Engine won’t idle back down

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NorthMN
Posts: 28
Joined: Sun Apr 11, 2021 6:37 pm

Engine won’t idle back down

Post by NorthMN »

I’ve got my 1980 Jeep Cherokee Chief at my mechanic. It got a new Edelbrock intake, and a 4 barrel Edelbrock AVS2 carb. I got the following message and I’m hoping someone can help me out. “ Your heater core is leaking. And i cant get it to idle down, the power steering pump is getting so hot it blistered my hand and its the 2nd pump. So there might be something wrong with the gear box”. Prior to the new carb the engine would idle down fine. Hoping that maybe someone can offer some advice so it can point him in the right direction. Any ideas?
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dodgerammit
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Location: Middle TN

Re: Engine won’t idle back down

Post by dodgerammit »

Umm. There's lots of things that can cause idle issues with a carb, but all are relatively simple. Might find a mechanic that knows what they're doing.

Sorry to be blunt, but if they can't troubleshoot an idle issue on a carbureted motor, they're not much of a mechanic.
84 Grand Waggy-Radio Flyer (Garnet Red/3M Ebony Metallic woodgrain, with honey interior) AMC 360 :cry: 2004 4.8LS/Advance Adapter/727/242 D44/AMC20 Serehill tailgate and headlight harnesses :fsj: Ongoing thread-viewtopic.php?t=11897

92 Wrangler Islander 4.0/32RH/231 D30/D35 RHD

will e
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Joined: Sat Aug 18, 2012 8:21 am

Re: Engine won’t idle back down

Post by will e »

I am going to assume it has an electric choke. I looked up avs2 carbs and it appears there are several models, do you know the model number for your carb?

If it has an electric choke the first thing to confirm is that the choke is operating correctly. The carb will high idle until the choke opens up, this normally takes a couple of minutes. There has to be electric current to the choke while the engine is running. Verifying this is easy with a volt meter or observing the carb for the first few minutes of operation as the choke plate opens.

The next most likely candidate is a vacuum leak. There are several ways to trouble shoot a vacuum leak. To be certain I would plug every vacuum port at the source. If the engine still idles high then spray water or carb cleaner around the base of the carb, if the engine speed slows down a bit then the carb isn't sealed correctly on the intake.

This assumes "Prior to the new carb the engine would idle down time" and that no other work like a new ignition, timing chain, etc, has been performed.

There are a lot of mechanics who are not going to be familiar with carbs. Is this a local shop? How old is your mechanic?
81 Waggy 'WILL E' Retired
82 Cherokee WT - SOA/SF/high steer/Alcan springs/agr box/Borgeson steering shaft/AMC 401/performer/holley TA/HEI/BeCool/727/ALTAS (2.0/2.72/5.44)/D60 Snofighter(Yukon Zip,hubs,stubs,4.56)/14 Bolt (FF,BF shave, Discs, ARB,Artec Truss)/MTR 37X12.5/Corbeau XRS Baja & 5 point retractable harness/Hella Aux lights/tuffy console/killer32 sliders/Evil Twin bumpers, rack and roll cage/WARN 8000/TT Fabworks steering brace/dual batts/custom TC skid plate/ARB fridge

letank
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Location: SF bay area

Re: Engine won’t idle back down

Post by letank »

for the PS, remove the belt.

for the heater core, bypass it.

and for the carb, take it to someone else.

Otherwise, makes sure that the idle stop screw is not holding up the throttle plates partially opened, then you can reduce the timing if too high, or lean the idle mixture
Last edited by letank on Fri Jan 28, 2022 5:10 pm, edited 1 time in total.
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74 wag (349 Kmiles... parked, next step is a rust free body)
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akguy09
Posts: 301
Joined: Mon Aug 30, 2021 6:11 am
Location: Ellicott, Colorado

Re: Engine won’t idle back down

Post by akguy09 »

I feel bad for the OP, this mechanic sounds like a parts replacer
1979 Jeep J-10 304/T-18
2017 Jeep JK 2DR
2021 PowerWagon

Topic author
NorthMN
Posts: 28
Joined: Sun Apr 11, 2021 6:37 pm

Re: Engine won’t idle back down

Post by NorthMN »

Thanks everyone for the advice I really appreciate it. I just moved and was pressed to find a mechanic since I was having some issues. Most mechanics where I moved to won’t touch a carburetor (was an AVS2 W/Electric choke part #1906) with a 10ft pole. A new valley pan and Edelbrock performer intake were put on. Seems that a vaccum leak is the root of the idle problem. Intake is coming off this weekend to find and fix the vaccum leak.

will e
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Joined: Sat Aug 18, 2012 8:21 am

Re: Engine won’t idle back down

Post by will e »

On my Ford Clevland engine the aftermarket intake had a runner that was lower than the stock runner. It wasn't obvious and it took a couple of tries putting on the manifold with new valley pan gaskets before I figured out the problem. I would put the valley pan into place and then set the intake on top and it would push it down just a touch but it was far enough to cause vacuum leaks.

I am not claiming this is your problem but if you do pull the intake, check that the pan fits.

Before pulling the intake you should be able to spray water around the intake runners and if the RPM varies then you know the source of your vacuum leak.
81 Waggy 'WILL E' Retired
82 Cherokee WT - SOA/SF/high steer/Alcan springs/agr box/Borgeson steering shaft/AMC 401/performer/holley TA/HEI/BeCool/727/ALTAS (2.0/2.72/5.44)/D60 Snofighter(Yukon Zip,hubs,stubs,4.56)/14 Bolt (FF,BF shave, Discs, ARB,Artec Truss)/MTR 37X12.5/Corbeau XRS Baja & 5 point retractable harness/Hella Aux lights/tuffy console/killer32 sliders/Evil Twin bumpers, rack and roll cage/WARN 8000/TT Fabworks steering brace/dual batts/custom TC skid plate/ARB fridge
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dodgerammit
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Joined: Wed Jan 11, 2017 11:20 pm
Location: Middle TN

Re: Engine won’t idle back down

Post by dodgerammit »

NorthMN wrote: Sat Jan 29, 2022 8:56 am Thanks everyone for the advice I really appreciate it. I just moved and was pressed to find a mechanic since I was having some issues. Most mechanics where I moved to won’t touch a carburetor (was an AVS2 W/Electric choke part #1906) with a 10ft pole. A new valley pan and Edelbrock performer intake were put on. Seems that a vaccum leak is the root of the idle problem. Intake is coming off this weekend to find and fix the vaccum leak.
AMC specific aftermarket intakes are notorious for requiring LOTS of sealer at the front/rear of the intake instead of the gaskets. So, the sides get the gaskets, while the front and rear get liberal amounts of RTV.
84 Grand Waggy-Radio Flyer (Garnet Red/3M Ebony Metallic woodgrain, with honey interior) AMC 360 :cry: 2004 4.8LS/Advance Adapter/727/242 D44/AMC20 Serehill tailgate and headlight harnesses :fsj: Ongoing thread-viewtopic.php?t=11897

92 Wrangler Islander 4.0/32RH/231 D30/D35 RHD
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