Ok, I'm completely stumped!

[Gadget X]

I need help! (other than mental) Ok, here's the deal. I have been extremely happy with my explorer... until now. A couple of weeks ago, it started, well, just not running right. Then a couple of days after that it started really running bad! It doesn't idle as smoothly as it used to, and under a load, it misses, hiccups, sputters, loses power, and occasionally "backfires" in the manifold. It also seems like it is using a lot of gas. Also, if I am "easy" on the gas pedal it seems to run pretty much normally, so long as I don't push too hard on the gas pedal. It's just really annoying, and it seems like there should be some simple "fix" for this problem.
So far I have replaced the MAF sensor, plugs, wires, air and fuel filters, and the fuel pressure regulator.
I have checked the IAC valve, EGR valve, checked the fuel pressure (it's 30 PSI at idle), checked the TPS, checked the crankshaft position sensor (CMP?), checked for vacuum leaks, checked the ignition coil, checked for oil in the coolant and for coolant in the oil, checked that the injectors were firing, checked the codes (got only "pass" codes), sprayed some carb cleaner around the intake manifold to check for leaks there (just replaced the intake manifold gaskets 6 months ago).
If anyone has any ideas on what might be the problem with this thing, I would be eternally grateful!! I have been messing with this thing long enough with no changes that I am starting to consider dousing it in gas and throwing a lit match at it! It just really seems like there has to be some sensor or something that I'm overlooking. Is there a chance that the fuel pump is putting out enough pressure (30 PSI at the schrader valve), but not enough volume to keep enough pressure under heavier demand? Any help here would be great, I'm truly approaching my wit's end! Thanks!

 

[elbow2342]

How about a M.A.P SENSOR ? . Have you checked for trouble codes ? ELBOW

 

[Gadget X]

Don't think there is a M.A.P. sensor. That would be air pressure, right? The only one I know of on the first gens is the M.A.F. Where would the M.A.P. sensor be? would that cause the problems I am having? Also, I checked the codes, there were only "pass" codes.

 

[Maniak]

Early 91's have a map sensor. later 92 and later have the MAF sensor. On rigs with the MAP sensor its on the firewall (under the hood) between the air box and the engine.

~Mark

 

[Anime]

What gas have you been running? Even with eveything else perfect, my X started to lose power and developed a knock/buck when hitting the gas. Eventually I figured out it was the cheap walmart/sam's club/murphy usa gas. I stopped using cheap gas and switched to alternating between Chevron and Shell. It took awhile, but it cleaned the injectors and no more issues. I only use Chevron/Shell top tier detergent gas now.

When the original OEM fuel pump started getting noisy, I swapped it out with a whole new assembly, and it actually did bump up the performance a little.

Maybe you have some blockage in the tank? The factory fuel pump assemblies were mild steel, which rusts pretty bad. When I took mine off the top of it was solid rust. The filter sock on the assembly was brown on the bottom from where rust particles (which probably flaked off the assembly) were constantly being sucked against the filter. It might be worth your while to drop the tank and/or put in a new assembly and lock ring/o-ring. I got a stainless steel assembly from Napa.

How's the exhaust? Is there any rotten egg smell or anything to indicate a clogged converter? What muffler is on there? If it's still the factory system it might be rusting apart inside, and time for a replacement.

 

[CountryBoy78]

sounds like you have checked the basics like plugs,wires,fuel pressure,fuel filter,and sensors.

If I were you check your exhaust system it could be a cloged or collapsed cat. Another thing to check out is your O2 sensors there is one in front of the cat and one behind it.
Sounds to me that its a bad O2 sensor they can cause all sorts of problems that sounds like you are having. Good luck and give that EX some hell.:

 

[explorerguy89]

sounds like dfpe to me =o

 

[Gadget X]

Is there a way to check the cats without cutting them out of the exhaust system? I pulled the exhaust behind the second cat (the only one I can get a look in) and ran the engine for a minute. When I looked in the back of it, it was glowing red, and I could see through the "screen" and see the shadow of the hole at the other end. does this mean that the cat is good? On another note, I do notice kind of a sulfur-y smell at the exhaust sometimes, would that indicate a clogged cat? Also, is there a way to check the dpfe?

