Quote:
Originally Posted by Scharbag
Just ran a can of sea foam through the intake. Pita to hold the car at 1800rpm without help. Thankfully I have some construction clamps that worked!!
I will re-flash to 91 octane stage 1 soon. Going to run a full tank of 94 with sea foam to give it a good chance to clean the tops of the chambers. Here is hoping.
Cheers,
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I can relate to this, as ever since this started showing on my S65 50k-ish miles ago I have been trouble shooting on and off to no real success. new spark plugs, new coils (individual cylinder and all 8), low fuel pressure sensor, upgraded OE software, aftermarket software, injector/fuel system cleaner, thought I tried them all. What I felt is these things provide temporary "relief" to the issue, but never fully "solve" the problem at root. The car would run smoother with each of these parts change/software flash, but eventually the knocking or low rpm pre-det returns. I actually get the knocking at high rpm as well sometimes, during certain throttle angles
I will say tho, putting in brand new coil packs all around and running Chevron Techron Concentrate Plus (in separate instances, not done at the same time) made the most dramatic improvement, especially the former as it instantly restored the urge/eagerness to rev on my aging S65, it was to the point where I could dial back my throttle input a little to achieve the same, or if not stronger, pace of acceleration as before. And the latter allowed the engine to run notably smoother and quieted down the (old) injectors. But nothing lasted, the det always slowly creeps back.
Like some of the guys here have mentioned, my main tech firmly believes it's octane induced given the lowly 91 premium fuel we get in CA. The one thing I never did remember to try was to run octane booster or mix in some race fuel to bring up the octane and run that for an extended period of time.
My latest attempt to address this seemed to have worked well so far - I replaced all of the injectors. And the past couple months have truly been knock free, especially in low rpm instances where sometimes I was caught being in one gear higher than where I needed to be in. Was supposed to send my old injectors out to get flow tested, just to see what kind of shape they were in, but i think the shop lost them...
Maybe with the crappy 91 gas being the only option available my injectors will eventually wear and develop the pre-det again, but just wanted to share my experience as the car has been a blast to drive the last 3 months without me ever thinking/worrying about triggering this noise