Okay, I have googled and searched forums until I am blue in the face and can’t find an answer to this one. Also sorry for the long post, I just wanted to be thorough on what I have done to it. I bought a 1992 ford F-150 as a fixer upper, it has a 5.0L EFI speed density intake, no MAF. It has 4 speed auto, E4OD, transmission. I had to replace both gas tanks complete with fuel pumps and sending units. Replaced all the brake lines and all brake parts front and back including new emergency brake cables. I then took off the upper intake and removed the fuel rail, I cleaned all of the fuel injectors, put on new O-rings and filters, and pressure flushed them while cycling them. I also replaced the fuel pressure regulator during this and put in new plugs and wires. When I put everything back together it would start and run relatively well. I have not driven it yet, just been redoing a lot on it.

I then started on the interior, rebuilt my Dash and put in a new climate control module, cleaned and repaired the instrument cluster, replaced all the fuses and replaced the ignition key switch. While I was working on the dash, I took the top of the engine apart again. I replaced the EGR valve and the EVP sensor on top of it. I replaced the EGR vacuum solenoid and the EGR pipe to the intake, I put on a new PCV valve, a new MAP sensor, and replaced the EVAP solenoid which had been removed by the previous owner. It does not have an air pump or related parts on it. I also replaced the throttle position sensor, put in a new distributor. I rewired both the positive and negative battery cables with new 4-gauge cable and put on a new power steering pump and new vacuum lines.

When I went to start it after the second round of work it would not start and acted like it was not getting fuel, I traced this down to an error on my part, forgot to plug the fuel shut off valve back in after redoing my door hardware. I plugged it in and now the truck will start right up but will immediately start revving up like it is being given full throttle, I verified the throttle is not stuck and it will do this every time I start it up and does not settle out, it will keep speeding up until I shut off the key. I pulled codes and the only two I have are 327, the EVP is out of range and 121 which was the TPS was out of range, I set the TPS to .96 volts using a voltmeter when I installed it. After this code I checked it on the truck and I am getting 5.02 on the reference voltage, my signal wire was showing 1.66 which is to high and was most likely why I was getting the 121 code. I popped the throttle a couple of times and it settled back to .96 volts. The only thing not testing correctly was the signal return wire which I could not get an Ohm reading on, it would always just show zero when this should be just shy of 2 ohms. I did clear codes and run them again and the 121 code did not come back up but the 327 did.

Does anyone have any idea what would cause the engine to just rev to full throttle every time It is started??

 

I would look into the injectors that you overhauled?
I would verify the spray pattern using a test rail and also see to it that none are drizzling
If the TP is okay and the map reading is within spec for your altitude, you need to look at the fuel system closely
Also, if there is unmetered air entering the engine the processor will send fuel
So, check it for a vacuum leak too
When the above happens, usually the engine surges real bad as the processor cuts the fuel as the idle speed approaches 1200 rpm
So, with a bad unmetered air vacuum leak, the engine goes from 600 to 1200 rpm back and forth quickly
Yours has something wrong for the TP code out of self test range
Also, there has not been an adjustable TP sensor that you can set the voltage on since about 1986
Wondering how you set yours without slotting the bolt holes in the TP
Either way yours is in spec at idle, at .98v (spec was around ,8 to 1.3v at idle and 4.5 to 5v at WOT)

 

The engine ran fine after I put it back together the first time and the injectors were rebuilt before that, and I did not break into the fuel system the second time I took it apart, that is why I was not leaning towards it being the injectors. I did slightly slot the hole in the TPS as it was reading above 1 and everything I have read on these trucks indicated they like it below 1, around 9.5 to 9.9 so adjusted that. I am thinking that maybe I damaged the plenum gasket when installing the plenum and many have a leak there. I installed the plenum gasket and the throttle body gasket dry, I usually use copper spray gasket sealer but had seen a lot of posts that it was better to leave them dry. It would not be out of the question for the computer to have issues either, this truck was very neglected before I got it. As I said in my original post I am not getting an Ohm reading on the return wire of my TPS which should have a reading of slightly less than 2 Ohms with the ignition off. I think this goes to pin 46? on my computer so I may have a ground issue somewhere also, It is storming today but will start chasing it down further tomorrow. Thank you for your information.

 

I would assume that the injectors are okay too then
i might have a 92 PCED and see what it says for pin 46 and whether it is the signal return for the TP
I agree, the meter should read slightly over zero ohms. Your battery was disconnected while you were checking the ohms on that wire right?
We used to see weird stuff like the corroded battery cables inducing voltage into the HEGO wire circuit on Broncos and the HEGOs would read 9 volts. CrAZY things like that

 

Battery cables were connected but I have new cable ends and new positive and negative 4-gauge battery cables, at the time I took that reading I later realized I had my negative cable mounted to the block but not the frame yet, I fixed that and will check again on the return wire test.

 

That body ground is important for the processor
There are 2 processor grounds that need to be hooked up
Might be the problem if there are 2 black wires somewhere under the hood that are not hooked up
Usually by the radiator support or by the starter solenoid, and the 2 wires came out of the main loom

 

yes, I have one that comes off my negative terminal and attaches to the passenger fender, then the main negative cable attaches to the block of the motor then to the frame on it's way back to the battery, the frame one was the one I had forgotten. I think the others are all hooked up.

 

Do you still have the original MAP sensor?
What was wrong with it?
Maybe swap it back on and see if the symptoms change.

 

I do still have it, I did not think the MAP sensor could cause it to go to full throttle like that but it is an easy test before I take the plenum off again. Not sure anything was wrong with it, this truck had been badly neglected and I was just replacing all the sensors to cover my bases. I had planned on keeping it as a spare in case the new one failed on me.

 

Well... All of that and it had nothing to do with the plenum or sensors at all. As I said this truck was a mess when I got it, one thing that was wrong after I fixed the fuel injectors was the vacuum lines, for instance someone had removed the EVAP solenoid and plugged the cruise control vacuum line into the port on the throttle body During my repairs, I put a new EVAP solenoid back in place and hooked it up where it was supposed to go on the throttle body and plugged the cruise control into a vacuum port. That was my issue, every time the truck started the cruise control would go all out. After I replace all the gaskets again and reinstalled the plenum it was idling the way it was supposed to. Then I realized I had forgotten to snap the throttle cable back on, I did that, started the truck and it went through the roof again. Pulled the vacuum line on the cruise control and it settled down and started idling again. So now I get to verify everything on the cruise control but that will be a future project once I get it to driving.