 

[explorerguy89]

well dfpe is like $15 so you might as well replace it and with cats only way i no is take out o2 sensor before the cats and see how it runs

 

[Gadget X]

Also, I have been running super premium gas in it, and have tried Lucas' injector cleaner and done the seafoam thing. Would a clogged cat make the Ex get really crappy gas mileage?

 

[explorerguy89]

not that i no of it shouldnt

 

[Gadget X]

I think I might run down to the auto parts store in a few and get a new dpfe then. If I take out the O2 sensors, how will that tell me if the cats are clogged? will the "holes" allow enough air to escape to make up for what the cats are blocking or something? Also, the only thing I can come up with for the dpfe sensor is this.

http://shop.advanceautoparts.com/we...-BWD_3488888-P_2268_R|GRPSENSAMS_673814486___

They call it an EGR pressure feedback sensor, is that right? Thanks for the help!

 

[Mirge]

I think I might run down to the auto parts store in a few and get a new dpfe then. If I take out the O2 sensors, how will that tell me if the cats are clogged? will the "holes" allow enough air to escape to make up for what the cats are blocking or something? Also, the only thing I can come up with for the dpfe sensor is this.

http://shop.advanceautoparts.com/we...-BWD_3488888-P_2268_R|GRPSENSAMS_673814486___

They call it an EGR pressure feedback sensor, is that right? Thanks for the help!

That's it, but I didn't spend that much for mine??

Also, grab some new hoses for that as well...

 

[Gadget X]

Wow! If you think the price was steep at Advance, check this out!

http://www.oreillyauto.com/site/c/d...r+pressure+feedback+sensor&forcedVehicle=true

I think somebody's making a killing on these things! Is there a way that I can check/clean this sensor before I spend more money that I don't have to? I'm getting kind of tired of pouring cash into this thing!

 

[elbow2342]

It might be a good thing to run a fuel volume test. I know you said that you had run a fuel pressure test, but fuel pressure and fuel volume are different. You may have good pressure ,but not enough volume of fuel ,due to a plugged up filter in the tank,or a kinked line. .you need to know if the pressure stays the same at all engine speeds and load.good luck ELBOW

 

[explorerguy89]

well o2 sensors yes should let our enough exhaust

 

[Gadget X]

It might be a good thing to run a fuel volume test. I know you said that you had run a fuel pressure test, but fuel pressure and fuel volume are different. You may have good pressure ,but not enough volume of fuel ,due to a plugged up filter in the tank,or a kinked line. .you need to know if the pressure stays the same at all engine speeds and load.good luck ELBOW

How can I check the fuel volume? do I just hook a hose to the fuel rail schrader valve and then start the Ex up? How much fuel should I get per minute, understanding that the engine will use some fuel, but I don't know of a way to keep the pump running without the engine running. Also, how can I check for fuel pressure under a load?
Thanks!

 

[elbow2342]

The way you described, only you dont have to start you engine. just turn the key on and the pump should start..A descent flow is probably around a pint in 15 secs.. But if you are holding a constant 30 psi fuel pressure even when the engine is running crappy at rpms other than idle.. volume is probably not your problem .Elbow

 

[Gadget X]

Just ran the codes again, here's what I came up with this time:
KOEO
111 (Pass)

CM
157 (MAF sensor below minimum voltage)

KOER
111 (Pass)

Keeping in mind that this is with a brand new MAF sensor in this thing! Is there another problem that I need to be looking at? I cleared the codes after I read it last, so the MAF code should be "current". Getting ready to pull the upstream O2 to see if that changes the "bogging down" problem. This thing is like a steering wheel on my crotch, it's driving me nuts!

 

[Anime]

If the cats are clogged, even with the muffler off, it will smell worse than sulfur, like rotten eggs.

Did you try it without the muffler attached? If it runs great with the muffler disconnected, the muffler is clogged up and preventing exhaust flow.