1994 Exp XLT 4x4 5sp Bad Problems

[deadbird]

Hello,

New to Explorers and this site. Sorry for the long post but I have a big problem. And the worst part is I need every cent for my closing on a house in 2 weeks. This may look long but it is me simply explaining the steps I have already taken to narrow things down so I can more easily be helped. Sorry.

I have a 1994 Explorer XLT 4x4 5 Speed 170k on it. When I first bought it had a check engine light on. It would come on after it warmed up. I never got a chance to check what it was. While driving it I could feel a pulsing when cruising or slightly accelerating. I thought that it was the fuel pump going. As this went on for a month. Then all of the sudden it would feel like it was starving for gas. It would randomly stall and loose power and then regain it right back. I thought for sure that it was a clogged fuel filter or a fuel pump. I continued driving it and bought and replaced the fuel filter. I drove it and it continued to happen. I noticed that this happened only after it warmed up. Like clockwork I could start it let it idol and after a few minutes bam it would start idling bad and eventually stall this would happen the same time as the CEL came on. Sometimes it seemed to be running better when engine light was on. I checked through my list.

Condition: Runs rough and stalls after it is warmed up. This coincides with the Check Engine Light coming on. If I keep driving it will clear up and come back. When it run rough there is black smoke coming out. Seems to run rich.

Fuel filter replaced
Fuel pressure is about 38
Air Filter is good/almost brand new
All Vacuum lines seemed to be intact and connected
PCV Valve good
Oil smelled like there was gas in it
Coolant is oil free
Ignition Timing Good ran the same with spout disconnected
Spark Plugs Replace and Gapped per specs
Checked for spark

I began to suspect the EGR
At this point it is getting hard to drive. When it its Acting up it wont get to 30mph. When it clears up it runs great
I limped it to auto zone only to find out they don’t have OBD1 Readers and I was too stupid to just hop the wire and check it myself. Checked the Pressure sensor and the vacuum controller with a meter. I didn’t know what they should throw but there was a return on them so I figured it was the EGR itself. AutoZone did not have one and it was Sunday so there was no place else.

This morning I had to drive it to work. (6 miles). This time it was the worst it has ever been. Made it there and made it back for lunch. I left it at home after lunch so I could start working in a cold engine when I got home. At this point the engine would stay idling. Took the ERG off with all related parts and checked all connections and hoses and they were good. I sparingly sprayed carb cleaner around and tried to clean the egr. It did not seem to be stuck anymore. While the egr was off. I plugged the hole in the intake and left all other sensors plugged in and started the motor. It ran the exact same if not worse. Unplugged the sensors and it ran the same until it stalled. Cleaned it all up and plugged everything back in and put it back together to see if anything had changed. To my surprise it would not start. I am very meticulous about marking where stuff gets plugged back into. So that is all correct. I even double checked it. I double/triple checked all connections and made sure there were none missing.

Checked spark and fuel pressure again just to make sure and they were fine. I unplugged the battery for long enough to re check the entire engine for connections and even look at a spark plug. It was wet with gas. Hooked the battery backup and tried to crank it. Nothing happened. I have tried every trick I know and even went through the Haynes manual and nothing has worked. The only thing I noticed now as I was sitting in the driver’s seat reading the Haynes manual with KOEO was that the Anti-Theft green light was flashing at me. Don’t know if this is normal or if I may have tripped something. I don’t have the owners manual and there is nothing on it in Haynes. I even gave it a 2 hour break and came back out and tried everything again.

So now I am stuck with a truck that will not start. Does anyone have any ideas? I guess the only good thing is that it seems to turn that darn motor over very well still after a lot of failed starts.

 

[Robrt32]

Clean/replace or check the MAF..... I had almost the same issues and it fixed mine.. Unplug the MAF and see if it runs better

 

[motopsycho650]

Clean/replace or check the MAF..... I had almost the same issues and it fixed mine.. Unplug the MAF and see if it runs better

I agree that a dirty MAF is likely the issue. However, unplugging the Mass Air Flow sensor while the engine is warmed up & running will instantly kill the engine. (I have tried it before)

The MAF is one of the main parts that the computer uses to determine how much fuel to add. The other thing is, the MAF isn't used until the engine reaches a certain temp.

Take off the top of the airbox, and spray out the MAF with carb/throttle body cleaner. make sure to spray out the small hole really well. Give it a little time to dry, and see if the problem improves. If it solves the problem, great. If it improves it, but not fully, you may want to think about a replacement eventually. They are around 200 bucks though...

