Bucking in 2nd Gear
Thread Starter
Pro
Joined: Oct 2016
Posts: 523
Likes: 90
From: Los Angeles, CA
Bucking and surging after cam install
Car is a 2004 C5 Z06. Major engine mods include:
LG Super Pro 1 3/4" Long tubes with catted x-pipe
LG G5XE Cam/Comp 921 Valvesprings
Ported 243 heads
Vararam Intake
Dyno Tune
Soon as I get below 1000-1100 rpm, the car starts jerking and bucking, the lower in the rpm range I get, the worse the bucking gets. Also, when the engine is hot/outside temps are over 85 degrees, engine doesn't want to turn over. What could be causing these issues? I know it's a tuning issue but it seems the tuner that did the original tune after the cam install is having issues fixing these issues.
Would having the stock fuel injectors be causing these issues? Or maybe the vararam? Anything else that could be causing the hot start issue and low rpm bucking and surging?
Car put down 450rwhp/430rwtq and runs strong but I also feel that it may not be running as strong as it could.
LG Super Pro 1 3/4" Long tubes with catted x-pipe
LG G5XE Cam/Comp 921 Valvesprings
Ported 243 heads
Vararam Intake
Dyno Tune
Soon as I get below 1000-1100 rpm, the car starts jerking and bucking, the lower in the rpm range I get, the worse the bucking gets. Also, when the engine is hot/outside temps are over 85 degrees, engine doesn't want to turn over. What could be causing these issues? I know it's a tuning issue but it seems the tuner that did the original tune after the cam install is having issues fixing these issues.
Would having the stock fuel injectors be causing these issues? Or maybe the vararam? Anything else that could be causing the hot start issue and low rpm bucking and surging?
Car put down 450rwhp/430rwtq and runs strong but I also feel that it may not be running as strong as it could.
Last edited by harryk387; Jun 25, 2017 at 11:25 PM.
Drifting
Joined: Jun 2013
Posts: 1,290
Likes: 360
From: Iowa
I'm interested as well. Occasionally, I'll get bucking when off the throttle, in gear, with low RPMs, while decelerating. Giving a little gas corrects the problem. My car is stock except for a vararaam, x-pipe, and exhaust.
Last edited by Macleod52; Apr 25, 2017 at 04:01 PM.
Thread Starter
Pro
Joined: Oct 2016
Posts: 523
Likes: 90
From: Los Angeles, CA
Drifting
Joined: Jun 2013
Posts: 1,290
Likes: 360
From: Iowa
Racer
Joined: Feb 2015
Posts: 299
Likes: 33
From: Chambersburg PA
I would expect that at 1000-1100 rpm in second gear slowing to stop, it's speed, rpm, gear ratio and load. I would expect bucking worse in 3rd gear in that situation. Heck all manual trans cars will do that if speed is to slow for gear selected. It's not an auto so won't act like one. Heck it will even do that in first if wheel speed slow enough.
And yes depended on the cam this will be exaggerated, all is normal just drive it like a manual and not an auto.
And yes depended on the cam this will be exaggerated, all is normal just drive it like a manual and not an auto.
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2020 Corvette of the Year Finalist (performance mods)
C5 of Year Winner (performance mods) 2019
why are you lugging the engine at such low rpms?... any car will buck if you let the rpms drop low enough and your car has a decent sized cam and making good power so that may be all it is... quit driving it like a baby
... if you have stock injectors you should look into replacing those, your tuner should be able to tell you the duty cycle but my stockers were damn near maxed around 420rwhp... as far as the hot start issue maybe have the battery checked, heat will finish them off when they are weak and on their way out
... if you have stock injectors you should look into replacing those, your tuner should be able to tell you the duty cycle but my stockers were damn near maxed around 420rwhp... as far as the hot start issue maybe have the battery checked, heat will finish them off when they are weak and on their way out
Last edited by StingrayRebel; Jun 26, 2017 at 12:08 AM.
