I have a 99 Flex-fuel Ranger which I've had the spark knock issues with I beleive I've cured for the most part by cleaning the mass air sensor and replacing the coil pack. I have a loud chatter most prominent when the engine is braking itself like when you top a hill and let off the accelerator and the engine is coasting or if you back off the gas just a hair you hear it the most.It would neither spark knock or chatter when cold, only after warming up.You can hear it during acceleration but is alot more evident when backing out of it.Could it be valves? Or heavy carbon build up? I,ve done a seafoam carbon clean a couple of times. Anyone came across this issue? Thanks.

 

Hellow! I'm new to this forum, but I'll try to help you! Have you pulled codes? It probably may help to understand what is going on. The first hypotesa - ignition timing, but to ajust it you need a scanner... Sometimes, but rarelly these symptoms may appeare caused but incorrect position of Crankshaft position sensor, spark plugs that dont fit this engine, bad fuel of low octane ratio.... I have '89 aero, but it is easy to ajust ignition timing becouse I have distributor, but I used to correct ignition timong of GM cars with TECH-2...

 

Welcome!

The rattling noise could be a loose exhaust heat shield. They have a tendency of coming loose and can sometime sound sorta like engine spark knock.

 

It is Difficult to answer your quation, becouse I can not hear noise, but exhaust shied noise and spark nock are different. Crankshaft bearing nock is different too. But if you are not sure I recomend you to use medical stetoscope to find noise location. I used this method too.