engine strange bucking after 3000 rpm
10-21-07, 12:50 AM
#1
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engine strange bucking after 3000 rpm
whatsup
posting this question for a friend
his sc300 na-t bucks after 3,000 rpm
car has been fine in the past, there's more then enough fuel.
He has a small turbo with a walboro pump, 440's, v8 maf, and AFC2.
before 3,000 rpm the car is fine, even if getting on it hard at hitting 5lbs of boost.
BUT after the rpm needle crosses over 3k, it starts to buck randomly. The wideband so random lean a/f ratios
even if the afc is adjusted real rich, and the a/f show very rich it will still hit a lean spike. And this is regardless of throttle position, boost or vacum while cruising.
Anyone know if the engine switch something on or off at 3,000 rpm???
so far no check engine lights....
strange....
posting this question for a friend
his sc300 na-t bucks after 3,000 rpm
car has been fine in the past, there's more then enough fuel.
He has a small turbo with a walboro pump, 440's, v8 maf, and AFC2.
before 3,000 rpm the car is fine, even if getting on it hard at hitting 5lbs of boost.
BUT after the rpm needle crosses over 3k, it starts to buck randomly. The wideband so random lean a/f ratios
even if the afc is adjusted real rich, and the a/f show very rich it will still hit a lean spike. And this is regardless of throttle position, boost or vacum while cruising.
Anyone know if the engine switch something on or off at 3,000 rpm???
so far no check engine lights....
strange....
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10-22-07, 07:36 PM
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try some minor adjustment with the TPS - my V8 was doing something very similiar and was leaning out like crazy hence the bucking - mine was coming back down the rev range and came in about 2000rpm
Last edited by lxsv8; 10-22-07 at 07:44 PM.
10-23-07, 12:15 AM
#11
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i had the same problem also, and it turned out to be the plugs. I read on supra forums to re gap them to about .028 as i had them at .039. That seemed to fix the problem for me
10-23-07, 01:25 PM
#12
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hmmmm, wouldn't the fuel have ignited by the time it was in the exhaust manifold? Since there is where the O2 is, it should have registered rich? no? just wondering.....
He's gonna pull the plugs anyways to see what they look like, maybe that will give a clue as to what's going on inside the engine
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