88 F150 Strange Noise
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Joined: Feb 2001
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88 F150 Strange Noise
In an attempt to fix my 300's stalling problem at cruising speed, I have encontered a strange sound coming from the driver side engine bay or maybe behind the dash on drivers side. It sounds like a "poof" or "pffft". It will make this sound and then the engine will "stall"(loose power) and It only lasts for a second,if even that, and It happens reqularly like every 10 seconds ( I haven't timed it yet though), and you can barely notice the power loss.
It used to buck like it is out of gas or something, but the bucking has not happend since I Changed plugs, plug wires, coil, distrubuter cap, rotor, air filter, fuel filter, and last but not least the fuel pressure regulator. I have checked for vacum leaks. Any help or direction would be greatly appreciated.
It used to buck like it is out of gas or something, but the bucking has not happend since I Changed plugs, plug wires, coil, distrubuter cap, rotor, air filter, fuel filter, and last but not least the fuel pressure regulator. I have checked for vacum leaks. Any help or direction would be greatly appreciated.
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Joined: Mar 2001
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88 F150 Strange Noise
My first thought was that the engine was knocking - try a better grade of gas or check the timing. My next thought is that the sound is coming from the bypass / diverter valve. You should check the appearance of the valve(s) assembly. They should be on the passenger's side near the fire wall. You may hava a faulty check valve or problem when the diverter valve dumps or changes the flow of air from the head to the converter. This is just an idea - I'm not sure how the thermactor system plumbs on an '88. - Sounds like emission system problem.
Elder User
Joined: Apr 2001
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From: Glen Burnie Maryland
88 F150 Strange Noise
Almost sounds like a vacuum leak or cycling in the power brake booster diaphram, from the description of the sound and the location.
Easy check. Pull the line off from the booster and seal off the end. If the noise and the power drop cease, it's your booster. If the noise and power loss continue, then its some where else.
May be also a bad grommet where the check valve enters the booster, when high vacuum occurs the grommet, if deteriorated will roll toward the vacuum source and leak, until equalized. it rolls back and then the cycle repeats. It's hard to find and sometimes see. Squirt some wd-40 around it and check for change in idle. You may also see the WD-40 getting sucked in. I've had more than a few of these go bad with older cars.
check operation of your power assist. turn off engine and pump brakes 2-3 time. They SHOULD get progressively harder with pedal moving less as you lose vacuum assist.
Larry
Easy check. Pull the line off from the booster and seal off the end. If the noise and the power drop cease, it's your booster. If the noise and power loss continue, then its some where else.
May be also a bad grommet where the check valve enters the booster, when high vacuum occurs the grommet, if deteriorated will roll toward the vacuum source and leak, until equalized. it rolls back and then the cycle repeats. It's hard to find and sometimes see. Squirt some wd-40 around it and check for change in idle. You may also see the WD-40 getting sucked in. I've had more than a few of these go bad with older cars.
check operation of your power assist. turn off engine and pump brakes 2-3 time. They SHOULD get progressively harder with pedal moving less as you lose vacuum assist.
Larry
