well it can be a numerous amounts of things mine was knockin cause i had a few bent teeth inside the harmonic balencer changed it.....and no knocking.....! 100 dollar part. if you dont get it fixed when you got the cash it will lock up and throw your belt causing nothing to work... the car will overheat fast and your Power Steering will go out and im not for sure but it threw my water pump pully out of line.......or it could be no oil or a rod knocking..........Its alot better to get it fix right away....!
The knock sensor is a passive device that has no effect on engine idle.
There are a number of reasons why an engine would knock when you idle the vehicle. It could be your motor mounts. You may also need oil.
Added info to question: Vacuum also coincidently went from steady 20psi to 15psi/knock - small backfire/miss on acceleration from idle. Knock is steady at idle.
The knock sensor has no effect on idle. It has no effect at all unless it is triggered by detonation. It is a passive device.
Could be the idling sensor or the EGR Valve
Perhaps the throttle plate is stuck - try to free with a screwdriver
vaccum leak
There are a number of reasons why a 1991 Toyota Corolla engine would stop running after startup. It could the idle control, an EGR leak, or low fuel pressure.Ê
The Throttle body is where all the sensors are for this car. If your having an Idle problem though, It is rarely that.
Check Related Link below. It shows you a picture too.
A faulty camshaft can cause your 1991 Nissan Maxima to idle erratically. A diagnostic test could verify the cause of the improper idling speed.
The idle is preset and controlled by the Idle Air Control Motor. You may have a dirty throttle plate that could cause a problem.