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Thread: 87 Horizon 2.2L 6520 Carb Will Not Idle

  1. #1
    Mitsu booster
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    87 Horizon 2.2L 6520 Carb Will Not Idle

    ive tried so many things i cant even describe.... if anyone would be willing to throw out ideas i can tell you if i have or havent tried it. quick rundown, checked vac lines and replaced bad. new plugs, wires, rotor and fuel filter. carb has been rebuilt.... its been sitting for 10 years, i DID NOT remove the old gas. it was a small amount so i added seafoam to stabilize it and then added fresh to it.

    still will not idle but runs fairly smooth at 2-3k rpm.

    any help would be great.. .thanks guys

  2. #2
    turbo addict
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    Re: 87 Horizon 2.2L 6520 Carb Will Not Idle

    Try putting in a bigger primary jet...might be just too lean to be happy. I am not a mechanic, but have had nearly everything happen to my cars. One night at the drag strip my car would not run unless I nailed the gas hard enough to open the mechanical secondary...after the race I got it home, pulled the top of the carb, looked at the jets and the primary one looked like a tiny rock was in it...ended up it was the but end of a bug!
    [SIZE=3][COLOR=#000000]47 Time NHRA/IHRA drag race champ-----84 Plymouth Horizon/1 of 84 HO equipped from the factory/1910 lbs, 2.5 with carb, nearly 315,000 miles-----04 SRT4/S2 with S3 turbo/12.17 @ 119/DOTs/93 Octane/SOLD-----2003 PT Cruiser GT, won a True Street class at the 2017 National Muscle Car Association World Street Finals-----2010 Toyota Prius/my delivery truck, 77.9 mpg best and NOT A PLUG IN, nearly 230,000 miles and way over 5600 miles per month! [/COLOR][/SIZE]

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    boostaholic Turbo Mopar Contributor
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    Re: 87 Horizon 2.2L 6520 Carb Will Not Idle

    Since it's ben sitting so long, it could be a number of things. I'd pull the top off the carb and check the jets for debris. Also check the air tubes for blockage. After that, the diaphram in the power valve may have dried out and gone bad. The old gas isn't helping either, even though you put Seafoam in it and dilluted it. 10 years sitting isn't good on anything in the fuel system.

    In fact, you may be better off getting a new rebuild kit and going back through the carb. No telling what has happened sitting that long.

    If it will run at 2K but not at idle, you have something wrong with the idle circuit, so I would start there. Blow out all the passages, if it's been rebuilt previously, hopefully they drilled out the plug for the idle adjustment screw. Take that out and blow air through it to make sure there is nothing in those tiny passages. Once you open the throttle blade slightly, the vacuum is gone from the idle slot, and the primary circuit takes over. That's why it runs off idle, but not at idle.

    Truthfully, I would can the 6520 and go with a new Weber. That carb was junk from the factory. Plus, you can get parts for the Weber, although most Weber parts will fit the 6520. I am lucky, my 2.2 came with the 5220, so I don't have to worry about all the electronic adjustment garbage on mine. I still plan on upgrading to the Weber next year though.
    Last edited by 83scamp; 07-29-2013 at 12:35 PM. Reason: added info

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    Re: 87 Horizon 2.2L 6520 Carb Will Not Idle

    my bad guys.. i shouldve been a bit more clear... im getting this car from my friends dad. he was driving it when this idle problem occurred. and it happened rather quick. i believe the carb was rebuilt previously, but i also just rebuilt it myself a few days ago. ive heard about this idle circuit before and im trying to find it. i also never messed with the idle mixture screw but since his dad said that it happened suddenly i was assuming it was that.

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    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: 87 Horizon 2.2L 6520 Carb Will Not Idle

    I am very new to working with carbs too, but i think 83scamp mostly covered it. It's a problem in the idle circuit and will PROBABLY be resolved by blowing out all the passageways of that circuit.

    I dont know for certain but i THINK the carb you have is very similar to the Weber 32/36 i just put on my CRX. IF that is true, then all the fuel being fed to the idle circuit and the transfer circuit comes through the main jets. So, since your engine runs at higher rpms obviously the main jets are not clogged. The idle circuit lets fuel into the carb through tiny holes below the throttle plate on the primary bore. When the throttle plate is closed, vacuum literally sucks fuel out of those tiny holes. They can be clogged. There's also an idle bleed screw which adjusts the flow rate of those tiny holes. If something is lodged in that needle and seat area it could reduce flow enough to affect idle. The transfer slots/openings will be just ABOVE the throttle plate when the throttle is completely closed. When the throttle is opened slightly, the air rushing past as high speeds generates a vacuum and sucks fuel out of those openings as well. It sounds like these ones are probably working but i would try to check all of them..

    Hopefully someone will check me and point out if my advice is totally irrelevant to a 6520.

    Dont push the red button.You hear me?

