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YJ RPM Question #928288 01/30/09 12:31 AM
Joined: Sep 2007
Posts: 24
Bishop, CA
RockRidge Offline OP
Need a Spot
My YJ will not rev over 3000 rpm. Any ideas as to why?

1990 YJ 4.2L Carb, 31x10.5.15, AX-15, Mostly Stock (The Red Sled)
2008 F-350 Superduty 4x4 350 HP/650 TQ (The Tow Beast)
Re: YJ RPM Question [Re: RockRidge] #928289 01/30/09 03:04 AM
Joined: Oct 2003
Posts: 7,768
Central Texas
BigJim Offline
Web Wheeler
Lots and lots of ideas... But first you need to tell us what is happening when it hits the rpm wall..
Does it spit and sputter?
Does the tail pipe whistle?
What gear are you in?
Which engine?
What gears and tires are on the thing?
Will it make more rpm in LOW gear?
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />

professional bovine relocation specialist
Re: YJ RPM Question [Re: BigJim] #928290 01/30/09 09:40 PM
Joined: Sep 2007
Posts: 24
Bishop, CA
RockRidge Offline OP
Need a Spot
Ok... Here Goes....

Does it spit and sputter? NO (Idle tubes have been drilled out to .032" also)
Does the tail pipe whistle? NO
What gear are you in? ALL GEARS (AX-15)
Which engine? 4.2L I6 W/CARTER BBD CARB with about 135K Total miles (Stock California Motor (was rebuilt/reman by PO about 1500 miles ago)
What gears and tires are on the thing? Stock 3.07 GEARS w/ 31 x 10.5 Tires
Will it make more rpm in LOW gear? If you mean in low range, I don't think so, But I haven't tried it yet.

It acts like it's hitting a rev limiter or something. It seems to rev fine up to 3K, but then won't go any higher.

(I just thought of this..What if the problem is the linkage not opening far enough? I should get SWMBO to watch the tach while I rev it from under the hood.)

Thanks for your help!
Ed

1990 YJ 4.2L Carb, 31x10.5.15, AX-15, Mostly Stock (The Red Sled)
2008 F-350 Superduty 4x4 350 HP/650 TQ (The Tow Beast)
Re: YJ RPM Question [Re: RockRidge] #928291 01/30/09 10:23 PM
Joined: Oct 2003
Posts: 7,768
Central Texas
BigJim Offline
Web Wheeler
Quote
Ok... Here Goes....

Does it spit and sputter? NO (Idle tubes have been drilled out to .032" also)
Does the tail pipe whistle? NO
What gear are you in? ALL GEARS (AX-15)
Which engine? 4.2L I6 W/CARTER BBD CARB with about 135K Total miles (Stock California Motor (was rebuilt/reman by PO about 1500 miles ago)
What gears and tires are on the thing? Stock 3.07 GEARS w/ 31 x 10.5 Tires
Will it make more rpm in LOW gear? If you mean in low range, I don't think so, But I haven't tried it yet.

It acts like it's hitting a rev limiter or something. It seems to rev fine up to 3K, but then won't go any higher.

(I just thought of this..What if the problem is the linkage not opening far enough? I should get SWMBO to watch the tach while I rev it from under the hood.)

Thanks for your help!
Ed


How long has this been happening?
My first guess would be the muffler or cat is partially stopped up.
I't hard to get an engine to top out at 3 grand that isn't running badly. If it was missing and chugging I'd be looking at the tune.. But since it just stops at 3 grand I'm thinking the exhaust...
With the idle tubes richening the mixture at ALL rpm, the excess fuel could be the problem with the cat..
Big JIm
<img src="/forums/images/graemlins/pfft.gif" alt="" />

professional bovine relocation specialist

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