bucking
bucking Just got my car back from the shop,did a cam install and now my car bucks on low rpm's,1000-1600 rpms pretty badly.
comp cams
238/242 112.lsa
605/.610
Is bucking tuning related or the size of the cam? this is exactley what the tuner wrote
"With any cam you cannot go below 2000-2200 rpms. Thats the joy of a six speed just downshift.
comp cams
238/242 112.lsa
605/.610
Is bucking tuning related or the size of the cam? this is exactley what the tuner wrote
"With any cam you cannot go below 2000-2200 rpms. Thats the joy of a six speed just downshift.
How is your AFR at those RPM? If you are experiencing bucking while lightly on the throttle, I would guess it is running lean.
If it is not running lean, or the bucking occurs when you are not using any throttle and goes away when you apply a small amount, try increasing the throttle cracker airflow for the ranges you are experiencing bucking.
If it is not running lean, or the bucking occurs when you are not using any throttle and goes away when you apply a small amount, try increasing the throttle cracker airflow for the ranges you are experiencing bucking.
Backwards on this last part... if the bucking happening transitioning to no-throttle, your airflow is too high, either through the cracker or incorrect idle airflow values.
The car bucks off throttle,coming down in the revs and a little while driving, but not much at all. i have to tap the gas or let the clutch in to not hop..the lower it goes the worse the bucking.
just want the car to drive like it used too and not die and buck all over the place. im contemplating just putting my old stock cam back in or taking it to another shop, this has really fucked up my day(s)
Last edited by ls1n00b; Jan 18, 2008 at 06:36 PM.
238/242 112.lsa
That tight LSA and generous amount of overlap will take a lot of work to get smooth and still idle well with a 6-speed. Your tuner will have to spend a while with it, and may need to keep it more than a day to have good startups as well.
The trouble here, is that the amount of base airflow needed to get a solid idle, and the amount that cause the bucking sit on a fine line... too little and the bucking is gone, but it doesn't idle well; too much and it idles well but it bucks. This is even AFTER your cruise timing has been greatly reduced. If I were tuning the car, I would schedule plenty of extra time to get the driveability right. It really will take a lot of work, and there may be a bit down by 1000-nearly 1200 RPMs that just can't be gotten rid of with a 6-speed and still have it idling. If it is bucking past 1400-1500 or so there is definitely work to do. It would all be gone or unnoticeable with a stalled auto. He could have eliminated most of it when he was working on it, and it may have been great that day, but need some touching up again a few later.
Rather than have it retuned somewhere else, maybe try to get your tuner to spend a little more time with it.
That tight LSA and generous amount of overlap will take a lot of work to get smooth and still idle well with a 6-speed. Your tuner will have to spend a while with it, and may need to keep it more than a day to have good startups as well.
The trouble here, is that the amount of base airflow needed to get a solid idle, and the amount that cause the bucking sit on a fine line... too little and the bucking is gone, but it doesn't idle well; too much and it idles well but it bucks. This is even AFTER your cruise timing has been greatly reduced. If I were tuning the car, I would schedule plenty of extra time to get the driveability right. It really will take a lot of work, and there may be a bit down by 1000-nearly 1200 RPMs that just can't be gotten rid of with a 6-speed and still have it idling. If it is bucking past 1400-1500 or so there is definitely work to do. It would all be gone or unnoticeable with a stalled auto. He could have eliminated most of it when he was working on it, and it may have been great that day, but need some touching up again a few later.
Rather than have it retuned somewhere else, maybe try to get your tuner to spend a little more time with it.
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Ill be in houston Texas training another shop on the first of feb. and if you are in that area, you can come over and ill tune it all for free. It will idle at 600 rpms if you want and idle smooth.
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Mine (G5x3, slightly smaller duration cam than the OP) would buck at low RPM, low cruising speed with no throttle input. If I transitioned from no throttle input to a slight amount of throttle (<5%) the bucking went away, and was also alleviated by some added airflow for the offending RPM.
I never had any bucking transitioning to no throttle, nor with steady throttle input.
Would there be three separate scenarios and causes for bucking (lean at steady throttle, high airflow transitioning to no throttle, and low airflow for steady no throttle)?
Not trying to stir anything up, I am still learning.
Mine (G5x3, slightly smaller duration cam than the OP) would buck at low RPM, low cruising speed with no throttle input. If I transitioned from no throttle input to a slight amount of throttle (<5%) the bucking went away, and was also alleviated by some added airflow for the offending RPM.
I never had any bucking transitioning to no throttle, nor with steady throttle input.
Would there be three separate scenarios and causes for bucking (lean at steady throttle, high airflow transitioning to no throttle, and low airflow for steady no throttle)?
Mine (G5x3, slightly smaller duration cam than the OP) would buck at low RPM, low cruising speed with no throttle input. If I transitioned from no throttle input to a slight amount of throttle (<5%) the bucking went away, and was also alleviated by some added airflow for the offending RPM.
I never had any bucking transitioning to no throttle, nor with steady throttle input.
Would there be three separate scenarios and causes for bucking (lean at steady throttle, high airflow transitioning to no throttle, and low airflow for steady no throttle)?
I'm not gonna disagree, if adding air works for you, it works, but in my mind it would be like adding fuel to a car that swings up and down in OL.
