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Bank 1
see if it really is that rich.
16% rich is like 12.3 Afr on a wide band. If so,
why is it so rich on a stock tune?
when it goes into PE it's rich.
That's what rich looks like with that program
I know nothing about computer tuning.
HOWEVER
I see folks saying that the engine is "rich" based on the fuel trim numbers shown in the graph. This is NOT correct.
Fuel trim numbers do not show rich/lean air/fuel ratios.
The O2 sensor can show rich/lean, but only if there's no misfire. If there's misfire, the signal is corrupted by the presence of the oxygen that did not combine with the hydro-carbon fuel to produce water vapor (H2
O) and carbon dioxide (C
O2). Misfire produces a false-lean indication.
Fuel trim numbers less than 128 (the way I'm used to seeing it presented by the scan tool) or showing a percentage reduction does not indicate "rich", it indicates "
Lean Command". The computer is compensating the fuel delivery based on the O2 sensor signal, reducing the amount of fuel that would otherwise be required by the base programming (tuning.)
The fuel mixture delivered to the cylinder is still correct, the mixture is not actually "rich".
"Running rich" and "Lean Command" are not the same thing.
If this engine is misfiring at idle, the upstream O2 sensor(s) should be showing a false-lean condition, leading to Rich Command. If it's not, things are double-weird. What are the misfire counts per cylinder? Are the misfires genuinely "random" or are they confined to certain cylinders? What are the O2 sensor voltages, and cross-counts if that info is available?
To my thinking, fix the misfires first, reconsider the computer tuning second. The computer tuning is not so far off that it's actually causing a rich air/fuel ratio. The computer is still within the range of compensation for the tuning.
You've replaced a heap of parts, but I don't see that you've tested most of them first--or afterward. I'd be looking for a spark-tester calibrated for HEI, and see if the coil can jump the gap reliably when the tester is connected to the spark-plug end of the plug wire leading to every cylinder that shows misfire. This tests the coil, coil wire, distributor cap, rotor, and the plug wires themselves. It does not test for spark plug problems--cracked porcelain, fouling, etc.
Installing a timing set "dot-to-dot" can be done by GM using their "validated" parts, especially since 90% plus of their customers wouldn't know the difference if the cam timing were five degrees off. Using less-reliable aftermarket parts and installing "dot-to-dot" is a total crapshoot. I at least check the "degree" of every cam I install, because if there's a problem later, I don't have to worry about cam timing being a contributor.
You
MIGHT be able to confirm camshaft position by putting #1 (or #6) on TDC EXHAUST (NOT TDC-Compression!!!) and looking at the valves. Both valves should be very slightly open on overlap. I'd expect the intake to be open a hint more than the exhaust. If the exhaust is open more than the intake, the cam is retarded. If the intake is open a bunch more than the exhaust, the cam is advanced. Problem is, with hydraulic lifters, they may bleed-down so fast that cam-lobe position is lost to the plunger collapse.
Another method that might work--kinda--is to look at the distributor housing position, with the cam and crank synchronization adjusted as close to "perfect" as possible. If the distributor is rotated more than a couple degrees from it's usual position, the cam timing is suspect. The problem with this method is that you'd have to have a really-strong sense of the "correct" distributor position, and we've seen problems with aftermarket distributors not having proper alignment to begin with. Distributor gear wear, and wear on the gear on the back of the cam could also affect distributor position.
