Down on power

[RickR90s]

I have a 2001 engine (5.7L HO) that ran fine all last year. I winterized it and this spring, it starts fine, but has a rough idle and will not plane out without full throttle. Top speed is only 39mph, and 4000 rpm. I suspected bad gas so that was drained and 10 gallons of fresh added. No change.
I then pulled the plugs to discover cylinders 2, 4 were black so all were replaced. No change.
I pulled the fuel filter (fuel control cell) and it's clean with no water present in the cartridge. No change.
I hooked up my timing light and I see about 10 degrees advance at idle. (no marker plate like on old Detroit V8's) but I can see the mark on the harmonic balancer is ahead of the little mark on the water pump cover. Interestingly, when rpm's are raised to about 2000 rpm, there's very little advance, like maybe a couple of degrees.
I pulled the distributor cap and cleaned the little bit of debris on the connections but no change again. There is a donut type mechanism that appears to rotate, to change when the hall effect is triggered (and spark) is delivered, but it sort of stays in one place, with no mechanical connection to anything that I can see.
So I'm wondering if I have an advance issue and if so, how does the system work to ascertain what needs replacing.

Thanks so much,
RickR90s

[Infinity]

Is there also an inline fuel filter you want to check/change? I know a lot of the older models had an inline filter under floor.
Many times on cap and rotor....there will be an issue that is not easily seen, so may be a good idea to replace. How do your plug wires look?
Tough to start throwing money at it, but I would start with replacing the "maintenance items" like cap and rotor since they are not that expensive....(have you checked the plugs since replacing to see how they look?). Make sure plug wires are not split. Perhaps check compression to be sure no issues there.
Is this a carb boat? Possible it needs a re-build/good clean (did ethenol fuel sit in there over layup) or perhaps IAC is malfunctioning due to rough idle.
Make sure you do not have an inline fuel filter that is clogging and perhaps check the fuel pump.... I had an older boat about 5yrs ago that I replaced all the fuel lines since ethenol can degrade them.....it ended up being a combination if issues for me. (carb re-build due to prior owner using ethenol fuel, fuel pickup replaced and ball in anti-siphon was sticking so that was removed, drained all old gas and replaced, timing was off and replaced the cap, rotor and plugs)

I am no mechanic, just a DIY guy that likes to figure out my own issues when possible, but these are the things I would look at first since it ran good for you last year. Hopefully some people with more knowledge and experience than me will chime in too.

[RickR90s]

I love it when a plan comes together.

This morning it hit me. Why would plugs 2 and 4 be black when all the others are pristine? Checking the spark plugs wires and knowing by heart the standard small block Chevy firing pattern since I was a kid (18436572), I quickly found plug wires 2 and 4 were swapped.

Please don't laugh. God love a small block Chevy though.

All 330 horses are back, and I'm going skiing, ba-beeeee!!!!!!

[DealsGapCobra]

That is Great news! It may be a silly fault but an easy fix.


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[charlesml3]

I quickly found plug wires 2 and 4 were swapped.

How did this happen? I wouldn't think that someone doing a winterization would be unplugging spark plug wires.

-Charles

[RickR90s]

Charles, I looked at my notes from winterizing. I usually fog the motor through the throttle body, shut it off and then replace the plugs. I must have switched the two wires.

[charlesml3]

OK, gotcha. Well thanks for detailing it here. If someone else makes this same mistake hopefully they'll find this thread and avoid a trip to a mechanic.

-Charles