Redhook98

I read through a few topics on here about gapping the plugs at .050 on a 496. Ray stated that the 496 seems to run best at that plug gap. I ran my 2003 496 HO in my Velocity all weekend with good results with them gapped at .060. I pulled the plugs out and regapped them to .050 this afternoon. I started the boat up in the driveway on the flushing unit and the idle does not seem as steady as when they were gapped at .060. It hunts a little between 620 and 660 after being warmed up. Is this normal? The plugs are he AC Delco 41-983's. Also getting an intermittent crank sensor alarm on the Rinda. Have not had any issues with this though... ??? Could the slight misfire from the arcing wire do this?

The reason I pulled them all was to check the gap and examine the wires. I had one arcing a little and wanted to tape it up. All the plugs showed good burn patterns and were white-whitish gray in color. Plugs and wires look new.

Raylar

That .010" plug gap difference should not affect the way the engine runs at idle or cold or warm. Try and be careful not to damage the plug wire ends pulling them on and off for plug work and do not pressure gap these fine center electrode platinum tipped plugs they damage very easily that way.
When I say pressure gap for those readers who might not know what that means, some of the simple spark plug gapping tools have you push a circular tapered tool in between the center electrode and the body electrode, this can put to much pressure on the fine center platinum tipped electrode and damage it and sometimes cause it to fail in the insulator and ruin a perfectly good sparkplug. Use a tool that bends the body electrode up and down and carefully meaure gap with a round wire gap tool if you can.

I guess I would be interested to see if you carefully regap them to .060" and the problem disappears then I will have to do some research here on my end as we have not seen these issues from a .050" gap.

If there is enough access you can actualy remove a plug wire one wire at a time while the engine is running and see if sounds and rpms change. If you have a bad plug or plug wire the cyllinder not firing properly or at all will generally show no change in rpm or sound so you can sometimes isolate a non-firing cylinder this way. Just be careful, the hit off one of these seperate coil per cylinder coils can really bite and the spark can jump a 1"-2" gap sometimes!

Best Regards,
Ray @ Raylar

Redhook98

Thanks Ray. I was hoping you would see this post. I gapped them with the wire gauge and gently bent the body electrode each time a tweek was needed.

I tried disabling each cylinder one at a time using my Scan Tool (intentional misfire). I did not notice much difference. It's a loud SOB as my riser-to-tips length is only appx 20 inches. I am thinking the IAC compensates right away and brings up the RPM? The instructions say to do that check above 1500 RPM and under a load. I was in my driveway.

The IAC values (on the Scan Tool) fluctuate quite a bit as well. Is that normal? I realize those things are always on the move and working.

Instead of regapping the plugs, my next step may be to switch over to the Iridium plugs and gap those at .050. Have you had much luck with the NGK Iridiums?

Sydwayz

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Subscribed.

I run the NGKs in mine, and have since new. I can't remember what I gapped them at 3 years ago!

Raylar

The Iac counts will fluctuate a lot especially at idle when the engine is hunting a lot trying to find a stable idle. the engine after warm up should idle about 650 rpms + - 25-30rpms.

The NGK Iridium plugs would be fine but I am not sure they will fix a miss problem, especially if its from plug wire contacts, etc.
If you remove the plugs fairly quickly after running you should be able to see a wet plug thats not firing properly and that may pinpoint the miss is you have one.

Best Regards,
ray @ Raylar