Okay, maybe I'm missing it, but I cannot find what the gaps are supposed to be in the FSM for an 2005 4.0 liter. Please help me out!
.035 for the older TJs with a distributor cap, .04 for those with the coil rail since it generates a bit hotter spark for each spark plug.
So which is more likely incorrect, an underhood decal or the factory service manual? Does it really matter?'04 Sport under hood decal . . . . 0.035
So which is more likely incorrect, an underhood decal or the factory service manual? Does it really matter?
The reason for bigger .04 gap per the FSM in newer TJ's with the coil pack is the hotter voltage at the plugs when compared to the older ignition coil system.
I'd say that the "hotter" ignition system can drive gaps larger than .040. When I recently swapped plugs on my new to me TJ the originals I took out were over .080 and it was running fine. It runs better now but there wasn't any noticeable issues with it before either.So which is more likely incorrect, an underhood decal or the factory service manual? Does it really matter?
The reason for bigger .04 gap per the FSM in newer TJs with the coil pack is the hotter voltage at the plugs when compared to the older ignition coil system.
The Fram/Autolite technical trainer I know, Jay Buckley, just replied back to a text I sent him last night seeking his insight. He taught it as the coil-on-plug design puts out significantly a higher voltage so the gap can be opened up more to produce a hotter spark which improves combustion which helps to lower emissions. That's why the recommended gap in the Factory Service Manual went from .035 to .040.I'd say that the "hotter" ignition system can drive gaps larger than .040. When I recently swapped plugs on my new to me TJ the originals I took out were over .080 and it was running fine. It runs better now but there wasn't any noticeable issues with it before either.
I don't doubt this. I wonder if I should pull the plugs I just put in and gap them up to .040. Maybe I'll do it after the first tank of gas at .035 and see if there is a difference in efficiency that is noticeable.The Fram/Autolite technical trainer I know, Jay Buckley, just replied back to a text I sent him last night seeking his insight. He taught it as the coil-on-plug design puts out significantly a higher voltage so the gap can be opened up more to produce a hotter spark which improves combustion which helps to lower emissions. That's why the recommended gap in the Factory Service Manual went from .035 to .040.
I personally wouldn't spend any time pulling existing plugs and regapping them .005 wider. I'd only do that when installing new plugs.I don't doubt this. I wonder if I should pull the plugs I just put in and gap them up to .040. Maybe I'll do it after the first tank of gas at .035 and see if there is a difference in efficiency that is noticeable.
Thanks for the clarification.