what causes bucking

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Feb 8, 2008 | 08:29 PM

Jrp1978

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what causes bucking

I have horrible buckinng 1200 to 1900 rpm ?

Feb 8, 2008 | 08:30 PM

ONEBADASSWS6

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Vehicle?? Engine??

Is the check engine light on??

When was the last time it was tuned up??

Need a bunch more info.

Feb 8, 2008 | 08:31 PM

ssfast99

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i would say a big cam and or a crappy tune. but more info to pinpoint.

Feb 9, 2008 | 02:20 AM

mikey67

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I had an '88 Beretta years ago that hadn't had GM's speed density upgrade. I had this problem and the maf was bad, no SES. Not the same car but worth checking.

Feb 9, 2008 | 11:58 AM

Jrp1978

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ls6 stg 2.5 heads

trv 3 cam .643 .598 232 234 duration

headers

ud pulley

lid

p p tb

partick g mail order tune

The thing is there are day where is wont do it ?

Feb 9, 2008 | 12:14 PM

Demon Of Dreams

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From: Houston...

it's the nature of your cam and tune... mine does it on colder days but when its a bit more humid out it drives perfectly fine

Feb 9, 2008 | 12:33 PM

ssfast99

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Tune.

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Feb 9, 2008 | 01:30 PM

92slowmaro

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From: above you

put some gears in it. it will make your car perform better and will up your rpms so it wont buck as bad. and get a dialed in tune.

Feb 9, 2008 | 01:30 PM

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3.4camaro

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too much ignition advace and/or too much airflow.

Feb 9, 2008 | 01:55 PM

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Jrp1978

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Its got 410 and a m12 tranny

Is it possible that this throtttle body i have that you can see light all the way around the blade when it is closed is doing this?

Feb 9, 2008 | 02:14 PM

#12

92slowmaro

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well that may or may not be causing the problem. but you should get that fixed. and then have your tune dialed in

Feb 9, 2008 | 07:16 PM

#13

Jrp1978

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hmmmmmmmmm

so what is it timing or fuel? At anytouch of the throttle the timing read 40.4 until wide open and it reads 28.8

Feb 9, 2008 | 07:42 PM

#14

shoemike

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From: Prescott, AZ

Quote:

Originally Posted by Jrp1978

ls6 stg 2.5 heads

trv 3 cam .643 .598 232 234 duration

headers

ud pulley

lid

p p tb

partick g mail order tune

The thing is there are day where is wont do it ?

Feb 9, 2008 | 07:50 PM

#15

edcmat-l1

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From: Va Beach

Quote:

Originally Posted by Jrp1978

so what is it timing or fuel? At anytouch of the throttle the timing read 40.4 until wide open and it reads 28.8

Theres part of your answer right there.
With the bigger cams, reducing the low load low rpm timing helps the bucking a bunch.
Stock, the timing in that range is 41 deg. I start with that range reduced to about 38 degrees, and have run em as low as 34.
You also have to make sure the fueling is close too. If the trims have to adjust a bunch it'll make it worse. You'll always a little bit of low speed surge/buck, but if tuned right it will be real close to stock. You can get a bone stock one to buck and surge if you lug the motor low enough.
Do you have tuning and logging software, or did you send him your PCM?

Feb 9, 2008 | 08:24 PM

#16

Jrp1978

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so i took some timing at 1k to 1800 out and no bucking and now it wants to hang rpms at 1500 and stay there until i stop.

Feb 9, 2008 | 11:03 PM

#17

Demon Of Dreams

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From: Houston...

Quote:

Originally Posted by Jrp1978

so i took some timing at 1k to 1800 out and no bucking and now it wants to hang rpms at 1500 and stay there until i stop.

i still fight with mine sometimes with that... for mine, i'm either running too rich or theres too much air getting in, because it doesn't go away until I'm at a full stop for over a second or two, when it does it

Feb 10, 2008 | 11:12 AM

#18

FoolZRacing

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sometimes when its hanging you can adjust the throttle follower multiplier and decay rate and itll help the hanging idle.

Jan 11, 2009 | 11:43 AM

#19

LS1HIGHLIFE

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From: Williamsburg, VA

Quote:

Originally Posted by Jrp1978

I have horrible buckinng 1200 to 1900 rpm ?

Mine does this also and was told it was in my tune.... I'm having her looked at again real close in a few months to rectify some tuning issues I'm having. I'll post up what the guy finds when I get it done.

Jan 12, 2009 | 07:30 AM

#20

m6speed

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From: Maryville, IL

Quote:

Originally Posted by Jrp1978

ls6 stg 2.5 heads

trv 3 cam .643 .598 232 234 duration

headers

ud pulley

lid

p p tb

partick g mail order tune

The thing is there are day where is wont do it ?

it took a while of fine tuning to finally get rid of most of the bucking on my car with that same cam, pain in the ***..

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