As strange as it sounds, its along the same lines from what a few others have complained about, but unique.. I need some help on this as its my DD, and I am stranded..

My 94 Ext. 4x4 4.0 Auto, is having some serious issues. I bought it last month, was told all the maintenance was done on it, now at 150,000. Anyways, its been quite warm outside, and when I bought the truck the AC was disconnected, and no fan shroud. I put a new one on, sealed and recharged the AC, plugged it in.

Driving along, I would stop somewhere, and it would not fire up. It acted like it was vapor locked. I checked the rail relief valve, and just a puff. So, installed a new fuel pump, got it going.

A couple weeks down the road, same issue.. idling in the parking lot, died. Couldnt get it to start. Acted like it was vapor locked again. Put in a new inertia switch and fuel pump relay, as well as the new shroud. Got it going...

Again it died, but this time cruising along the interstate. Now eah time I did use the AC as its hot as heck out. So I am stuck along the road when 2 hours go by and finally an oil field worker stops.. He looks under the hood as he is curious and wants to help get it going. He touches the air filter box and its hot, while the intake is cool. He unhooks the <acronym title="Mass Air Flow">MAF</acronym> sensor, and the truck finally fires back up and runs. It doesn't run so good, but it runs! I limp it back into town to a friends garage.

I pull apart the fuel filter, the <acronym title="Idle Air Control">IAC</acronym> and all are in good order. I check all the wiring, and it has good dielectric grease on the connectors. I plug in two other <acronym title="Mass Air Flow">MAF</acronym>'s that we scrounged up, and still, wont run while warm. It gets warm (on the "N" of "Normal" on the gauge) and wont run. I unplug the <acronym title="Mass Air Flow">MAF</acronym>, it stumbles but runs, and can be driven around if not heavily throttled..

What in the world is wrong with it? I need this thing to run badly! I have never had a vehicle run with the <acronym title="Mass Air Flow">MAF</acronym> unplugged, but will die when plugged in and temp is warm..... Help?????

 

Check to see if you're missing a vacume cap at the rear of your valve cover, located to the driverside about an inch from the firewall. My Ranger had a similar problem before and I sure was missing one 1/4 inch cap. As a temporary fix to get me off the road I used a cigarette butt inside celafain to keep it from getting sucked into the engine and a twist tie to hold it from blowing out on any backfire... got to the nearest autoparts store and got an entire pack of vacume caps

 

I will definitely check that out first thing in the morning! Interesting... Very interesting! If that turns out to be the case, I will be floored! And this was the same issue you had with yours? That little vaccume cap caused you all this headache?????

I was able to make a 65 mile drive back to the homestead tonight.. WITH THE MAF DISCONNECTED.. And it drove really well! Crazy! Never ever had a vehicle that could do that! It didnt run as good as used to, but well enough. Little smoke, little more under powered, but made it home solid!

It was mentioned elsewhere that the ECU may be the issue, especially letting an engine run without the MAF.. I had been wondering as well. I want to check out the vaccume cap, then lines first before checking into a new ECU.

 

Combustion is a precision mix of air and fumes, I'd have never thought that this little bit of extra air would have caused it but it did. Better discription of this cap is two inches to the left and two inches down from your wiper motor. OR follow the 1/2 inch line from your master cylender to the left a foot. its a multi port with seven vacume connections.

 

For my sanity, I am hoping that will be it, LOL! I am off to go check it out!

 

UPDATE:

I got out there today, checked around the vacuum tree off the intake manifold on the drivers side. I pulled each connection, checked for leaks, sealing, and reinstalled them. Everything appeared "fair", so I am going to go ahead and replace all the vacuum lines to be sure.

Here is what I found very interesting.. Following along is sketchy, but I will try..

I started looking at the vacuum line that runs from the manifold, to the fuel pressure regulator, there is a "T" and from there it goes to the AC, then to the Air Box, through a button, then to the Hot Air Exchanger on the intake ducting.

I got to thinking about the symptoms from the past and to the current. I bought the truck, and when I did, there was no fan shroud on it, and the AC connector to the compressor was unplugged. I didnt start having issues until it got hot outside, and I was using the AC after I plugged it back in.

I bought a fan shroud last week and installed it, with concern the fact that the intake manifold was scorching hot. After installing it, the manifold could be touched after running all day.

As I looked around, I wondered, since its been hot outside, and the problem happened while on the road with the AC on, I was curious how it may play into the vacuum concern. I know the MAF was unplugged and was running when I had to limp it home.

Here is what I am curious about.. Did the MAF get so hot that the readings to the ECM were off the chart, so by having it unplugged, the lack of readings may have been just enough to operate. This combined with the fact that in the past it seemed there were fuel issues as the rail relief would put out steam and not fuel when it got hot. I put in a new Fuel Pump, Fuel Relay, Inertia Switch, Fuel Screen, Re-dielectric greased all connectors, Fuel Filter, and no change when it was hot out.

With the fuel issue in the past and how hot it got yesterday, I wondered why it did that to begin with. Why did it still seem like it was vapor locking?

Realizing all of this, I now knew that the vacuum lines ran from the intake to the fuel pressure regulator to the AC to the air box.. I cant put my thumb on it, but I think there is something there to check into.

