TFP Switch Question

I drive a 99 Mustang...3.8...no mods...just something to get to/from work quickly.

I'm not only on "newbie" level for Mustangs, but for all things mechanical as well, so I'll try to draw from the memory of my conversations with the mechanic as best as I can. Last week while driving to work in the morning, my Service Engine light came on. I had just starting noticing a sluggish acceleration, but decelerating was fine. Later in the day, I started to notice that while cruising at 40 mph, the car seemed to be slightly jumpy as if there was water in the fuel line or as though it was going to stall. After coming to a stop, it idled as if nothing was wrong at all. Oh, and my gas mileage is starting to suck.

With just that explanation alone, the local mechanic determined that I had a faulty spark plug or plug wire. He added that there may be a problem with the TFP switch. Plugs and wires were replaced and I've noticed a definite change in how quickly I leave the stop signs. But, the jumpiness is still there. Does this sound like a TFP switch problem to anyone else or is it too difficult to make that call without having it hooked up for a diagnostic? A friend of mine seemed certain that the oxygen sensor may be behind the problem.

Any/all suggestions are welcome. I hate shelling out the cash without a second (or third, fourth) opinion.

Thanx in advance!

Reply to
<imagegod
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TPS, Throttle Position Sensor lets the computer know the throttle position. These do sound like symptoms related to a failing TPS. I don't have experience with it's position on the V6, but the sensor is on the intake tract near the engine where the throttle cable attaches to the throttle body. It is Black, round with two screw tabs and three wires; Orange Green & Black. Orange is a reference voltage from computer (IIRC 5v), Green is the signal voltage to the computer which is dependant on TPS position ( .5 -

5v), and Black is the signal return to the computer. It can be easily tested if you have an ohm meter by unplugging it and checking the resistance between the Orange and Green wires. Do this with the key off! Initially you should see a high resistance then move the throttle slowly to wide open. The resistance should gradually and smoothly get lower in proportion to the throttle position. If it jumps around and/or has gaps where it goes to 0 (short) or the display looks the same as when test wires are not hooked to anything (open) it's bad and needs replaced.
Reply to
WraithCobra

Mike,

Thanx for the acronym correction and the thorough feedback. After reading your email, I started doing some research online...LOTS of info available and the replacement costs all look the same as what I was quoted by the mechanic ($75 for the part). Also, thanks for putting it in layman's terms. I'm still learning my way around the Mustang's engine.

Tim

Reply to
<imagegod

No problem, that's why we're here. Good luck diagnosing it, and it's very simple to replace. If your test shows that it's bad just ask here how to install the new one. You will only need the correct secure torx bit, a volt meter and are the willingness to say "I did it myself"!

Reply to
WraithCobra

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