3.6 Factory Idle

72Blazer

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What’s everyone seeing? Seeing about 1100-1200 at idle. Could have sworn I saw it lower than that this morning. Search didn’t bring much up.



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nerubi

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Initial cold start has around 1100 idle then goes down to around 600.
 

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Idle drops to between 600-700 when warmed up. What do your coolant temp and oil pressure readings say?
 

cosine

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first start i'm at 1100 / 1200. then its drop to 600 / 800 in 3 or so mins.
 
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72Blazer

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Mine was already warmed up. I ran it hard to merge on the highway when I noticed higher RPMs at cruising speed. When I stopped at an intersection I noticed the higher (in gear) RPM. Have not checked my oil pressure or coolant temp.
 
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Went back to check on it after shutting it off for about 25 minutes. Oil and Coolant temps seemed fine. Idle was back down to 700ish. Oil looks like it was overfilled with the 6 quart crap. It usually sits In the garage but trying to log some miles before our vacation next month. I’ll see if it’ll repeat the high idle.
 

rubileon

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Mine was already warmed up. I ran it hard to merge on the highway when I noticed higher RPMs at cruising speed. When I stopped at an intersection I noticed the higher (in gear) RPM. Have not checked my oil pressure or coolant temp.
For how long did it stay like that? Did your start stop work? Also do you have BSG?
 
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72Blazer

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For how long did it stay like that? Did your start stop work? Also do you have BSG?
I’d say about 45 minutes with a mix of staying parked but on, highway driving, and city driving. At one point, I attempted to turn it off/ on with no change. I had my ESS turned off. BSG??
 

rubileon

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I’d say about 45 minutes with a mix of staying parked but on, highway driving, and city driving. At one point, I attempted to turn it off/ on with no change. I had my ESS turned off. BSG??
Maybe the catalytic converters or the O2 sensors are acting up. I'd record a video while it's in P and show a dealership. If you're not confident about them believing you, get a third party mechanic to diagnose it in a non-invasive way (so you don't get warranty voided).

BSG: https://www.jlwranglerforums.com/forum/threads/bsg-vs-ess-a-simple-explanation-please.1352/
 

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Main thing I see, this transmission HATES 8th gear. This is a Rubi with stock tires. Maybe the Jeep didn't ever go into 8th gear, there is a big difference between 7th and 8th on these things. Do you have the gear indicator on?

On initial warm up, yes the RPM's are through the roof. I guess to get the engine up to operating temp faster. Once it gets there the RPM's drop. Like everyone else is saying in this thread.
 
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It went back to normal today.

Driving conditions yesterday included the HikeIt on Sport Mode running 37s with stock gearing. It’s possible the transmission was trying to learn the shift points as I ran it hard? But I agree 8th is pretty much useless. I dropped it down to cruise mode today and had no issues. But I also babied it on the way to work. I will keep an eye on it and report back.
 

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Mine starts at about 1100 and drops to 600-650 after a minute or less. It says there from then on, regardless of A/C or how I drive. (3.6 8-speed 2018)
 

TEXGOAT

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37s make 7th into 8th. Mine stays in 8th a lot, but not all the time, on the highway. I have Sahara wheels/stock tires on a JLU. They're about 1" taller than the stock 17s. Engine RPM is way down in 8th. I don't think running in 7th will do any harm. Figure the engine RPM at 60 MPH in 8th with stock wheels/tires and compare it to what you are doing at 60 MPH in 7th with your tires. I doubt there's much difference, and I'd expect that any MPG penaltyrelated to your oversize tires has more to do with increased road friction and aero drag than running in 7th.
 

TEXGOAT

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I'd think a 3.6 8 speed would spend a lot of time in 5th, 6th, 7th, and 8th on most secondary roads in rolling or hilly country. Pushing into a headwind on the interstate would keep you out of 8th a lot, too.
 
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Yes. All things I’ve experienced and have come to accept with the 37s. Even on the stock 33s I’d sometimes have trouble maintaining 8th so really I haven’t noticed much of a difference. My RPMs at idle and speed seemed to be back to normal today. Cruising at 75 I’m at about 2400 RPM in 7th. 8th likes to engage and stay engaged at 65 or 85+.
 



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