Timing Mark Not Steady...

[TurboBlue]

Well yesterday i was testing out my knock sensor by watching the timing mark and hitting the block with a hammer. Found out th eknock sensor is indeed bad. But the weird part was, that even afterwards, while looking at the timing mark again, the mark never stayed right at 5 BTDC, it kind of swayed back and forth a few degrees in either direction. Anyone know whats causing this?

 

[Mike1992]

Mine does the same, I think its causing my shuddering every once in a while also HELP!

 

[steve]

Unless you have the check timing connector grounded the ECU is going to adjust the advance as it juggles the various parameters to keep you engine running.

Also keep in mind that the knock circuit is smart enough to to only pay attention to the sounds of knock when ignition knock is likely to happen. The ECU has crank angle information and knows than no ignition knock is going to happen when a a piston is halfway to BDC. So pounding on the block with a hammer isn't a really good test unless you get luck and hit at just the right time and make the right noise.

Steve