Now, what I did do, was know that it acted vapor locked or air starved, I checked the air box again. There is another vacuum line that runs off the air box, to a heat exchanger on the air ducting. The duct lets hot air in from a tube from the exhaust manifold. I pressure checked the line. Had some resistance issues, and the line was very spongy. I went ahead and pulled the entire air duct with valve body, including the vacuum line.

I went ahead and plugged the MAF back in, cleared the KAM, and restarted the truck.. Fired right up. I let it get to operating temp, turned the AC on to full blast, and let it idle for 30 minutes. After letting it idle, I drove it like I stole it, with the AC going the whole time. I was gone for almost an hour. I went up the mountain roads, around some trails, went in reverse for a while, stopped, idled, shut it off, fired back up, drove it like I stole it some more, kept it at 3000rpm for a bit, brought it back, parked and let it idle with the AC going, ate lunch, went back out 45 minutes later, and still running at 800rpms....

There is some kind of connection between the vaccume lines, the MAF and the hot air exchanger... I am still going to road test the heck out of it, replace all the vacuum lines, and go from there.. Ideas or Input?

Rangerlvr.. You may be onto something...

 

Where you wrote "There is another vacuum line that runs off the air box, to a heat exchanger on the air ducting. The duct lets hot air in from a tube from the exhaust manifold. I pressure checked the line. Had some resistance issues, and the line was very spongy. I went ahead and pulled the entire air duct with valve body, including the vacuum line", you said the resistance issue ??? Did this truck set without some AC line for a while or an open vacume ? Your resistance could be from a pesky Bee (mud dobber). If you squose the line to find its sponginess you may have broke this mud ball up, thus air can now flow as it should.

PS. Your "hot idle" is at 7-800rpm ? GOOD!! Your cold start should be about 1200 for a few seconds. Finally, (of course I now have 1/4million miles on my motor) you may want to step up to a heavier oil to avoid chatter I'm using 40wght now and midgrade gas, if I don't it sounds like someones teeth.

Love the truck, just wish they would stop using plastic parts everywhere. Idler pulley ????? I mean come on, that thing runs constant and even WARM metal barrings will melt plastic. Tranny gearshift housing ????? Come on, I've seen bike tires with better tube rubber than that. I lost alll my tranny fluid once because of it leaking there... locked me up at 70MPH like I hit a brick wall. Solved that problem with an industrial tube from a tractor, Three torx screws from the cover plate off, replaced the rubber and screwed it back on... it's now tighter than fish P**** and nothing is comming out. "Henry" would roll over if he knew they were scrimping on parts to save a buck.

 

You may have more than one problem.
Do you have a CEL lit???? If so, scan the computer for trouble codes & post All code Numbers, as they can offer up good trouble shooting clues. If you don't have an OBD-1 code reader, there are instructions in the "Tech Info" thread, atop this forums thread listing page, on how to do it with a jumper lead, test light, multimeter, or the vehicles CEL light, as they blink the code numbers.

Check the intake air tube duct hot air blend door vacuum motor, to make sure it's working & will hold vacuum, the vacuum lines to it are in good condition & fit tight & that the blend door Fully closes when the engine is warmed up, so it's inhaling cold air, not hot air off the exhaust manafold. If the blend door is stuck open, this is likely the reason the air box was so hot after running it on the highway.

You also need to find out Why the fuel is boiling in the fuel rail, so trace the fuel line back to the tank to make sure it's routed properly & all heat shields are in place.

Are you using a good quality top tier fuel, that has it's vapor pressure properly adjusted for your area???? Did you recently fill up at an out of the way place, that doesn't pump much gas, that maybe still had last winters low vapor pressure recipe in the tanks?????

More thoughts for consideration. Keep us posted on your findings.

 

Well.. All went well for a bit, then back to the same problem! Uhg! LOL!

Good news, when I removed the ducting, I noticed it ran better, but also now when it cts up, I am not stranded! As a matter of fact I made a 230 mile trip yesterday in the heat on the interstate, and all went well. Of course I drove with the MAF disconnected, LOL!

PawPaw: I am wondering that as well. When Rangerlvr pointed out the vacuum lines, I started tracing all of that, then went ahead and replaced them all with the high temp silicone ones. I also used clamps at each connection to a port to prevent leaking. But I still wonder what else could be the issue.

As I said before, I had someone mention ECM, and I did take the truck to the autoparts store, and tried to get it scanned. Unfortunately all I got were communication errors. Wouldnt give me the code!

I will ramp up the fuel quality, see what I get there!
I am going to try the PIN test here.. Thank you!

 

If the computers won't talk to each other you have got a blown fuse most likely, somewhere. Check all boxes and inline ones in some wire harnesses

 

I will check the fuses too! I wouldnt be surprised there either if something like that was plausible.. Working with the Powerstrokes, a fuse can make a world of difference!

 

Hey.. that PIN test on this forum, the link doesnt work!

 

Good grief, we can't seem to inspire the Mods, or Admn folks to get our broken Tech Info links up to date.

So look through this posting for a how-to https://www.ford-trucks.com/forums/1...an-eec-iv.html

Edit: If you like illustrations to go along with the words, try this link. http://www.tomco-inc.com/Tech_Tips/ttt6.pdf

Post All of the code numbers found.

 

Thats the good stuff! Thank you big time! This will help out a ton!!

 

Here is what the PIN test resulted... Finally!

Running engine code was the only one given for: 538