Chasing knock. I cannot eliminate it, nor can expert tuning.
knock CEL generally occurs around 3000 RPM on up, and has a somewhat intermittent nature. Knock will occur even with light throttle, and sometimes NO BOOST.
It does seem to have gotten worse with the higher ambient temps lately; it used to be just a nuisance that I could manage to a degree with careful/selective driving, now it's a fact of life.
- 2.3 motor w/stock compression ('96 HPT motor, all original)
- 19t 7cm AF w/ obx DP and high flow cat w/3" back to stock rear and R manifold
- recently installed brand new late style knock sensors w/integral harness
- do88 intercooler and rip kit
- genuine bosch greens from a 120k mile s60r, thoroughly cleaned and rebuilt.
- replaced exposed cone filter with stock airbox and cold air ducting
- NGK BKR9e-ix plugs (I've played with 3 heat ranges, ran stock, etc with no real change)
- motor torn down, freshend up, and all carbon deposits/etc cleaned up from pistons, chambers, valves.
- coil assembly swapped with another (no change)
- Cam timing established by setting engine up with the special tools, and adjusted accordingly for 3.5 degrees advance exhaust, 3 degrees retard inlet
- fuel filter, etc. All the usual stuff.
coolant temps APPEAR good, AFRs (wideband) are good, boost control is good, etc.
ignition timing has been reduced, reduced, and reduced again in the problem spots. That's actually an understatement.
Fueling also messed with over and over again in the problem spots.
Running 93 (r+m)/2 10% ethanol blend; I've tried multiple local fuel offerings on nearly empty tanks.
I'm starting to go mad. I can daily drive it just fine; but I can't really have any fun with it.
I was pretty anal with sorting everything out properly and "by the book" to get a fun and reliable daily driver... it's anything but.
Before bending a rod back in February, knock didn't seem as prevalent. Ever since getting the car back together it's been more of a problem. This could be due to higher ambient temps. Snow was on the ground back when things suddenly went wrong and the rod bent, but for the most part knock wasn't such a big deal... I had some awfully cold days after getting it back together and general success (compared to now) with doing runs, but since then it seems that knock has been an uphill battle.
I'm inclined to replace the thermostat and temp sensor just to eliminate them as potential culprits. I have a suspicion that I have a flaky/sluggish thermostat that is allowing enough coolant bleed to keep the localized sensor temps "normal" but the areas around the combustion chambers could be overheating.
I recently observed a correlation between needle position well after "warmed up" --- needle was reading below the normal range, it was a relatively hot day, and I got some good runs in with minimal knock.
I have not seen this behavior since, and I have not had any good runs since.
Any bright ideas here?