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can someone tell me why when i put a new vaf sensor on my car which was the same as the old the engine pinked (preignition) jst once on startup, it has done it when i put a dsecond hand throttle body and vris valves on too, the parts are all the the same as the ones taken off. is this normal or is it a fault?

Not sure what you mean man, can you clairfy what you are saying? A better title may help to to get more views.

Your saying it pings once every time you change out a part and then stops immediately following? Are you disconnecting your battery each time you change out a part? If I am following you correctly.. this is probably because your initial timing is set too far advanced. The initial (or base) timing is used when you start your engine. After the engine is running.. the ECU gathers information from all the sensors on your engine and determines the best timing for the engine to operate the most efficiently. If the Knock sensor detects a ping.. it will send a signal to the ECU.. the ECU then retards the timing accordingly. Each time you disconnect the battery.. the ECU is losing its saved data regarding the timing the engine should be adjusted to. Just a couple of thoughts..

Tunes67

P.S. This is different from the B6 4cyl engines.

no i dont disconnect the battery just keep the ignition off. since yesterday the engine has pinged about four times all just on start up but never when moving. the car seems to act differently when it pings ie: smells of fuel from exhaust and seems slower then it will ping sometime later and the smell will go and the car will be normal its doing this all the time. mazda dealer dont know what it could be but they tried to plug in the diagnostic computer and the ecu wont communicate. does anybody know what other factors cause engine ping apart from running lean and timing which has been checked.

forgot to add when engine has pinged and its runnind slower the idle will drop for a second then come back to normal when coming to a stop and clutch depressed. but when engine is running fine the idles dont do that.

Since your in the UK.. you dont get CEL codes.. and I am not sure how to get the CEL Code equivalent for you.. but.. at a guess.. I'd bet your knock sensor is going bad. Find a way to check the ECU trouble codes.. I am sure the information is somewhere around this website.. it has to have been discussed before. Best of luck.

Tunes67

Tunes67 wrote:Since your in the UK.. you dont get CEL codes.. and I am not sure how to get the CEL Code equivalent for you.. but.. at a guess.. I'd bet your knock sensor is going bad. Find a way to check the ECU trouble codes.. I am sure the information is somewhere around this website.. it has to have been discussed before. Best of luck.

Tunes67

Search function...

I think if you jump FEN and GND with a test light it will mimic the CEL...

I would reset base timing and reset the ecu, after you pull codes of course.

I agree with the last two posts.
10 and GND with a test light to pull codes- the ECU and then check the timing, if off reset timing.

thanks for the replies. i had the ecu checked at my local mazda dealer and there was no codes stored. they think it could be timing belt tensioner moving making timing jump when first started and then causing ecu to compensate by retarding/advancing timing. is this possible? if it was would it not click every start up?

Yes its possible. If its not the Knock sensor going bad.. then the timing belt tensioner is the other item that could cause a similar symptom.

Tunes67

man are you sure your just not mistaking this sound for your lifters making clacking on start up..

its definately not the lifters. its just one click, i disconnected the knock sensor and the noise still happened.