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Q: Engine problem - 2009 Toyota FJ Cruiser

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hi

i have 2009 toyota fj cruiser manual transmission

there is problem: 1- sometime i hear knock sound if drive car from 0 mph with 2nd gear

2- if i press brake pedal, rpm idle drop down to 400

3- sometime my engine shake quick just 1 second (look like you turn the key off and you turn on quick)

but this 3 problem not always happen only once a day

4- my car become very slow and no torque hard to reach 80 mph

but i do everything change (air filter, spark plugs, fuel filter) clean throttle body and clean fuel injection

but nothing change still same problem

thanks

My car has 120000 miles.
My car has a manual transmission.

A: Hello. A knocking sound when starting from ...

Hello. A knocking sound when starting from a stop in second gear is to be expected. This sound will come from either the motor or the transmission. I don’t recommend starting off in second gear. It isn’t good for your car. It can contribute to premature transmission and or clutch failure.

Admittedly, most cars can begin in second gear with only minor issues. Mainly it will wear your clutch out sooner than normal. The pressing the brake pedal that affects your idle is most likely a leaking check valve in the hose that goes to your power brake booster. This creates a vacuum leak when you depress the brake pedal. It is possible the check valve is causing these other problems under different conditions. You should be able to disconnect the vacuum hose to the brake booster without creating a vacuum leak. If a leak exists when you disconnect the vacuum line, replace the check valve.

A few things I would be doing aside from what I have already stated. I would inspect for vacuum leaks, connect a scanner and study the data and clean the IAC (idle air control) valve.

If you should need further assistance, I recommend having a certified pro, like one from YourMechanic, diagnose the misfiring symptoms and perform the appropriate repair.

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