Novak Conversions Jeep Wrangler YJ radiator

Weber 32/36 Rough Idle

jdsquire

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Aug 11, 2025
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4
Location
Texas
1987 YJ with new rebuilt 4.2L, automatic trans, nutter bypass, Weber 32/36 carb. After initial start up I set the timing at 11* and the Weber is set 2 rounds out on mixture screw and 1 1/2 rnds in on the idle per instructions. The engine always starts quickly and idles smoothly at 800-900 rpm. Once I put it in drive the rpm's drop to approx 600-700 and the idle is very rough, you can feel the vibration in the steering wheel, but it never sputters, backfires or dies. Once you accelerate it runs very smooth down the road. The Weber did sit for about a year during the rebuild and the only thing I did to it was clean it out, verify the float setting and I added sea foam to the gas tank. For trouble shooting purposes I added a fuel pressure gauge down stream of the filter. I have 4-4.5 psi at idle, when I increase the rpms the pressure will drop off to 2 psi. Not sure how it runs so well down the road at this pressure? What's next carb rebuild and new fuel pump?
 
Have you tried a cylinder compression test? I'm thinking at low idle with the throttle closed you may have one cylinder that will read low read low.

I don't know anything about Weber carbs or their adjustments.
 
4-4.5 is good for idle. the 2psi i think should be closer to 3.5? when did your last have a fuel filter change. have you checked the fuel pump, it could be going bad.
 
Novak Conversions Jeep Wrangler YJ radiator