fish2222

Hey guys, I am new here, but I need some help! I have an 82 GT that has an 86 5.0 HO EFI transplant in it. The car runs good, but it has some issues. I am getting codes 41 and 91. I was told to change O2's, which I did, and that did not help. One thing that is weird is this. The purge canister is hooked directly up to vacuum. I tried to unhook this, and plug it. When I do this, the idle drops a ton and its hard to keep running. I checked the line going back to the tank, and its open, so I know the venting is fine. As soon as I unplug that line, (the line to the purge from the intake) the idle is fine, even though its sucking vacuum like crazy. I checked the fuel pressure tonight, and its running 34 PSI with the vacuum hooked up, and 42 with the vacuum unhooked. Is it possible that I have a vacuum leak somewhere? I have checked all the lines and I cant find anything, but I am not sure where the PCV valve is either. I dont see it in either valve cover so I dont know where else to look. It seems like it should have good fuel pressure, but im not sure about that either. I have read that it should have 39 PSI at idle with the vacuum unhooked. Anyway, any help would be appreciated! Thanks!

vristang

Your pressure should be 39 w/o the vac, so you are a little high. Are you using the factory fuel regulator?

41 is system lean right or no switching
91 is system lean left or no switching

Since you already replaced the O2's check the ground wire for the O2 sensors. It is a single orange wire coming off the wire harness near the salt n pepper shakers (the larger connectors at the back of the upper intake manifold).
The ground should be attached to the firewall with the engine ground strap.

The pcv is located at the back of the lower intake manifold. It is difficult to see, but you should be able to reach your hand back there to find it.
Also, there is a metal mesh screen under the pcv, inside the lower intake. If this screen is plugged up with oil residue it can cause crankcase pressure issues, so it is a good idea to change it along with the pcv.

fish2222

You know, its funny that you say that about that orange wire. There is an orange wire that is cut off right there at those plugs. I thought it was the orange wire that goes to the EGR opening sensor, but someone had rerouted the wire. That could explain a lot of the problem. The wiring diagram I have shows it being a black/light green wire, but this car has the 86 harness, and I think this diagram I have is an 87 version... The ground strap wasnt hooked up either, but I hooked it up the other day... Thanks!

leadfootdriver

Why would you wanna' unhook it? It's for emissions. It also relieves the pressure in the tank that builds when the gas get warm from a hot fuel pump. The fuel cap only alows air into the tank, but not out. The computer burns the fumes in the motor and leans out the injector pulse to compensate for the tank fumes. If your motor runs like crap (lean) it's because you unhooked this. The computer is trying to do what it was programmed to do but can't because the components aren't functioning. I'd leave it alone. You won't get any more power by unhooking it. The only way this or any other emmision sensor isn't functioning is when you have the pedal to the floor; here the computer shuts off everyting, even the A/C, and takes realtime readings from the O2's to make max power.

No.

vristang

that little orange wire has tormented many a Mustang owner

To further complicate your wire color confusion, Ford sometimes changed the wiring harnesses in mid year.
My 90GT has a 91 Harness.
Looking for specific wire color combinations was useless until I figured out which wiring diagram to use.

Good luck dude
jason

fish2222

Actually, I have an 87 harness too, and I dug it out of the box and looked at it. It has the orange wire with the ground bolt loop, so I opened up the harness to see where it went, and it went right to the same plug that the wire in the 86 is cut at. I just got done repairing the wire and running it to the ground strap and making a good ground connection... Hopefully, tomorrow I will have time to start it up and do another KOER test to see if it fixed it. The only other ground wire that I cant seem to find is the power window ground wire. Where the heck is it grounded at? I have found the black/white wire that is suppoed to be the ground, but I cant find where it actually goes. I am having intermittment window issues, and I am betting that is the problem.

fish2222

Wow, this post got buried fast... Very popular forum, to say the least.

Anyway, today I tried the car with the orange ground hooked up, and alas, away went the code 41 and 91. Now, I have a code 42 instead. By the way, does the EEC have a ground that ties directly to it (the case of it), or are all the grounds in the harness that plugs into it?