I Love this truck but it is driving me mad. Previous post I went way crazy and put plugs, wires, coil, and other 20$ solenoids on the top. New throttle body, just trying to get it to start. Ended up being the PCM board. Capacitors had leaked all over the board. Got a new one from car computer exchange and it cranked right up and idled beautiful. Drove it for a few weeks, it started to stop at 55 mphs. Just stop no lights no nothing, Dead engine. Went round and round with CCE and they reflashed it or send me another one or whatever. Again it started right up and idled great. A week or so after the ilde would drop when sitting and cutoff but start right back up. 6 miles to my house and it died 3 times.

I started spraying ether on the vacuum lines to see if the engine would pick up, now it was a crazy idle up down up down. The first vent solenoid after the throttle body right before the canister down by the battery came unplugged and the idle picked right up. Ran great.So bad solenoid, right I order one and in the meantime just piped the vacumm direct. It died a few times but ran pretty good. Put good/new solenoid on, the idle started to go nuts. Unplugged it, it straighten out. So I pulled it off the canister and it started to run right.

I need to do my homework on what this vacuum runs and what does it do. I am wondering if I can pull all this smog stuff out. Is the canister bad? The coffee can thing? or what ? The PCM board was trashed, but why is the vacuum seeming to make the idle swing and bog it down to die when the idle drops?

 

have you removed the coffee can, and see if it is rusted out, underneath, quite a few post of this happening, and members sourcing, the plastic ones, little bigger than a softball, or making their own, from PVC pipe and end caps.

 

No I have not I will tonight. I am looking to replace almost all of the vacuum lines. I am looking for a kit now.

 

What engine? Straight 6 is a 300/ 4.9L. The 5.4L is a V8 modular motor not available in a F-250 until 1999. Maybe you have a 302/ 5.0L or 351W/ 5.8L?

 

You got me straight 6 4.9L I do not know why I put 5.4. When I got home I poked around and found a broken little pink vacuum line coming off the block circling the engine and hit a valve up front on top Looks like Air pump by the schematic. I wonder if I can just replace them all.

 

Pink appears to be the TAB (thermactor air bypass) valve vacuum hose. You should probably plan on replacing them all. Once you start moving those old brittle nylon hoses around you will most likely break more of them.

 

Just need to find them. I can but really I am wondering if this is my idling like crazy problem Or the driving and stop running problem

 

Not finding them on Rock Auto any suggestions I did find some silicon vacuum hose

 

check for codes, and a majority of vacuum lines are 5/32", I used the rubber hose (15') and keep the plastic color on each end, to keep with diagram, and do one at a time. or here is 2 sources of hose.
Silicone Boost/Vacuum Hose
Paragon Performance: Silicone Vacuum Tube

good wirte-up on 351w, yours will still have sensors, just a little different locations, tells you size, length needed
93 F150 351w vacuum line replacement - Ford Truck Enthusiasts Forums

 

Update:
Truck has been in the shop since. I picked it up Friday and drove it for Pizza. Saturday to the grocery store, washed it Sunday and drove it to work today. Turns out Car computer exchange does not know how to flash a 1994 f250 PCM board. I purchased another one and had the First Landing auto replace it and boom it started working. They also replaced a few vacuum lines and a solenoid and an O2 sensor.

CCE boards I sent back to them 3 times only to get the same one back. This last flash would not fire 4,5,and 6.

For now it seems to run fine. The idle still wants to bump between 4 and 9 grand. if it drops below 4 it will shut off but start right up and drive fine.

 

That's some big revs! lol
Recently, I gave my f150 a freshening up. New plugs, wires, all the usual stuff. I replaced the tcv and some of the vacuum lines while I was at it. Shortly after, it started running sporadically. I was looking everywhere for the cause. Some days it would run well and some the idle would jump all over. Other days it would die at idle. I thought it was a sensor and so I tested them all. Everything checked out. So I decided to check the fuel system. That day the truck ran like total ***. Stalling while driving., sputtering and choking.The next day I replaced the fuel pressure gauge. Fixing the vacuum lines had put more pressure on that old diaphragm and it gave. If your truck is still struggling to hold idle, I'd check that part out. The computer was just trying to keep.up with an irregular fuel pressure.

 

I don’t think you can flash the PCM of an EEC-IV vehicle. That is why the aftermarket tuner companies ( ie Superchips and others) would plug their performance tunes into the port on the rear of the case.

I’m not convinced it is “fine” since the idle wants to run the engine up to and beyond the redline. seems to me you might still have a defective PCM. A few people have had good luck with the Cardone reman computers. I have never heard of the place where you got yours.


Replacing the fuel pressure gauge you or the previous owner added fixed it or are you talking about the fuel pressure regulator on the fuel rail?

 

Sorry, I meant the fuel pressure regulator on the rail. No guage. I replaced the regulator and all the idle issues were fixed. It was getting too much fuel to the injectors.