Dane500

So lately I have noticed the 550 is knocking/pinging like it has crappy fuel in it. I cannot feel any reduction in power or response. This only happens (as I can hear) at 25-35 mph under light load....like slowly rolling into throttle. I can only hear it when my windows are rolled down. I keep over a half tank of premium in the car at all times. I use 1 gas station. I'm going to try a couple of things here first. New gas station, then a direct fuel injection additive just to rule out fuel. If it's not that....I would possibly suspect a failing delivery pump (I would think power would be affected and a CEL), or the timing chain is getting worn to the edge of spec ( I would also think power and CEL). I usually drive this car 50/50 sport/economy. Does it in both settings.

Any thoughts?

Cheers!

Dane500

Side note....have searched the forums and read on similar topic, but no real explanation or solution. My pump has 93. I am aware the vehicle will retard timing when the knock sensors pick up detonation. I think it only does that when the load is over 30% relative to speed. In my experience timing retard under any load can be felt.

S. Madman

You are going to have, to monitor you sensors in real time with a scanner. Also check you exhaust for leaks and loose heat shields. I would have someone else rev the car slowly thru the RPM range, while you look around for resonance.

S-Prihadi

If your regular workshop has in cylinder pressure transducer and 4 channel Pico Scope, maybe it can shed some light to how is the actual firing waveform on any suspect cylinder/s they may find,
which caused the knock. An experienced person/tech can tell A LOT from cylinder pressure waveform.

Dane500

I'll keep that in mind thank you. As of right now, different station with 93 and a long drive and it's gone away. Methinks in these trying times maybe all three pumps have regular. Who knows. I wouldn't normally make a big deal out of this but these are turbocharged....knocking is a bad thing.

S. Madman

If you still have some old fuel on it, get some octane booster.

Dane500

Just found out the gas station I WAS using has been nailed 3 times in as many years for fuel grade. Makes me think the coffee I get from there is somehow always decaf.