Idle RPM - JeepForum.com
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post #1 of 6 Old 10-09-2020, 11:55 AM Thread Starter
HuckUSN
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Idle RPM

Ok so I have a 91 YJ with ATK 4.6L Stroker Engine and it idles around 1,000 RPMs when you start it and then goes up to 1,100-1,200 RPMs after it warms up. What RPM do those with a Stroker Engine set your idle at?


USN Jeep Club Hull #167
1991 Wrangler YJ
4.6L Stroker
Stock transmission, axles, and suspension
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post #2 of 6 Old 10-09-2020, 01:27 PM
Waternut
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If you need more than 700-800 rpms in anything short of some super high revving short stroke engine, you're compensating for something that's wrong. If the 4.0 and 2.5 can idle at those speeds, there is no reason why the 4.6 can't.


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post #3 of 6 Old 10-09-2020, 09:03 PM
Tarneg
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i have a 4.7 atk with a supercharger and it idles at the ~750 mark. did you happen to somehow get the warm idle circuit to be backwards and it raises rpm instead of lowering it ?
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post #4 of 6 Old 10-10-2020, 07:14 AM
fishadventure
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^^^whatchu talkin about?

Anyway, EFI wants a certain airflow speed to idle nice. A carb motor, 6 cyl, could potentially idle fine at 5-600rpm or a bit more. The CFM of a 4.7 probably needs 750-850 ymmv
High idle after warmup is almost always a vacuum leak or weeping injectors if everything else is right on OBD1. Probably 99% vacuum leak chance, less than 1% chance leaky injector(s).
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[size=3]Shackles & D-rings are different things.
Cranking IS turning over
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post #5 of 6 Old 10-10-2020, 08:10 AM
JeeperDon
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Mark is right. I too suspect you have a small vacuum leak. Extra air makes the computer add extra fuel, which raises the idle.
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'93 YJ, '02 GM 4.3V6, SOA, dual ARB's, 8.8+D30(WarnHubs), 4.88s, 35" BFG KM2s, AX15, NP231+4:1+SYE+2LO, York OBA, Warn M8000.
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post #6 of 6 Old 10-17-2020, 06:34 PM Thread Starter
HuckUSN
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Thanks for the reply, I'm just now getting around to checking out the leaking vacuum lines tomorrow. I'll let you know what I find out.

USN Jeep Club Hull #167
1991 Wrangler YJ
4.6L Stroker
Stock transmission, axles, and suspension
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