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Old 04-24-2014
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HELP!!!Losing power at higher rpm's and hwy speeds

Hello, everyone. Stumped on this one. I have a 95 ranger 4.0. It loses all power sometimes while acceleration fast or at higher rpm's. When it happens it begins to run rough and will not accelerate at all. If I pull over and shut the engine off and restart the engine it will run fine like there is no issue. It doesn't do it all the time but does it at the most inconvenient times like when trying to get out in traffic. Any ideas what could be causing this. I have replaced the fuel pump cleaned the throttle body replaced plugs and wires as well as fuel filter.Any help or ideas would be apprecited. idles at 1000 rpm's

Last edited by Grrayner; 04-25-2014 at 11:55 AM. Reason: updated
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Old 05-06-2014
Evo Evo is offline
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mine does the same my 99 xplorer did it to may be transmission body valve gasket timing chain or torqux coverter body valves an easy fix other two require a lot of time and money
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Old 05-06-2014
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Yes, fuel filter would have been my first change.
Could be intermittent Fuel Pump Relay or computer issue, inside the cab in the passenger kick panel or under glove box is the inertia switch, it has a reset button on the top.
Power for the fuel pump passes thru this switch, so it just has 12volt in and 12volt out.
If you were to connect a test light to a ground and the 12volt out connector, you could watch when computer was turning on and off the fuel pump as you drive.
If light stays off and you start to lose power then you will know either the FP relay or computer is at fault, it could also be a loose ground wire, computer Grounds the FP relay to activate it.

I assume that it "feels like" running out of gas and not a dead ignition system when this happens?
And resetting the computer, key off/key on restores the power?

Cleaning MAF sensor would be a good idea, also check it's connector/wires.
MAF(mass air flow) sensor tells computer how much air is coming into the engine, this is the main sensor the computer uses to set the fuel/air mix.

How it works is pretty simple, a wire is heated, and the MAF sensor/computer measures the air flow by how fast the wire is cooled off by the air flowing past it.
There is also an IAT(intake air temp) sensor used with the MAF sensor.
4 wire MAF sensor, then IAT is on the upper intake
6 wire MAF sensor, IAT is part of the MAF sensor

The wire needs to be clean for this to work, and you should use MAF cleaner for this, not carb or brake cleaner.
I would expect a dirty MAF sensor to be an issue full time, not intermittent, but...........

I don't think TPS(throttle position sensor) would cause this because I assume you have feathered the gas pedal when the loss of power occurs, so dead spot on TPS wouldn't cause this.

I assume the CEL(check engine light) works but is not on when this power loss happens?
Do you have an EGR system?

As a long shot, loosen the gas cap and see if problem re-occurs.
The EVAP system sucks air from the fuel tank while driving, on some the gas cap is vented so negative pressure can only get to certain point, other systems have a separate vent, but in either if the EVAP solenoid sticks open and vent is closed, negative pressure can build up in the fuel tank and prevent fuel pump from maintaining fuel pressure at higher speed/RPM.

Last edited by RonD; 05-06-2014 at 10:12 AM.
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Old 07-06-2014
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also try a cylinder pressure leak down test

i may be wrong , but your engine symptoms sound like worn out valve springs
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