posts, please let me know. I'm checking and reporting fuel pressure, vacuum pressure, codes, my info is in my signature, and I'm trying to remember and report repairs and maintenance I've performed. I'm wondering if somehow I've offended y'all in my very brief existence on this site. I'd offer my sincere gratitude to anyone who might take the time to read and reply.

 

41, where is your O2 sensor in your homemade exhaust?
31, take vacuum line off EGR, and plug it and see if it still shakes/stalls
82, Tab does it still have the smog/emissions on it, is what this is.

 

31) O2 is passenger side, between two header pipes upstream from where the plugged cat was before I pulled it. It is a new Bosch
82) the TAB is hooked on the lower nipple to the vacuum res and upper nipple to something I cannot ID behind the engine passenger side as it was when I bought the truck.
31) is this the EGR?

if so, there is no vacuum to it, no change when pulled. The solenoid that the vacuum hose comes from shows 14V on both wires to ground.

Thank you very much for your help.

 

In case anyone might real this....
After I first bought this truck, it stopped starting. Like as soon as I got it home. Turned out to be the entire ignition system. The only thing I farmed out was the distributer module because I was scared to remove the distributor cap et all to get at the TFI so as not to screw up the timing. Well, funny thing. as I was working on the wiring, I kinda bumped the distributor cap and it spun around about 25-30 degrees. I figure it wasn't tightened down very well at the shop, huh, and all these mystery symptoms I've been chasing, well not all, have been the result of the truck performance reacting to advances and retardations of the timing. Sometimes a mix of the two in a single trip. Shoulda caught it sooner I guess, but I thought that was all pretty well sewn up tight. Now to start another thread about the strange things happening to me now that I've "fixed" the timing in this truck. Thanks to the few who gave helping me a stab. Can't thank y'all enough.