To 7M, 1JZ/2JZ n/a owners. 4-6cyls problem

[George]

Ok so here's once more my 1jz-ge vvti.
Problem: poor driveability, bad mileage in city conditions. It isn't really that bad I can't drive at all, after all my car does 1/4 mile in the same 15.5sec like a jzx90 Cresta goes, which is 200kg less in weight but has no vvti and only 4-speed a/t.

Back to the problem, diagnosed reach mixture (Long Fuel Trim is -20% when idling in P, -15% in D, goes rapidly to +5% when further loading the engine)

Among other things, thought it may be bad combustion in some cylinders which would lead to oxygen sensor seeing some fresh fuel. Or excessive amount of crank gas. Testing for these two things resulted in following


Test 1. Removed crank ventilation
LFT -15% (P), -11% (D)
-the problem is there, but not very significant

Test 2. Disconnected injectors 1 by 1. Initial LFT -15.6% (P)
1 +10.1
2 +6.21
3 +6.99
4 -1.5%
5 -1.6%
6 -0.82%

Looks like cylinders 4-6 are stuffed up somehow. Maybe carbon deposits because of crank ventilation (that's fed exactly to 4-6 cylinders). Or plug wires (1-3 cyls are connected directly to the coil packs; I assume the packs themselves are ok because of rather adequate figures for 1-3 cyls)
Is there anyone that dealt with something like the above?
[edit] in particular, are there common reasons for cyls 4,5,6 to be different from 1,2,3 - carbon, valve clearance etc etc?

[George]

p/s My best guess is the following scenario: too much oil in crankcase ventilation (that Test1 clearly shown)led to coking cyls. 4-6 (which consume most of crank ventilation gas in idle/low load modes) => loss of compression. Unfortunately I can't check it right now being ill sitting at home.

I'll ask my question more clearly - if anyone ever rebuilt n/a 7M / 1JZ, was there any significant difference in 1-3 and 4-6 cylinders? With difference I mean carbon buildup and loss of compression.

Turbo rebuild experience is a bit different cause crank ventilation is arranged in another fashion in GTE's.

[George]

solved, it's oil rings
would decoke then decide what to do
if decoking helps would change stem seals and use the engine as is