Hi.. I have the Haynes manual but I trust you guys more than some manual. Just because it's written and published, doesn't make it true.
2002 4.0 - gotcha. Idle specs aren't normally provided, as there is no adjustment possible. My '05 TJL ticks over about 550 idle when warm, so you're in the ballpark. If you think idle quality is an issue, clean the throttle body with some TB spray and a soft toothbrush & a soft rag.
Higher oil pressures at cold startup is normal. Very high pressure isn't. Higher pressures mean flow is impeded, and this is not good. The K&N might have more restrictive pleating. If you stick to the OEM viscosity spec for the COLDEST startup conditions, it shouldn't be a problem.
Also, I wouldn't trust Haynes for much of anything.
Thanks - Mine is around 550 rpm as well. The oil pressure isn't very high, but its high compared to what I'm used to. The K&N is a higher flowing filter and traps more dirt. They run about 17.99 at Canadian Tire. I just switched over to synthetic oil my last oil change.
"Higher flowing" and "traps more dirt" are usually mutually exclusive. Have you done a filtration analysis or is that the K&N claim?
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