3 miles to the gallon

[baddawg]

My explorer is now undrivable. I used the MAF cleaning link on this site and it made no difference. The vehicle is litterally getting 3miles to the gallon...1/4 tank to go 15 miles. Below is the info from the thread I started in the 91-94 stock forum. As the diagnostic at FORD said the MAF and O2 sensors are reading I am officially stumped. There is lots of pressure in the fuel rail....maybe too much? Is there a regulator in the fuel line that if fails (intermittently) and just pumps the fuel to the cylinders?

I recently bought this 91 explorer as a "post divorce/she got everything/I'm broke vehicle. The body is a little rought but mechanically it is in great shape. Here is the problem.

The fuel is burning rich. Quite irradically it can suddenly burn supper rich with a drop in horse power. I didn't want to start guessing sensors but strongly suspect the MAF. I gave up and took it into a FORD dealer as it needs to pass the emissions test here before plating the vehicle. It failed miserably. They worked on it for 3 hours telling me that there were vacuum leaks (that I didn't find), changed the oil twice (to get the gas out of the oil), gapped the new plugs (that I somehow didn't do right). Their extended emission test found the MAF and O2 among others working fine. What ever they did it then passed the emissions test with flying colors. Yeah....... not so quick!!

It in under 25 miles since servicing started getting rich again right up to being as bad as before with people chocking in my rear view mirror. I have noticed that it usually gets bad when running and higher rpms for a few minutes. If I back the rpms off for a while it starts to run better and the HP returns. Drive it harder and it eventually goes back to killing the local insect population. The clean oil now smells of gasoline again.

I called the previous owner up. He tells me that when it runs rough he used to stop, shut it off, and tap the MAF and it would run better. For the most part he is right.

Here is my question..... Keep in mind that the FORD dealer managed to get some pretty clean numbers only 25 miles previously.

Has anybody heard of a MAF that intermittantly malfunctions?

 

[MrShorty]

It is possible for the MAF to intermittently malfunction. Do you get any codes from the computer? You say it has plenty of pressure. What is the fuel pressure? Is there any gasoline in the vacuum line to the fuel pressure regulator?

 

[IAmTodd]

Fuel Pressure Regulator possibly?

 

[Tony H]

I'm thinking Fuel pressure regulator too.
When they go bad they can run Rich.
I just went through this on a friends Volvo.
P.S. I know more about Volvo's Then Fords but the principle is the same

 

[roob76]

91 x with fuel smell in the oil? i'd do a compression test. i'm not 100% sure but i think if the compression is off bad then it may affect vacuum also which may be why the dealer told you there was a vacuum leak. just a hunch! the dealer probably poured in a can or two of engine restore which worked for the moment like you said. if it's not that you probably should do a compression test anyways being that the vehichle is pretty old.

 

[baddawg]

Today she died.....check engine light.......small backfire on restart try. Checked the vacuum lines. Full of gas. Changed the pressure sensor, oil and filter, cleaned the plugs up and disconnected the battery so computer would reset (over 2 hours). On startup had a bit of nasty cloud but now it feels like there could be some engine damage from the backfire. It idles nice and the smoke is gone but now it feels like a cylinder is misfiring or the timing is off when accelerating and then the check engine light comes on.

The dealer claims to have sealed up some leaks but there just isn't that many vacuum lines on a 91. They said the MAF and O2 were reading. My black smoke issue appears to be gone. So now I doubt the MAF....or should I? It's idling nicely but now feels like the timing is off. Also when I changed the oil I had a few pieces of what looks like a heavy brown paper like crap in my oil...any ideas?

What do you think now?

 

[gtrz]

gasket material?

 

[JDraper]

If you have fuel in the vacuum lines, it is most likely the fuel pressure regulator gone bad. When the diaphragm in the fpr breaks, it allows fuel into the vacuum lines, which causes it to run waaayyy rich.

Have you looked into this yet or is that what you called the pressure sensor in your last post? There is a difference between a pressure sensor and a fuel pressure regulator.

 

[Texan01]

Check the intake manifold gaskets, Fords choice of gasket materials was rather poor and they are kind of prone to corroding away. I did head gaskets on my 95 X and found the original intake gaskets were just about shot due to galvanic (like a battery) reaction, cast iron head, steel gasket, aluminim intake.

you can check the intake gaskets by letting it run and then spraying some wd40/carb cleaner/water......Nevermind, you can't do that without pulling the valve covers which is a major pain in the neck.

I would also pull the codes again and see what the computer thinks, as it could point you in the direction to go. it might think it's running too lean now and richening up the injectors, I'd also run a compression check to make sure no pushrods got bent, that everything was sealing in the hole satisfactory.

I've had a few backfires, but never any serious damage. I've blown up mufflers(kind of funny and a big pow!), and bent a pushrod or 2(not so funny and a medium pow) but only on my Chevy.

 

[94Blue302GT]

Just go and change the FPR.
Maybe even get a BBK or something nice to throw on there. There should NOT be ANY fuel in your vaccuum lines. I'm guessing it took a dump and just let the fuel go right on through with as much pressure as your stock pump could dish out, thus your pressure problem as well.
SWITCH IT ALREADY and let us know if it worked.
it's on the fuel rail, a big metal thing with a vaccuum line going to it straight off of the intake (at least mine is.) Check it out, replace, even with a junk yarder off of whatever. just make sure you use new O-rings on it and maybe even make a little rubber (not cheap paper material) gasket cuz they seem to tend to leak.

 

[MazdaGreg]

Just to add to that, Try to avoid driving it as much as possible when it's running that rich. You will melt down the Cat very quickly.

Just as a side note. Had the Fuel Pressure Regulator go out on my 93, and it runs like GARBAGE when it's in that full rich condition. Not to mention it makes the cat glow cherry red.

Good Luck,

 

[baddawg]

I changed the fuel pressure regulator. It was the rich fuel problem for sure. I ran it all yesterday and it felt like the timing was off or a cylinder isn't quite up to par.

It idles nicely. 1k to 2200k rpm its off a fair bit. 2200 - 2800 rpm it feels a little less off. 2800 rpm and up, lots of power but it sounds very throaty like it had a carb.

I will investigate the intake manifold gasket possibility as that cardboard crap in my oil and the backfire I think are related. I will also pull the plugs today to see if one cylinder is off from the others. I put new plugs in it last seek but they were majorly carboned and then fuel coated. I was told to change the plugs again.....cleaning them and reusing them isn't a good idea? I will look for some codes later today as well.

 

[IAmTodd]

Plugs might be in bad shape from running rich. Change those out as well.