 

[deadbird]

I will check the MAF tonight. Why would it not be starting now?

 

[motopsycho650]

I will check the MAF tonight. Why would it not be starting now?

I bet that has something to do with the anti-theft light. Does it chank?

I would disconnect the battery for a full 30 minutes or so to clear the computer, and see if it starts then. Mine does not have an anti-theft system, so I don't have experience with that. Most anti-theft systems shut the fuel pump off, or disable the starter relay.

The other possibility for the rough running is a bad/clogged fuel injector. If you can get it to start, put on a glove and pull off spark plug wires one at a time. (wear a good glove or you might get a shock) Each time, the engine should run worse. If you pull a wire and the rough running doesn't change, you have a dead cylinder. Make sure the spark plug is firing on that cylinder, and if it is, you likely have a bad injector on that cylinder.

I had that problem happen on my '92. I went to a junk yard and bought all 6 injectors out out of an explorer for 50 bucks. I cleaned them up really good, and it fixed it. You'll need an upper and lower plentum gasket, and 12 new o-ring for the injectors if you have to tear into this.

Now that I think about it, the intake gaskets themselves can go bad and cause running issues. With it idling, spray carb cleaner or starting fluid around the base of the plentum and around the base of the fuel rail. If the rough running clears up for a minute, you have a bad intake gasket.

All 3 of those problems, the MAF, an injector, or the intake gaskets could throw a code. I'd think they would all throw a lean oxygen sensor code.

 

[MrShorty]

Usually first step, especially when the CEL comes on like that is to pull codes from the computer. What did you get?

 

[nitro71]

Clear the anti-theft light first then try starting, then pull codes. Here you have a problem and you also have a initial diagnosis, CEL. Pursue that first then start in on the other things. If you need to swap a sensor see if you have a pull n save type junkyard near you where you can get them dirt cheap to try them out. Inexpensive way to do some troubleshooting.

 

[doonze]

I agree that a dirty MAF is likely the issue. However, unplugging the Mass Air Flow sensor while the engine is warmed up & running will instantly kill the engine. (I have tried it before)

Maybe if the computer started the trip with the MAF connected, but I ran mine without a MAF for over a month and it did fine, ran well, just didn't have any umph! Course you'll throw a light from the get go, but ran as smooth as you please.

Maybe 94's had a different PCM? Or if you unplug it before starting the truck it starts out in limp home/fail safe mode.... but if you unplug it while the truck is running, It'll kill it?

I've heard stories about MAF's leaving people stranded, but then there are others like me who have unplugged it and left it unplugged for long periods and did fine. Maybe if you also have another bad sensor the PCM can't go into fail safe?

Also, I paid $32 for my used MAF, and a "refurb" from the parts store was like $79 here....

 

[Robrt32]

I ran mine unplugged for a few days... It ran smooth , IF cleaning it hadn't fixed it, I had no intention of buying one.. I can not look at that light

 

[deadbird]

Well I check the MAF as best I could and it looked fine. My friend came over and checked over everything again. We were baffled. He called a Ford MAster Mechnic and the "book" says due to the gas in the oil, gas on the plugs, and the black coming out of the tail pipe that it is the fuel ressure regulator. does that sound right to you guys? Since it is flooding it out and not letting it start it does make sense. I am also curious about the Anti-Theft. How does this system work? The light flashes as I get in and it sometimes flasshes as the motor is turning. But only with the door open. How do I re-set it?

 

[doonze]

It does sound like other reports I've heard of FPR issues, but you already checked that didn't you, in your OP is said pressure was 38? I thought it would be like in the 60's or something when it went out and started causing problems... I know I've read that somewhere on here...

As for anti-theft...don't have it so I'm sorry to say I can't help....

I'd be interested to see how a bad FPR can cause the problems if the fuel pressure is ok....?

I've never messed with mine, so it might just be something I don't know about.

 

[MrShorty]

When the FPr is the cause of these kind of problems, it is due to a ruptured diaphragm inside the FPR, that allows unmetered fuel into the intake. Pull the vacuum line off the FPr (may have to pressure the fuel system) and see if there's gas in that vacuum line. Gas=bad FPR.

 

[deadbird]

I know that when I was playing with my FPR in my 88 Thunderbird Turbo Coupe if I cranked the fuel pressure up and down to compensate for boost that when it was running no boost it ran similar to this. So the normal fuel pressure is suposed to be in the 60s?

 

[cmluther]

Bad Problems...

