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Q: car jerks/gas pedal

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I have a 2004 Altima 2.5S (Automatic). The car slightly jerks when shifting gears (much more noticeable in downhills) and that's frustrating in traffic because the car wants to change gear from 1 to 2 but I press the brake and that's a bad jerk. I have taken the car to 3 transmission shops and they all did a road test and said there's nothing wrong with the transmission. Also No fault code exists. At idle (P) when I give some gas to 3000 rpm, the rpm needle sticks at around 1500 on return for 1-2 second, then comes back down to 900. Looks like the gas stuck somewhere in engine. I had already cleaned the throttle body but no relief! Have this issue for 8-9 mounts and that's not getting worse nor getting better. Only one or 2 times when I turned the A/C on, the problem went away and the gas pedal became enough stiff and satisfactory. I think this problem appeared after I changed my dead alternator myself.

My car has 138 miles.
My car has an automatic transmission.

A: Hi, thanks for writing in. This is more tha...

Hi, thanks for writing in. This is more than likely a fuel delivery issue, given the symptoms you describe. The idle air control valve is a unit that regulates the air flow into the engine as it is mixed with fuel prior to being injected into the motor. When this is not working properly, this will cause an imbalanced load of air and fuel to be supplied to the motor resulting in a loss of power or stall as you have experienced. This may also cause the car to have an irregular idle as you have described. I would recommend having an expert from YourMechanic come to your home or office to confirm a diagnosis on the issue and make or suggest the necessary repairs or replacements.

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