88 Bronco, 5.0, AOD

Okay, here's my problem and a not so brief description of what I've done to diagnose/correct it thus far. And yes, I've searched, and I've been to the fordfuelinjection website several times.

I've owned this truck for about 2 years, and the check engine light has always been on (p.o. removed the bulb, I put it back). Code 31 has always been the biggie. I initially changed the EGR valve (it was stuck), then the EVP (the resistance was way jacked up) but that didn't fix it. I then realized that most of my vacuum and/or emission lines were broken, missing, or otherwise inop. So I left it for awhile.

I finally got off my butt, went to the boneyard, and got a new vacuum harness for it (all the hard lines bundled as from the factory). The truck now runs much better. I erased the codes, and started over. Did a KOEO test with my scanner, got a 31 again.

So....I checked the EGR valve (it moves with vaccum applied from a pump).

I checked the resistance reading on the EVP (4400 ohms closed to 330 ohms with 10in vacuum). According to my books, this is in range.

I next tested the voltage at the EVP harness connector (4.6 volts) again, in range.

Then, I checked the resistance between the harness connector at EVP signal to socket 27 on the connector to the EEC PCM (0 ohms) once again, exactly what it should be.

I then checked the resistance between the harness connector at EVP signal to ground. I got that the circuit was open. Good, no short to ground.

Next, I checked the harness connector for stray voltage at EVP signal (none found). Good, no short to power.

Now I'm stumped.

I want to clear this KOEO code, so that I can proceed with whatever else may turn up when I do the KOER test. I'm trying to be methodical, sytematic, and not throw parts at it until I know what's wrong. ANY ideas/suggestions would be greatly appreciated.

SOMEBODY SAVE ME!!!

Will

 

Two possibilites I can think of-

1.You didn't properly erase code (doubtful)

2. The Vaccum resorvoir (coffee can) for the EGR and thermactor has hole in it (as mine did) or lines are on wrong. There is a checkvalve in that canister and you must hook up vaccum source to that side- maybe you hooked them up wrong?

Easy way to tell is put a piece of hose on one of the ports and blow into it- if it won't let you- that's the side you hook up the vaccum source from intake/carb -it may even be marked can't remember. Mine was rusted were it bolted to wheel well I didn't find it until i took it off and looked at it.

 

Thanks, I'll check both things, and let you know.