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Loss of Power on Hills (NEED HELP!)

phisherman162

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Aloha, OR
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1991 Explorer 4.0
So here is the deal:

91 Ex, 150,000 miles 4.0 Auto

Burns 1/2 a quart of oil per 3000 miles, coolant levels are good, never change. Tranny fluid level good, plugs were fine 6 months ago.

Heading up hill, I have a horrible loss of power. Even when I have my foot all the way in it, it won't go. On flat ground, she runs fine, other than a little hesitation now and again. I wouldn't call it a miss, it just drops the RPM's for a split second. I changed the air filter today and took it out for a test drive. Heading up a fairly steep hill, it started losing power and the temp started climbing. It never got out of the "Normal" range, but it got up in a hurry. About half a mile up the hill, I turned around and headed back home. As soon as I turned downhill, the temp dropped immediately. I have been having intermittent problems with this rig for about a year, but never anything that took it off the road. The Overdrive dropped out about a year and a half ago, but it has ran fine regardless. Torque converter still kicks loose when you take your foot off the gas.

Timing? Sensors? Tranny? Fuel?

Here is what I have replaced:
Fuel Pressure Regulator, 1.5 years ago
Fuel filter, 1 week
Air filter
Changed oil 1 week ago
New exhaust from the header back, 6 months
Radiator, 2.5 years ago
Alternator 2 years ago
New hoses and belts 2.5 years
Tranny filter 2.5 years ago

3 years ago the previous owner put about $4500 into the rig replacing every gasket, fixing every leak and replacing everything that looked worn.

I need to find a list of the different sensors that could cause the problem and how to test them. (both O2, TPS, MAF, Exhaust Gas, etc.) This is my only rig and I am stuck taking the bus 2 1/2 hours 1 way to work every day. Any help would be appreciated.
 



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Verno

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I'm no expert here, but after reading your full post - my guess is it would have to do with your loss of Overdrive. My 94 loses a little bit going up hills, but if I put my foot into her, she will kick down and climb like a monkey to a tree! You may just be losing some HP due to wear on the motor (rings/valve seals, etc) and only notice it under "severe load."
 






Tbars4

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...My guess here would be fuel related...Your fuel pump may be going out...:dunno:

...When you loose the power going up the hill is a common sign of this although, with the information you posted, I wouldn't rule out the tranny...
 






Verno

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...My guess here would be fuel related...Your fuel pump may be going out...:dunno:

...When you loose the power going up the hill is a common sign of this although, with the information you posted, I wouldn't rule out the tranny...
YES, I totally forgot that. Only under heavy loads will you detect a fuel pump that is weakening too! I was looking too much into the OP's litany.
 






Four0Sport

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have you checked everything regarding air/fuel mixture and ignition? any CELs?

I would run down through and check the plugs again, the condition of the wires, the coil pack, the mass air sensor.. and pray its not the transmission.

when you say lost overdrive do you still have all 4 forward gears but lost the torque converter lock up? if so ive been running the same way for 3 years and do not have a loss of power on hills, nothing you describe anyway.. my problem is big tires and high gears.
 






MrShorty

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Fuel problem is a possibility. Start by testing fuel pressure, and you may want to rig something up so you can monitor fuel pressure while driving up the hill to see if fuel delivery keeps up with fuel demand.

IMO, the first step in testing any of the engine management sensors is to pull codes from the computer. Plenty of instructions in the EEC-IV forum.

It never got out of the "Normal" range, but it got up in a hurry. About half a mile up the hill, I turned around and headed back home. As soon as I turned downhill, the temp dropped immediately.
sounds like a dying fan clutch. I can't remember well, but I almost want to say that I had a similar "power loss" when my fan clutch was going out. I think when it started to get too hot, it lost power -- can't remember too well.
 






phisherman162

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The loss of power came before the temp. The temp is a new thing. Only has problems uphill. It does seem to get a bit worse when the rig is warmed up, though.
 






phisherman162

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This isn't just a little loss of power. On the hill home from work, I can take it at 70 in my toyota, 60 in my ex. I crawl up it at 35-45 now.

No CEL.

Fan sounds like it is working fine.

No 4th gear in my tranny. TC kicks out and in just fine, but no 4th.
 






fixxxer

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The TC lockup IS the 4th gear/OD
 












jakeamondo

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Loss of power on hills

I have manual tranny and recently i noticed a slight hesitation when i shifted into 3rd gear. This happened about 5,000 miles after i did upper and lower intake gaskets, fuel injectors cleaned and tested, new spark plugs, water pump, fuel filter, water pump, valve covers etc.

The only thing i didn't replace at the time was the spark plug wires, my parts store didn't have the right ones. I finally decided to replace the wires. The hesitation is gone and i can now make it up my steep hill in 3rd gear. The old wires were only a few years old, but, i had them off a fews times to change the plugs. A miss fire can cause hesitation, loss of power, and increased engine temperature, resulting in oil consumption.
 


















Rolando G

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Fuel problem is a possibility. Start by testing fuel pressure, and you may want to rig something up so you can monitor fuel pressure while driving up the hill to see if fuel delivery keeps up with fuel demand.

IMO, the first step in testing any of the engine management sensors is to pull codes from the computer. Plenty of instructions in the EEC-IV forum.

sounds like a dying fan clutch. I can't remember well, but I almost want to say that I had a similar "power loss" when my fan clutch was going out. I think when it started to get too hot, it lost power -- can't remember too well.
change DPFE sensor clean EGR valve and clean MAP SENSOR
 












1991 sploder

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Yea and no egr in 1991 explorers or dpfe or map really...
 






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