Plug Change

[rune]

Well...as part of getting this beast ready to tune, I've gone through and started doing some maintenance on her. An initial scan showed quite a bit of Knock Retard occurring all over the place, but especially higher RPMs. Started running higher quality fuel as well as getting fuel injector cleaner through her to get the fuel system clean. Currently at 89, but next time jumping to 91. Suspect Ethanol may be causing some of this. Decided to replace the plugs today as well. Decided to stick with good old copper plugs for the time being and regapped to .045. Couldn't believe how bad the old ones were. Prolly original and at 74k were covered in deposits. Took the truck out for another run and can definitely see an improvement, however the smaller gap may have introduced some pre det. Noticing that at low timing advance <20 degrees the truck is running around 5 degrees of KR. Above 20....no problem. It's not consistent, but I can re-create it. Otherwise, only seeing KR at high rpm acceleration. Still in the 4-5degree range, and it's making me wonder if there is a fueling pump/filter issue. Otherwise....she pulls like a freight train. Really can't wait to start tuning. If anyone has any input on fuel issues with these motors please let me know. Service records show the pump has already been replaced once.

[txab]

What year, engine, etc....

 

For fuel issues, check fuel pump pressure.

 

You may have a upper cylinder carbon problem

[rune]

Sorry. Forgot this is all 2500s. Its an 06 with the 8.1.

[markw8]

Can I ask why you would use a copper plug and gap that the engine wasn't designed for? Especially when Iridium plugs are virtually trouble free to 100k plus.

 

Mark

[rune]

On the subject of Spark Plug type... I'll just post this article. It summarizes everything pretty well. http://www.carsdirect.com/car-repair/copper-spark-plugs-vs-iridium-and-platinum-understand-for-top-performance. My reasons on top of this include the fact that these motors are know for burning oil. Burning oil results in a build up on the plug. On plats/iridiums the tip is small and tapered and this buildup will begin to hinder the spark performance. Given the larger surface tip of a copper plug, this helps them last a little longer under the same conditions. Also.... I have yet to find a plat/iridium that lasts as long as they claim. I would rather change plugs every 30k, and maintain performance, and spend 2$ a plug, than spend 7$ a plug and replace every 50-60k. The biggest reason for going the whole plat/iridium route is to keep from changing your plugs frequently.

 

With regards to re-gapping to the .045 spec, I have found on plenty of forums that this is a recommended mod on the 8.1L. In all honesty it's just an old mechanical trick to introduce additional timing. Plus, from watching my scanner the truck is commanding additional timing after doing this. Whether this is from just new plugs, or a more consistent burn cycle, I can't tell yet.