Multiple Misfire P0300

[gearmesh, inc.]

Originally Posted by red99pony

wouldn't a compression leak down test show a broken valve spring?

Unfortunately, putting air in a cylinder with a leakdown tester just blows the valves shut and keeps them shut, despite low tension from a broken valve spring. Multiple coil valvesprings can even be harder to detect a broken coil by sight, especially if one of the inner springs is broke.

I have seen where a vacuum gauge can be used to diagnose a broken valvespring. However, at 5k+ rpm, any abnormal pulse reflected back into the intake may be too short of a duration for a mechanical gauge to react.

There are piezo transducers that are available that you can hook to a lab scope that can show a quick pressure abnormality at high speeds. Unfortunately, they are about $400 and up for a good one. Here's a link to one: http://www.aeswave.com/products/Prod...343&ci=84&sa=Y