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From: Kelowna BC
why are you lugging the engine at such low rpms?... any car will buck if you let the rpms drop low enough and your car has a decent sized cam and making good power so that may be all it is... quit driving it like a baby... if you have stock injectors you should look into replacing those, your tuner should be able to tell you the duty cycle but my stockers were damn near maxed around 420rwhp... as far as the hot start issue maybe have the battery checked, heat will finish them off when they are weak and on their way out
... if you have stock injectors you should look into replacing those, your tuner should be able to tell you the duty cycle but my stockers were damn near maxed around 420rwhp... as far as the hot start issue maybe have the battery checked, heat will finish them off when they are weak and on their way out
Thread Starter
Pro
Joined: Oct 2016
Posts: 523
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From: Los Angeles, CA
I don't think having it buck violently around 1000 rpm is normal with this cam considering it's supposed to be a street able daily drivable cam. Also, I don't know about you guys but when I'm driving around a parking lot looking for a spot I'm not flooring the gas pedal, I'm usually in first gear with my foot off the gas coasting at idle. Don't consider that necessarily babying it. Same with bumper to bumper traffic. I've had other manual transmission v8 cars and have never had this issue with those cars.
For the hot start issue, have this issue even after new battery installed.
For the hot start issue, have this issue even after new battery installed.
Intermediate
Joined: Jun 2015
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https://youtu.be/f9JZoNWhzrs
Here's a link to a video of my hot start issue. Will try to get a video of the bucking as well. It feels more like a tuning issue to be honest.
Here's a link to a video of my hot start issue. Will try to get a video of the bucking as well. It feels more like a tuning issue to be honest.
Team Owner
Joined: Mar 1999
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From: At the beach in little Rhody
It's most likely the overlap in the cam. My cam is slightly smaller and does the same thing. Just one of the things you have to work around with a cam sometimes. I just drop another gear to get the RPM out of the range.
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looking at your video I think the tune needs to be cleaned up, it might have too much fuel or not enough at startup but it definitely shouldn't do that
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From: Granby, MA
Cruise-In 1, 3, 9. 10 & 11 Veteran
Definitely Absolutely tuning issues! That fact that your gut is telling you this should alone be enough. Lets review....
Car put down 450rwhp/430rwtq and runs strong but I also feel that it may not be running as strong as it could. For a Z06 cammed with ported 243 heads car, these numbers are almost dead on when just doing a simple google search to see what others were able to accomplish.
Would having the stock fuel injectors be causing these issues? Or maybe the vararam? Anything else that could be causing the hot start issue and low rpm bucking and surging? Being you are running the stock injectors, this would be a great question for a new tuner to investigate. Just common sense logic would point me to you having a fuel issue or a spark issue upon startup. (there can't really be anything else). Have the tuner look at the car when you are having the hard start issues...my guess it something is going to turn up in the tune.
This leads us to your statement, that to me...sums it all up!
I know it's a tuning issue but it seems the tuner that did the original tune after the cam install is having issues fixing these issues. Its clear you're not happy or confident in your tuner. Nothing can be worst then that. Not trusting someone fooling around with your car just plain sucks! Definitely seek out another tuner. Call around, put up a post asking for recommendations and someone that comes highly qualified in your area. Good Luck! You'll get it sorted out, you just need someone who knows their stuff to take a look at it! I could offer recommendations like anyone on here but quite honestly, you really need a qualified tuner to look at the car. Way too many variables just to just make a general consensus and might end up having you go down the wrong path.
Car put down 450rwhp/430rwtq and runs strong but I also feel that it may not be running as strong as it could. For a Z06 cammed with ported 243 heads car, these numbers are almost dead on when just doing a simple google search to see what others were able to accomplish.
Would having the stock fuel injectors be causing these issues? Or maybe the vararam? Anything else that could be causing the hot start issue and low rpm bucking and surging? Being you are running the stock injectors, this would be a great question for a new tuner to investigate. Just common sense logic would point me to you having a fuel issue or a spark issue upon startup. (there can't really be anything else). Have the tuner look at the car when you are having the hard start issues...my guess it something is going to turn up in the tune.
This leads us to your statement, that to me...sums it all up!
I know it's a tuning issue but it seems the tuner that did the original tune after the cam install is having issues fixing these issues. Its clear you're not happy or confident in your tuner. Nothing can be worst then that. Not trusting someone fooling around with your car just plain sucks! Definitely seek out another tuner. Call around, put up a post asking for recommendations and someone that comes highly qualified in your area. Good Luck! You'll get it sorted out, you just need someone who knows their stuff to take a look at it! I could offer recommendations like anyone on here but quite honestly, you really need a qualified tuner to look at the car. Way too many variables just to just make a general consensus and might end up having you go down the wrong path.
Last edited by XtremeVette; Jun 29, 2017 at 04:52 PM.