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Discussion Starter · #1 ·
So I'm sure there's a simple explanation for this, but I've never really asked. Just like in every other MTX I've driven, it feels like my engine is almost bucking/stuttering when I coast. Why is that?

Example: I accelerate to 25 mph, and I'm in second gear. I see up ahead that traffic is stopped, so I suddenly let off the gas completely without shifting or touching the brake. Immediately the car feels like every once in a while something significantly slows it down...but just for a tenth of a second. Almost as if I keep tapping the brakes. If I give it a little gas, it stops.

This has happened since the first day I owned my car, and as I mentioned above, has happened in every MTX I've ever driven (all Fords). But I still don't understand what's going, and what causes this to happen. Care to educate me? [wrenchin]
 

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maybe it has to do that the transmission is engaged to the engine and your feeling the RPMs slow down and therefore causing bucking?

makes sense to me
 

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Discussion Starter · #3 ·
That makes sense, but why would it come in short bursts?
 

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I noticed this in my svt. Its more noticeable with an aftermarket exhaust, but I think it has to do something with burning extra fuel or somthin like that and it burns and crackles lol, probably a wayyy better more detailed answer then that out there though
 

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Discussion Starter · #6 ·
I noticed this in my svt. Its more noticeable with an aftermarket exhaust, but I think it has to do something with burning extra fuel or somthin like that and it burns and crackles lol, probably a wayyy better more detailed answer then that out there though
That's what I originally thought was happening. I figured because I instantly let off the throttle, the mixture was running rich, thus what felt like "bucking". It's almost like a similar feeling to my MAF sensor being dirty, or the upstream O2 sensor malfunctioning.

The only reason I would second guess myself is that I thought letting up on the throttle made it so that only air was flowing through the engine, and not a mixture that was actually firing. Hmmm.
 

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That's what I originally thought was happening. I figured because I instantly let off the throttle, the mixture was running rich, thus what felt like "bucking". It's almost like a similar feeling to my MAF sensor being dirty, or the upstream O2 sensor malfunctioning.

The only reason I would second guess myself is that I thought letting up on the throttle made it so that only air was flowing through the engine, and not a mixture that was actually firing. Hmmm.


its always flowing a air/fuel mixture, otherwise the engine would die.

How about this, with my clutch pedal all the way down, if i rev the car high enough it will actually creep forward ;) Someone told me to do this at the strip and i was like yeah whatever, and sure enough it did it.


If this is the 2011 were talking about this is highly unlikely, but Usually when your rotors are warped it can have this bucking sensation from the brakes dragging every time it hits the warped part, but it would have to be bad.
 

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Discussion Starter · #8 ·
Yeah, it's definitely not a rotor. It's a random slow-down, and I've driven with warped rotors before. You definitely know if you have a rotor warped enough to hit the pads.

As for the air/fuel mixture, I thought the engine can't stall out if you're moving with the clutch engaged (unless you're going really slowly)? Everything I've read about hypermiling always said that the car uses 0 gas if you coast in gear, but some gas if you disengage the clutch, thereby putting the transmission in neutral.

But hey, I have no clue. That's why I'm asking :)
 
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