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Comments
Let me put another theory out there. My first idea was mechanical fuel restriction which is simple and unlikely, and probably wrong.This theory is complicated and unlikely, but we can all agree we are looking for an unlikely cause.
Your firing order has changed from 1-8-4-3-6-5-7-2 to 1-3-5-7 and then 8-4-6-2.
This would explain:-
Odd colored plugs
Odd noise
Laboring engine
Reduced RPM
It would not, however explain your strange fuel rail pressure drop.
What I am saying is the engine is effectively going into guardian mode and not telling you. This would require at least two subtle faults. In guardian mode the ECU ( I think) inhibits injection on odd numbered cylinders for one cycle and then even numbered cylinders for another cycle.The reason I have asked you to use a "colortune" plug in previous posts is so that you could see the missed combustion. You would get - induction - compression - spark only - exhaust and then - induction - compression - power - exhaust.
Engines do not lie to you, scanning tools often do.
Does this make sense to anyone?
Am I talking through my hat?
Do you know if i need a 10,12 or 14mm? This color tune is pretty cool. Not sure it is going to help me but Im so exhausted on this I'm willing to try
Dream 'Inn III -- 2008 400 Express
14 mm, offer it up to a plug to be double sure.
PC BYC, Holland, MI
Both fuel sync and ignition timing is dependent on that mechanical alignment. One tooth advanced or retarded, or even a nylon liner thingy breaking free and causing slop could do it. That is one reason why I like gear driven timing or doubles, and always stay away from 'silent' chains with those stupid nylon/plastic liners between the links that cause slop as they wear... A combo of wear and indexed off one tooth could easily be your issue, again the computer compensating to a point but not beyond.
On most production interference engines there's only a few degrees near TDC where the piston will impact the valves, and the valves aren't opened within a few degrees of TDC becuase it would lose efficiency.
With the cam 90/180° out of sync I imagine the engine would run (although the firing order and ignition timing would be slightly off, so 1 is 6, etc.). On a V-8 I've run with the distributor 180° out - idled fine, but wouldn't rev past 65% throttle in neutral, and under load it was smooth but weak. I never thought that it was the distributor because the engine ran so smooth.
I think we're all looking forward to the diagnosis.
PC BYC, Holland, MI
as someone said "gauges lie, engines don't".
you gotta figure if fuel pressure isn't falling, injectors are actuating (properly), air isn't obstructed (also evidenced and related to fuel via valve events), cylinders aren't weak in compression (which could also be evidenced by bad valve timing/seats/weak springs/sticky lifter/miscalculated pushrod length, ect) and all of it is properly aligned (cam/crank relationship), and spark is being applied properly and in sync, it leaves only one and one only thing: demon possession.
i bet Al already deduced this, and why he didn't take it in for recovery...
the dang thing is possessed.
y'all don't think it got into @wildboating too, do you?
Number of comments 666.
@Wildboating come back!
have you made absolute certain your lifter rods are uniform length and same as port engine's? the cam's profile is one thing.... the rockers ratio is another... but the lifter rods play a vital role too- lift/duration is directly impacted by them- not lifting high enough or open too short a time- the flow of air and the injection is impacted not only by volume of flow but also the velocity of flow- and you realize you'll really know the difference up high in the curve... right where you're seeing it.
then there is the lifters themselves. which ones were used? softer springs or smaller passages also makes for variations in lift/duration. likewise, firmer springs with less cushion cause higher lift/duration- creating a more air than catalyst (fuel) issue, and burning lean... a touch lean, depending on the fuel used and it's additive pack (especially if MMT is in it for rand boost) will absolutely turn plugs orange near stoich ratio's... this could absolutely be your issue. you actually don't want stioch, not in a marine engine... you want to run a bit fat- 13.5:1 or so as opposed to 14.7:1 A/F.
then, valve lash- but i think we covered that before- messy job but easy.
now the plus won't lie. we established that. reading plugs is a lost art. orange means something, though. most often it means you've been running racing fuel that is considered racing fuel by virtue of rand (octane) rating alone- and achieved by treating lesser quality fuel with additives- additives containing MMT. it's notorious for it. you'll also get orange'ish plugs, though, when running lean.
you've been through your fuel systems and it seems okay, right? so.. you're getting fuel. if this holds true and your plugs aren't orange because of additives, that leaves lean. that means unmetered air if you know your fuel delivery system is g2g.... and we're back, now, to something happening high in the range that allows the engine to fall flat on it's face after a curve. there is no vacuum leak as i recall, which makes the issue sound as if it's absolutely valve train/event caused..... and of the possibilities of this, the most likely is indexed incorrectly, followed by ratio of rockers incorrect for head/chamber configuration, which is on an even plain with incorrect length of push rods, which is followed by mismatched (compared to port) lifters.... and then yet another issue that could be causing this which sounds absolutely nuts but should be said: oil available in the valley to charge the lifters... this is to say the lifters are correct, the push rods are correct, the rocker ratio is correct, but the oil pump volume of flow/pressure of flow is too little or too much.
you want oil available in the valley at all times... not just 'chilling out' in the sump... not so much that the sump runs dry and starves the pump, but not so little that the lifters lose charge when they're gettin' it purging and replacing oil in cycles that last microseconds.
of all the things you've done, and if those things were checked correctly, i'd be really surprised if one of the above isn't your huckleberry.
2007 300 EC, 350 Mags, B3's, Table Rock Lake, MO