1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

car lurches when i let off the gas

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Old Oct 28, 2010 | 07:56 PM
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car lurches when i let off the gas

if i use the gears to slow down, it's steady for a moment, then it lurches, like i keep tapping the gas. is this normal? I've never been in a car that does that so i have no idea what to even think about doing.
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Old Oct 28, 2010 | 08:01 PM
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clutch? mine does that when i play with the clutch
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Old Oct 28, 2010 | 08:15 PM
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no, it's constant, if my feet aren't on any pedals, it lurches pretty much constantly until i press the gas or the clutch in. this is before it gets to a low speed, this is de-accelerating speeds.
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Old Oct 28, 2010 | 08:23 PM
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might be your gas pump, not enough gas is getting to the motor when the pedal is not pushed in.
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Old Oct 28, 2010 | 09:16 PM
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I'll have to check that. these have electric fuel pumps located back by the tank, right?
should I expect a steady stream or a trickle?
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Old Oct 29, 2010 | 06:48 AM
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What rpm does this happen at?

Does this happen if your say in 4th gear on the highway and let off the gas
and coast or is it when you down shift to let the engine help brake the car?

Below a certain rpm rotaries tend to buck and it can get exaggerated if your foot
is on the gas when it happens.
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Old Oct 29, 2010 | 10:03 AM
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it will do it if i coast, or if i use the engine to slow down. it seems to do it between 1500 and 2000 rpm's only. and only if my foot is not on the gas. i can put it in whatever gear and keep it at any rpm and it wont do it. so it's just the nature of the beast, eh?
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Old Oct 29, 2010 | 10:11 AM
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So is it in gear at 1500 to 2000 rpm when it does this or out of gear?
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Old Oct 29, 2010 | 01:40 PM
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In gear. I would not think the car could lurch out of gear
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Old Oct 29, 2010 | 01:59 PM
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It's not uncommon for rotaries, especially ported ones. What you're experiencing is dilution of the intake charge with exhaust gases causing misfires. It's the same effect that causes the distinctive "brap brap brap" idle of bridgeported and peripheral ported engines, just not as extreme.
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Old Oct 29, 2010 | 02:23 PM
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Oh, okay. Thank you. glad to know it's not something i got to fix.
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Old Oct 29, 2010 | 03:03 PM
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It is pretty common for decel when in too high a gear, especially in the 1500 rpm range. Also common for newbees to driving a round motor. It is telling you to use the brakes instead of the driveline to slow it down. Using the trans to slow a vehicle down (any vehicle) does more damage to the clutch, trans, rear engine bearing, driveshaft and rear which generally cost a lot more to repair than replacing brakes.
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