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Old 03-30-2010, 11:47 AM   #1
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Default Throttle and bucking

Hey guys,

I have noticed when I give my car 90% throttle, then back off to about 10% then back on to about 40% I get a little bucking. I'm just picking these numbers arbitrarily but if I play with the throttle with this type of load I get this result. What is this attributed to? I have not only noticed it only on my car, but a previous FC RX7, and my stock Saab 9-3. Is this too difficult to diagnose without data logs?

Last edited by dgmorr; 03-30-2010 at 01:32 PM.
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Old 03-30-2010, 12:00 PM   #2
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NVM I fail at reading.

Last edited by Jeff_Ciesielski; 03-30-2010 at 12:33 PM.
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Old 03-30-2010, 12:24 PM   #3
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you mean when you push down the pedal the car speeds up, and when you let off the pedal the car slows down?

try detaching your throttle cable at the throttle body. should fix you right up!
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Old 03-30-2010, 01:30 PM   #4
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Quote:
Originally Posted by fooger03 View Post
you mean when you push down the pedal the car speeds up, and when you let off the pedal the car slows down?

try detaching your throttle cable at the throttle body. should fix you right up!

Is that with the TB butterfly removed while I'm out of the car?

Maybe it is just the engine rocking and gear lash...I don't know. It doesn't feel like it did when it was NA.
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Old 03-30-2010, 06:17 PM   #5
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mine hits pretty hard going from off throttle to part throttle and back - feels like the drivetrain loading and unloading
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Old 04-01-2010, 11:52 PM   #6
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Mine does the same. Not as bad anymore that I am VE tuning. The guys from adaptronic have said it is due to transient throttle. For which I still have not nailed down yet. Are you getting lean tip in? That is most likely the issue.
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Old 04-02-2010, 01:04 AM   #7
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I would say you need some data logs. Probably something to do with your spark map. Example jumping from 25* to 18* in a different cell on your map. I'd look for bumps on your map and try to smooth them out.
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Old 04-05-2010, 04:53 PM   #8
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Quote:
Originally Posted by dgmorr View Post
I have noticed when I give my car 90% throttle, then back off to about 10% then back on to about 40% I get a little bucking.
That is a very common thing to happen if the car is running excessively lean or rich, in that particular area of the map. Try dumping or removing fuel to see what gives the better response.
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Old 04-05-2010, 10:58 PM   #9
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Quote:
Originally Posted by miatamike View Post
I would say you need some data logs. Probably something to do with your spark map. Example jumping from 25* to 18* in a different cell on your map. I'd look for bumps on your map and try to smooth them out.
+1

I was having the same issue until I recalibrated my map sensor. Before the calibration I think I was in timing cells that I shouldn't of been in at.
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Old 04-05-2010, 11:52 PM   #10
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This was fixed with me using acceleration enrichment. It would buck a bit when I would blip the throttle, or let off the gas while shifting gears and getting on it again in the next gear. I was going lean for a second. Now it doesn't do it at all.
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