Mustang Has No Power

My '94 Mustang GT 5.0L 5 speed has no power. Well, maybe 100 horsepower. It shows flashes of normal horsepower, but only briefly, after a hot soak in hot (100-degree-plus) weather. After a minute or
so, it returns to its "normal," which is an extreme lack of power and unwillingness to rev over 3800 RPM.
Here is the deal: 160,000 miles on the original engine. Good compression, clean looking (tan) plugs, no excessive oil consumption, normal (mid teens) city gas mileage. Engine is dead stock. No internal or bolt on mods. TPS voltage appears normal, as does fuel pressure (39 psi).
New Parts: Fuel filter, fuel pump and screen, High-flow catalytic H-pipe, O2 sensors, EGR valve, computer, plug wires, cap, rotor, 195-degree thermostat.
Codes: Consistent "EGR lean" codes (171 and 176), no other codes.
Any body with some wisdom on this? We are baffled.
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The fuel pressure needs to be measured when the concern is present... in your case, that means while you are driving. Checking it at idle in the driveway is a lost cause and merely indicates that the pump can supply enough fuel to idle the engine.
HTH.

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i have a fuel pressure guage that just mounts right on the shrader valve that is on the fuel rail. how do i go about getting that to a place where i can see it while i'm driving?
Jim Warman wrote:

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sorry the codes were that the o2 sensors read lean and the codes were 172 and 176
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Has the fuel pressure been read when the concern is happening?

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Does it start good and run okay till it warms up?
Start by cleaning the MAF. Oh wait.. too late to 'start' there.
do a google search on how to..

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i've had a mechanic family friend run his diagnostic computer on it and it said that the MAF was working well Backyard Mechanic wrote:

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Was this the same frient that installed the previous parts ?
Bill
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Then he's a friendly idiot.... unless he checked the Intake Air Temp against ambient air temp, and, even then..
THE POINT IS, the MAF works right but it READS WRONG.
becuase the maf uses a heated temperature sensitive resistor and measures temp by noting the current drawn.
Air passing over it cools the resistor, thus the current drawn relates to amount and temp of the air or the "AIR MASS"
Now, throw an insulating blanket of dust and oil on it, and guess what!
The OTHER possibility is you are overheating or the ECT sensor is reading wrong
Do what I TELL you dammit!
Next time it acts up, stop and disconnect the MaF harness, then drive it and report back. If it drives better, clean the damn thing.. if it's worse, you have another sensor problem, instead or besides.
And you never did say if there are any OTHER problems starting or running BEFORE the engine gets up to temp.
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all hail the Backyard Mechanic. the MAF was very dirty so i cleaned it and as soon as i put it back in the gremlins were gone and its running perfectly. Thank you so much.
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On 25 Jul 2006 09:02:05 -0700, "Randy"

Would you have or have had a K&N air filter by any chance? This is a common occurance if it is over oiled not to mention it does not filter quites as well as an OEM filter.
Lugnut
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no i have an OEM i think it might be getting old though
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On 25 Jul 2006 19:25:13 -0700, "Randy"
Just wondering. It may be just a normal buildup but, another little item you probably should check is the PCV system. (IIRC, you indicated this is a 5.0L V8) Crankcase vapors can backup into the intake if the system is not working well. The 5.0L engine has a filter under the PCV valve that has a tendency to plug with sludge after a while making it useless. You can get at it by pulling the PCV and grommet and, use needle nosed pliers to pull it out. You'll need a new one. Kind of a bitch to get at but, may be worth the effort. This can also cause seal and gasket leakage.
Lugnut
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where is the PCV?
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On 26 Jul 2006 22:02:28 -0700, "Randy"

Top rear of the block behind the right side of the lower intake. You may have to just feel for it or use a mirror. I suppose there are more inconvenient locations but, I can't think of one off hand.
Lugnut
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Randy wrote:

Saved me also a couple years back. I forget what the dealer gets for this little operation not to mention the time saved.
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Have you tried the highly trained techs, with their analyzers, at your local Ford dealer?
mike

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you can clean the MAF sensor but the don't very often work some times and then don't and then work again. They slowly get dirty. But with a lean code just clean it, it only takes a minute. If you can get a datastream on a code reader that is a very helpful tool. The fuel presure gauge you need would have a hose on it and you can read it while driving. The presure we are concerned about is when it is under load. Maybe try brake torqueing it, not the best but closerthe pressure should go up about 8-10 psi under good load compared to idle. does it have a very high idle, vacuum leak? Exhaust leak? I have once also saw a bad dpfe sensor cause this but that is a little too far. have you checked the ignition timing?

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