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    We Todd D dot D Turbo Mopar Staff sdac guy's Avatar
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    Re: 87 Horizon 2.2L 6520 Carb Will Not Idle

    Does your carb have the anti-dieseling solenoid on the rear (away from the engine)?

    It can be easily identified because it is about an inch or so in diameter, the top of it is a hard rubber, and there is a screw in the middle of it. My 85 GLH had this and it is important it is operating correctly for the engine to idle. It is there to keep the engine from running on after the key is turned off, by closing the air butterfly completely when the key is off.

    There is plunger on the bottom of it that contacts the carb linkage at idle (providing a ground to the solenoid). When the key is on, the solenoid is energized and the plunger extends a little to provide an idle setting. When the key is turned off the solenoid loses it's power and causes the carb butterfly to shut completely.

    If the wire to the plunger is broken, or if there is corrosion on either the linkage or the bottom of the plunger and good electrical contact can't be made, then the solenoid doesn't engage and the carb butterfly will close completely causing the engine to stall.

    Idle speed setting is adjusted by turning the screw on the top of the solenoid. But if turned so far that the linkage and butterfly are held open even when the solenoid is off, then it is possible, that the engine will run on, at times, when the key is turned off.

    Barry
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    turbo addict Turbo Mopar Contributor
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    Re: 87 Horizon 2.2L 6520 Carb Will Not Idle

    Quote Originally Posted by 83scamp View Post
    Truthfully, I would can the 6520 and go with a new Weber. That carb was junk from the factory. Plus, you can get parts for the Weber, although most Weber parts will fit the 6520. I am lucky, my 2.2 came with the 5220, so I don't have to worry about all the electronic adjustment garbage on mine. I still plan on upgrading to the Weber next year though.
    +1. The Weber 32/36 is bolt on except for a modification to the linkage arm that is needed. The Weber on my 2.2 ran much better and more consistently than the Holley 6520 ever did. I ran the 32/36 DFEV, which is $199 at Weber Carbs Direct.
    [B]Scott[/B] 86 GLHS #408 88 Shadow ES 92 Spirit R/T 04 SRT-4

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    Re: 87 Horizon 2.2L 6520 Carb Will Not Idle

    Quote Originally Posted by sdac guy View Post
    Does your carb have the anti-dieseling solenoid on the rear (away from the engine)?
    i DO have this solenoid you speak of. however i know for a fact that its wayyyyy out of adjustment because his dad messed with it trying to remedy the idle problem.

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    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: 87 Horizon 2.2L 6520 Carb Will Not Idle

    Sounds like a good place to start, then..

    Dont push the red button.You hear me?

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    Re: 87 Horizon 2.2L 6520 Carb Will Not Idle

    that makes sense... it does diesel. but only slightly. like it will shut off but it seems likes its a really hard shutoff. any idea what adjustment it should be at? like say i were to back it all the way off the linkage and clean the contacts (the wire is NOT broken) where should it be adjusted back to? and where the heeeeellllll is this idle circuit!? i cant find it, but i know its there.

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    boostaholic Turbo Mopar Contributor
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    Re: 87 Horizon 2.2L 6520 Carb Will Not Idle

    Quote Originally Posted by horizon_87_withneons View Post
    that makes sense... it does diesel. but only slightly. like it will shut off but it seems likes its a really hard shutoff. any idea what adjustment it should be at? like say i were to back it all the way off the linkage and clean the contacts (the wire is NOT broken) where should it be adjusted back to? and where the heeeeellllll is this idle circuit!? i cant find it, but i know its there.
    The adjustment is kind of a trial and error. Turn it in until the engine stays running, and then back it off to the desired idle speed. I agree with Vigo, I would start there. I forgot the 6520's had that "feature". If that doesn't get it idling, then you probably have something in the idle circuit.

    The idle circuit needle valve is on the front of the carb, basically under the electric choke pull off, at the base of the carb. It's a bear to get to with the carb on the engine. Most of them were set at the factory and the hole plugged. There is a proceedure in the FSM for drilling it out from underneath and using a small punch to drive out the plug. If it's been rebuilt, hopefully that is already done. I can post a picture, but not until later tonight. You need a really short screw driver(I believe flat blade?) to get between it and the valve cover.

