I haven't found any info on this problem so I need to throw this out there.
I have 90 F150 5.0, AOD, 4x4. Just finished MAF conversion and installation of Comp cams 250 deg cam. Wiring harness is from PMAS, new A9P computer used MAF sensor/meter from 92 GT, cam is an Xtreme energy 250 in 260 ex 110 lobe sep for the 351/302 H.O. firing order. Firing order on distributor changed to 351/302 H.O. firing order. Other mods include shorty headers, MSD 6A box with Blaster coil. Before conversion and cam install, ran fine, no codes. had MSD box, coil and headers on. After install, runs like crap when I can get it going, a little warm up and will smooth out some for about 2 minutes then shut down. Ran codes and this is what I have;
51-ECT sensor signal is greater than the self test maximum of 4.6 volts
22-MAP/BP sensor out of self test range 1.4 to 1.6 volts
53-TPS circut has intermittantly failed above 4.5 volts
54-ACT sensor signal is greater than the self test maximum of 4.6 volts
35-PFE or EVP circut has intermittantly failed above the maximum limit of 4.81 volts
85-Canister purge Solenoid circut failure

I may be one tooth off on the distributor and am going to try one tooth each way to see if it fixes it, but I doubt it, I don't see where a timing problem will cause these codes, but I'm new to a fuel injected conversions like this.
I have tried to contact PMAS but haven't been able to talk to anybody yet.
Can all these sensors be bad or is there a cause due to something not assembled/wired right?

 

Distributor was not off a tooth so never mind on that. When it runs it is smooth, doesn't want to idle and when it does it wanders. Seems to have good throttle response, and was able to get a rough time on it of 10 deg.

 

I wish I knew...im getting ready to do this conversion so im very interested in your findings.

 

Sounds like a problem with the Signal Return circuit. Test continuity between each of those sensors and pin 46 on the ECU plug, then from pin 46 to ground. Also make sure the ground wire from the computer is secure and has a solid connection (check resistance to battery -).

 

Ok here is an update. My computer was a reman from autozone so I took it back and swapped for another. After doing that I only had a code 22 and 85 but still won't idle. Tested the map sensor (code 22) and it came up bad. Purchased a BP sensor for a 92 GT mustang and code 22 is fixed. Code 85 is the Canister Purge circut off of Pin31. My truck has no Canister Purge solenoid and apparently never did. I am doing a little more research on the wiring diagrams for the mustang to see how the solenoid is wired in caompared to the truck circut. Have a solenoid in route and will create the circut. Although this probably won't make a difference in the way it runs I am moving back to Colorado where every vehicle goes on a sniffer so I want it right. The way the truck was idling it almost acted like a vacuum leak at the manifold. I did prep the upper an lower manifold interface with a surface prep pad on a die grinder. I put a new gasket on and sealed it better this time with good old permatex copper. I am letting it set for a solid 24 hours before starting it up again. I did get in touch with PMAS and they said out of about 40 harnesses they have sold to this point I am the only one experiencing problems...lucky me. They would like to know how things pan out so they can provide feed back to future customers. They are hard to get in touch with but friendly when you do.
I will also recheck all grounds and the rest of the vacuum lines.

 

Wow i have never read about anyone having these problems. Is this what i should expect when i get the kit from FMS?

 

If you take your time and install it properly (as per instructions), you should be good to go.

 

Ok i hope so...i dont want to **** a brick after i do this lol !!!!! mostly sounds like he peiced it togeather and some sensors are failing but thats just me...i know crap about EFI...

 

Another update.
I have found with my truck I have an odd ball application that doesn't jive with many diagrams. With my old computer I had a purple wire in the Pin 43 location. According to PMAS instructions there isn't supposed to be a wire there. I did some digging in Haynes and Chiltons manuals and found that the wire is only supposed to be on 5.8L applications and is an AC circut control wire. My truck is a 5.0 application and always has been, even according to the VIN. Well since there was nothing in the instructions about relocation of any wire from the Pin 43 location and that had to be occupied by a wire in the new harness I left it unattached. I kept blowing AC fuses. If you have the purple wire in the 43 location on your truck computer you must relocate it to the mustang equivelent at pin 54. My AC works fine now. My truck also has no Canister Purge circut. All manuals show that the truck does. I split my harness to track my wire from the Pin 31 location thinking it would come to a cut where a previous owner decided to remove the solenoid. Well that is not the case, it splices into another two black wires that have nothing to do with the diagramed circut. Again this is contrary to PMAS instructions and many wiring diagrams but is obviously factory created. Remember I ran codes on my truck computer and got a system pass code. The truck never had a canister purge circut even though ther is the appropriate gray and yellow wire going to the Pin 31 location. I now have a solenoid and will wire it in according to the appropriate mustang wiring diagram. I have a feeling it will eliminate my code 85. As for the idle problem, I had to slightly straighten the rod connecting the butterfly actuator on the trottle body and the actual throttle cable assembly. I thought that this might mean my TPS is bad but it tests out just fine. My lines from my evap canister run straight to my throttle body and therefor are open all the time sending unmetered air in as if there were a vacuum leak. Once the solenoid is in my idle should be fine and I will readjust my connector link. Again the old computer was wired this way and gave a system pass code, this is the way it was built from the factory and isn't referenced by manuals. I have done tons of automotive work and have frequently come across odd ball problems, especially when doing conversions, and especially in american made vehicles. I am meticulous especially when it comes to instructions, if I wasn't I would not have been able to research and diagnose these circut problems the manufacturer of the commercial harness had no idea about. I will let PMAS know about these two obscure differences and the references I found them in so they can verify them and update their instructions if they see fit.