5.7L hemi #6 Cylinder misfire

Here is the deal with the new hemis and why they misfire...

The spark plug positions on each cylinder are very sensitive to fouling. When I tuned the 6.1 MP crate I put into a '59 Coronet, it fouled the first set of plugs after five minutes, due to a slightly rich condition showing on the AEM. They do not like anything, but perfect, iridium plugs.

A lot of the 5.7s have a serious valvetrain issue. Chrysler shows an update on new valve springs, due to people constantly breaking them from excessive heat.

There is a tag on these vehicles that recommends mid grade or better fuel. You can run regular, but when you do, you stress the cylinder head and its components.

The ECU can take timing out of the new hemis, but it cannot lower static compression below what they are, which I believe is somewhere in the 9.5:1 range or better.

So, even if the ECU picks up a KR signal from detonation and backs off all of the timing, it is still going to throw tons of exhaust gas temp through the roof, under load, on regular fuel.

The best thing you can do to a new hemi is run at least mid-grade and if you live in the hills or tow, run premium when you need it, as well as a synthetic or synthetic blend oil, to help drop engine and exhaust gas temps.

My friend's Durango just broke a valve spring. He took it to his friend, who is a fleet mechanic for the Arvada Police that has already replaced the springs in six of their fleet trucks and discovered this issue.

Be sure that its not just a lifter. You may have a crushed, collapsed, weak or broken valve spring.

If I ever own a 5.7 or 6.1, the first thing I am doing is replacing all of the valve springs.

Hope this helps.