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    Re: 87 Horizon 2.2L 6520 Carb Will Not Idle

    Quote Originally Posted by ScottD View Post
    +1. The Weber 32/36 is bolt on except for a modification to the linkage arm that is needed. The Weber on my 2.2 ran much better and more consistently than the Holley 6520 ever did. I ran the 32/36 DFEV, which is $199 at Weber Carbs Direct.
    I put the Weber 32/36 on old Matchbox when the NON-feedback Holley finally died. It ran the exact same AFTER I put the same jets in it that were in the old one. Note here...when I went from the tall block 2.5 to common block 2.5 I actually had to lean it out a bit! The gas mileage with the TB at 55mph was 25 and after the re-jetting on the CB it jumped to 29...NO other changes! Another thing I noticed...I had put a kill switch on the alternator and would pick up a bit over a tenth of a second on the TB, but on the CB it makes under .01 difference! I think the newer style alternator is less parasitic.
    [SIZE=3][COLOR=#000000]47 Time NHRA/IHRA drag race champ-----84 Plymouth Horizon/1 of 84 HO equipped from the factory/1910 lbs, 2.5 with carb, nearly 315,000 miles-----04 SRT4/S2 with S3 turbo/12.17 @ 119/DOTs/93 Octane/SOLD-----2003 PT Cruiser GT, won a True Street class at the 2017 National Muscle Car Association World Street Finals-----2010 Toyota Prius/my delivery truck, 77.9 mpg best and NOT A PLUG IN, nearly 230,000 miles and way over 5600 miles per month! [/COLOR][/SIZE]

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    Re: 87 Horizon 2.2L 6520 Carb Will Not Idle

    well thats the project for today.. im gonna pull the carb and get to that idle adjuster. i mustve done the 2nd rebuild on the carb because several rivets that required drilling were already taken care of. hopefully ill find the idle plug is drilled too but i doubt it. either way ill pull the carb to blast the hell outta that area. its one i didnt get to when i took it apart.

    also note that i got its started yesterday and played around. finding out that it runs about 2500 and if i manually hold my hands on the (i believe choke butterfly) on top and almost close it, it will idle.. albeit quite rough, but it will run. and the fumes are really strong so yea. but anyway, ill clean out that passage and tweak the idle solenoid and see where it gets me.

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    boostaholic Turbo Mopar Contributor
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    Re: 87 Horizon 2.2L 6520 Carb Will Not Idle

    Quote Originally Posted by horizon_87_withneons View Post
    well thats the project for today.. im gonna pull the carb and get to that idle adjuster. i mustve done the 2nd rebuild on the carb because several rivets that required drilling were already taken care of. hopefully ill find the idle plug is drilled too but i doubt it. either way ill pull the carb to blast the hell outta that area. its one i didnt get to when i took it apart.

    also note that i got its started yesterday and played around. finding out that it runs about 2500 and if i manually hold my hands on the (i believe choke butterfly) on top and almost close it, it will idle.. albeit quite rough, but it will run. and the fumes are really strong so yea. but anyway, ill clean out that passage and tweak the idle solenoid and see where it gets me.
    I say your idle passage is plugged. By closing the choke, you are forcing a vacuum signal on the primary and causing it to discharge fuel. It will make it run pig rich, which is why you have the strong smell. I think you have your answer.

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    Re: 87 Horizon 2.2L 6520 Carb Will Not Idle

    so the top one is the one i drilled... it was the only one with a plug..... (7 oclock in location FROM the bottom choke mounting screw) i know realize that was completely wrong... after i realized this WASNT the idle thing... i looked at the bottom one.... which has no idle adjusting screw in it.... i didnt bother looking at it because it was just a hole straight into the carb.. soooooo wtf....

    so thaaaaaats where the huge vacuum leak is coming from and why it wasnt leaking... the gas was being sucked in by the vacuum and also sucking air... wow... thats why it idled normal when i closed the top of the choke. all the air going in the engine was coming from that missing screw.... wow.. just wow.

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    boostaholic Turbo Mopar Contributor
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    Re: 87 Horizon 2.2L 6520 Carb Will Not Idle

    Looks like you found your problem. That would also explain the sudden change in idle you described. When the needle fell out, it all went South. Good luck finding a replacement. Although, a Weber replacement might fit. Looks like the Weber #'s you need are:

    64750.028 needle
    47600.007 spring
    41565.008 gasket(o-ring)

    You can give them a shot and see if they will work.

  17. #17
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    Re: 87 Horizon 2.2L 6520 Carb Will Not Idle

    well his dad had a spare horizon that had a head gasket go bad.. were robbing parts from it. so i pulled the needle and spring but no oring. so that may still be where my problems are. cause its idling somewhat better. but the missing oring combined with all the adjusting screws (idle, throttle and diesel solenoid) being outta wack, and crappy gas, ( i did add some fresh) im sure thats all why its still being a pain.

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    boostaholic Turbo Mopar Contributor
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    Re: 87 Horizon 2.2L 6520 Carb Will Not Idle

    O-rings are pretty easy to come by usually. Try your local Ace hardware. They usually have a pretty decent selection.

  19. #19
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    Re: 87 Horizon 2.2L 6520 Carb Will Not Idle

    where does the oring go? between spring and screw head?

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    boostaholic Turbo Mopar Contributor
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    Re: 87 Horizon 2.2L 6520 Carb Will Not Idle

    Usually there is a groove in the screw head that it goes in. But it could go under the head. The spring would keep it in place. I'll have to check my FSM.

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