I had to replace the heads on my engine in April every since that time my car knocks within the 1st 20mins of starting the car up, the knocking seems to be coming from under the car. When it is warm out side it doesn't knock. lately it has been knocking everyday since it is colder out side.
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Re: Car is knocking
Sounds like a bad connecting rod bearing or a carbon knock, de-carbon the engine and retest for noise, if it is still there the engine will need to be torn down the crank refinished and new bearings installed.
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Check engine light on ? What code ? There are many different (DTC'S) - diagnostic trouble codes that can set for knock sensors ! There all don't mean that you replace the sensor .
DTC P0324: Knock Sensor (KS) Module Performance
DTC P0325: Knock Sensor (KS) Circuit Bank 1
DTC P0326: Knock Sensor (KS) Performance
DTC P0327: Knock Sensor (KS) Circuit Low Bank 1
DTC P0328: Knock Sensor (KS) Circuit High Bank 1
DTC P0330: Knock Sensor (KS) Circuit Bank 2
DTC P0332: Knock Sensor (KS) Circuit Low Bank 2
DTC P0333: Knock Sensor (KS) Circuit High Bank 2
The knock sensor (KS) system enables the control module to control the ignition timing for the best possible performance while protecting the engine from potentially damaging levels of detonation. The sensors are located below each cylinder head on the engine block. The KS produces an AC voltage signal that varies depending on the vibration level during engine operation. The control module adjusts the spark timing based on the amplitude and the frequency of the KS signal. The control module receives the KS signal through 2 isolated signal circuits. The control module learns a minimum KS noise level at idle and uses calibrated values for the rest of the RPM range. The control module should monitor a normal KS signal within the noise channel.
Knock Sensor Replacement - Bank 1
Remove the exhaust manifold lower heat shield. Refer to Exhaust Manifold Lower Heat Shield Replacement.
Disconnect the engine wiring harness electrical connector (1) from the bank 1 knock sensor (2).
Loosen the knock sensor bolt and remove the knock sensor.
Knock Sensor Replacement - Bank 2
Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection .
Remove the engine oil filter. Refer to Engine Oil and Oil Filter Replacement .
Lower the vehicle.
Disconnect the engine wiring harness electrical connector (2) from the bank 2 knock sensor (3).
Loosen the knock sensor bolt and remove the knock sensor.
you fail to menyion what kind of car and which engine. I can only guess that this is what is known as spark knock which can be caused by several things, most common would be low octane fuel. another more critical cause could be improper timing.
The knock sensors (one for each cylinder head on the V6) are located on the inside of the cylinder heads, in order to replace them the upper intake manifold must be removed. It is always recommended on this engine family that not only replace the 2 knock sensors but that you also replace the short sub wiring harness to the knock sensors from the main engine harness as it is many times the a common cause of the knock sensor code(s) in the 1st place.
Often a single issue can trigger multiple diagnostics codes, especially if the circuits are closely related.
Code P0100 = Mass Air Flow (MAF) Circuit malfunction
The computer has detected an issue with the MAF sensor.
- Verify the MAF sensor wiring is connected and wiring is in good condition
- Unplug and reconnect the MAF harness
- Check that voltage to the MAF sensor is within factory spec
Code P0325 = Knock Sensor # 1 Circuit malfunction
A knock sensor tells the engine computer when one or more of your engine's cylinders are "knocking", that is, exploding the air/fuel mixture in a way that delivers less power and can be damaging to the engine if prolonged. The computer uses this information to tune the engine so that it doesn't knock. If your knock sensor wasn't operating properly, so that it was always indicating a knock, the engine computer's response may have been to change the ignition timing on your engine. Knock sensors generally bolt into or thread into the engine block.
- Check condition of the knock sensor wiring.
- Test the 'Ohms' reading of your Knock Sensor (undo the connector and measure the pins) to ensure it is within spec (ask Nissan for this measurement). If out of spec, replace the knock sensor.
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Need more info, what kind of noise. How many miles are on your car.What engine is in your car. If the noise sounds like an engine knock, have someone take the tension off of the belt while you check to see if Harmonic balancer moves back and forth. If it does it needs to be replaced. It will sound like an engine knock when bad. When this 1st starts to go bad it is only there part of the time. If it is this, it will eventually be there all the time and get much worse.
Check the engine for compression. Your head gasket may be shot. I have a 97 that had a similar problem, and we did the head gasket, car runs fine now. Prior to doing the gasket mine wouldn't start at all.
if you think the head gasket is blown,and now you have a knocking in the engine,replace engine, bearings are probably bad due to water in the oil.you will need special tools to even do the head gasket and timing belt. sorrry no good news
A knock sensor is simply a microphone that is screwed into the engine block. It is there to listen for pinging or engine "knock" that is caused by poor fuel or extreme load. When the computer hears the knock, it retards timing, which in turn reduces the tendency for knocking, however, it will reduce power to a certain extent as well. It is possible that a faulty knock sensor can be telling the computer to ****** ignition timing too much, it is also possible that there is a mechanical problem within the engine that is mimicking the sound of knocking and retarding timing as well.