Had a similar problem - did the same things you were describing. Got it to run, but poorly - work is only a few minutes away, so not a huge deal. When coming home one day, it was loading up, and eventually I smelled gas. As it wouldn't run, I pulled over (it would idle...) and opened the hood - the intake was awash in gas, and it was running off the back of the intake onto the exhaust!

Long story short, for what ever reason, it appears that virtually ALL the o-rings on the injectors failed simultaneously. Suspect that some of the gas additives required in AZ had not mixed well, and that I got a slug of Ethanol or MTBE that dried the old o-rings and resulted in failure. I had previously replaced the FPR, but really don't think that was the issue. Cleaned up the injectors, replaced the o-rings, and re-installed. Been driving relativley trouble-free for almost a year now - just turned 190,000 miles.

One other item to look at is (silly as it sounds...) is the condition of your battery cables / battery. Reduced voltage does very wierd things on anything electronic controlled. While it may crank, it may not be getting the minimum voltage for the various sensors to report properly to the ECM.

Hope this helps, and good luck!

 

[doonze]

Ahhhh... the FPR is the dohicky that leaks fuel into the vacuum lines!! And I thought all it did was control the fuel pressure. I knew the symptom, but had forgotten what caused it.

Yeah, Deadbird, that's something to look into, I haven't had this problem yet, but it's seems pretty common on these. Let us know what you find!

On a side note, so if it is bad (leaking into the intake through the vacuum lines), your fuel pressure will still be in the 40's like normal?? So it just leaks but otherwise functions normal?

And no, from what I understand the normal pressure is like 35-40ish. I have seen people post up that they were getting readings in the 60's and other people posted up that that was way too high...

However, the SOHC 4.0L runs in the 60's normal.... (I've read)

Wow....I read this board WAY too much....

 

[motopsycho650]

Maybe 94's had a different PCM? Or if you unplug it before starting the truck it starts out in limp home/fail safe mode.... but if you unplug it while the truck is running, It'll kill it?
...
Also, I paid $32 for my used MAF, and a "refurb" from the parts store was like $79 here....

I think it's the difference between if it's is warmed up or not. If the MAF is unplugged before you start the engine, it should start and probably continue to run. Because the PCM doesn't see the MAF at all, it never changes to "warmed up" mode, so it will still run.

If the engine is already in "warmed up" mode, it is using the MAF for fuel trim. If you unplug the MAF at this time, the engine dies. I'm not sure if it will restart until it cools back down.

The 200 bucks was an approx OEM price. I don't know for sure. I work in a 4x4 shop, and I'll offer this warning... Aftermarket electronic parts almost always have some kind of problem, and/or are cheap knock-off's of the OEM parts. At our shop, we've had so many return problems because of aftermarket electronics, we install nothing but OEM electronic parts now.

 

[MrShorty]

On a side note, so if it is bad (leaking into the intake through the vacuum lines), your fuel pressure will still be in the 40's like normal?? So it just leaks but otherwise functions normal?

For the most part, yes. I would expect if you did a leakdown test (where you see how quickly the pressure drops after the pump shuts off), you would see excessive leak down as the FPR leaks. Normally, the system should hold pressure for several minutes after the pump shuts off (tolerance is ~1 psi per minute, if memory serves). Of course, there are other possible places for the pressure to bleed off, too, so this isn't diagnostic for the FPR only, but it would indicate the presence of some kind of leak in the fuel system.

 

[mikeinri]

If this were my truck, at this point, I would be taking it to a trusted garage (or preferably dealer if they'll work on it) for an estimate. Pay them whatever they want for the diagnostic, make it perfectly clear that you intend to fix it yourself but need them to point out the problems.

This could save you a lot of time and money in the long run.

Mike

 

[deadbird]

If this were my truck, at this point, I would be taking it to a trusted garage (or preferably dealer if they'll work on it) for an estimate. Pay them whatever they want for the diagnostic, make it perfectly clear that you intend to fix it yourself but need them to point out the problems.

This could save you a lot of time and money in the long run.

Mike

I would but I have no way to move it.

 

[deadbird]

For the most part, yes. I would expect if you did a leakdown test (where you see how quickly the pressure drops after the pump shuts off), you would see excessive leak down as the FPR leaks. Normally, the system should hold pressure for several minutes after the pump shuts off (tolerance is ~1 psi per minute, if memory serves). Of course, there are other possible places for the pressure to bleed off, too, so this isn't diagnostic for the FPR only, but it would indicate the presence of some kind of leak in the fuel system.

I kind of did a leakdown test. I got fed up after checking the pressure for the 3rd time one night and left the guage hooked up and the next afternoon it was still on 15 psi.