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Unread 01-22-2013, 05:28 PM   #1
198839
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Carter BBD stalling. Works if wire plug pulled.

1983 258 CJ7 stock carter BBD with emission wiring plug. If I pull this plug out/off the back of the carb the jeep runs fine. With it plugged in the jeep wants to stall at idle like the ignition switch is being turned off. Racing the engine will keep it running but as rpm drops towards idle it shuts off unless the stepping on Gas peddle catches it. Oh and it's intermittent but will pretty consistently stalls if the plug is installed into the back of the carb. With the plug/ wires pulled out jeep runs great. I'd leave it out but it will not pass CA smog next year. Any ideas? ECU?

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Unread 01-22-2013, 05:37 PM   #2
86cj74.2L
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Look down the throat of the carb and tell where the needle is at when its about to stall.

That stepper should not be operating until the engine reaches 130 degrees and the airfilter housing is above 60 degrees.
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Unread 01-22-2013, 06:55 PM   #3
198839
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The motor starts stalling after it warms up. The needle moves around when I work the throttle. I don't think it stops in any consistent spot by I will check it out. It stalls like it is losing ignition not from a fuel problem. The stock tac needle drops dead as its trying to stall from about 2000 rpm. If I step on the gas it will revive it until the rpm of the motor drops again.
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Unread 01-22-2013, 07:21 PM   #4
86cj74.2L
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Quote:
Originally Posted by 198839
The motor starts stalling after it warms up. The needle moves around when I work the throttle. I don't think it stops in any consistent spot by I will check it out. It stalls like it is losing ignition not from a fuel problem. The stock tac needle drops dead as its trying to stall from about 2000 rpm. If I step on the gas it will revive it until the rpm of the motor drops again.
Where is the needle when its not moving around? All the way front or all the way back?

Go here and start reading......

http://home.sprynet.com/~dale02/list.htm

Print out every page.
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Unread 01-22-2013, 08:52 PM   #5
198839
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I've seen this info before, thanks, it's great stuff! What's got me stumped is the needle is moving around so the computer, the stepper motor and the o2 sensor seem to be doing what they are suppose to, but something is happening that kills the ignition when the main three items are allowed to function. I was wondering if anyone had this type of problem before and fixed it. To me iti seems something in the stepper motor/computer circuit is not right. That's why I'm thinking the MCU might be bad, but I'd feel better about buying one if someone else had a similar problem. I'll be able to check the position of the pin when it stalls in the AM.
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Unread 01-22-2013, 09:27 PM   #6
86cj74.2L
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So it constantly moves just sometimes the motor stalls?

Look down the carb throat and look to see if their is fuel dripping out of the brass tubes inside the Venturi's.

Never heard that problem before. But your mcu controls both spark and mixture so it could be going bad........
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Unread 01-22-2013, 10:03 PM   #7
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The 1984 FSM has a whole section on the system. Have you found a copy?
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Unread 01-23-2013, 02:52 AM   #8
John Strenk
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Seems like you have a bad vacuum leak that the computer can't keep up with. Dont forget these cars probably only had a 5 or 10 year life expectancy designed into them. Old, rotted, dried up rubber hoses causes a mess of problems with the sensors and carbs. There are two control circuits in the BBD, the original mechanical one that is totaly controlled by engine vacuum to keep the mixture right and the electronic control that fine tunes the carb. If the engine has leaking vacuum hoses athen the carb's mechanical mixture control will be way out of control and the poor electronic mixture control swigs wildly trying to keep it under control.

You absolutely have to make sure there are no vacuum leaks on the engine. I would just start replacing all the hoses in the engine compartment. I have no way to insure a vacuum hose is good unless it has just been replaced. Just pick up 20' of vacuum hose at the auto parts store. Bring in one to get the right size. Replace them one at a time.

You could also have a flaky computer that could be caused by a poor ground connection or Bad sensors. Or both. Could also be a problem with the knock sensor that has dried up and thinks every cylinder fire is a knock. When the knock sensor sends a knock signal the timing is backed off this also messes with the engine vacuum and starts snowballing problems.

Don't forget the distributor firing is controlled by the computer and if the computer quits, so does the engine.

So buy a vacuum gauge, they are cheap and start by checking the vacuum system. Check your grounds, engine to from, engine to body, etc, etc. Then move up to the more expensive stuff. Maybe you could swap out your computer with someone elses.

83 was an odd year for CJ computers. 84 on everything was controlled but in 82 or 83, I think the computer just controlled the mixture.

Is your computer mounted on the driver fender?
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Unread 01-23-2013, 06:42 AM   #9
bkeese
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The first place to check for a vacuum leak is the throttle shaft. Look for movement in the shaft, especially at 1/2 throttle. I'll bet there is plenty. If so the throttle shaft needs to be bushed. Just about everyone I've ever looked at needs to be bushed, including the ones that come from the big re-builders at a pretty $300 price tag.
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Unread 01-23-2013, 04:38 PM   #10
198839
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First off thanks to everyone. I do appreciate it. Ive owned this jeep for over 25 years now and been using this forum off and on and it's great! My jeeps not a daily driver but being in CA i have to still pass smog every two years.

The ECU/MCU is up under the dash aside the heater core box/vent system. This AM I looked at he ECU and pulled pushed on all the wires going into it. I started the jeep and now it's not stalling?! This is what's so frustrating with this problem it's intermittent. The needle in the carb is moving for and aft when I rev the engine so I, guessing its working as it is suppose to. It passed smog last year. The other weird thing is it seems to wants to stall/shut off more often at idle after its been warmed up/driven then shut off and restarted. Like restarting the engine aggravates some component into its failure mode. Today I drove it shut it off restarted it several times and could not get it to stall/shut off. Crazy problem. It is possible but I think unlikely that messing with the wires on the ECU fixed a loose wire but I doubt it.

It's a great idea to change all vacuum hoses. Thanks again for everyone's help.
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Unread 01-23-2013, 04:58 PM   #11
198839
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Another question. When it does stall at idle it seems to happen when after I rev the engine while standing by the fender listening to the engine it will idle down then it stops foe a second at about 1000 rpm ill hear a small click somewhere near the carb then the rpm will drop to 650/700. When that click happens is when the engine shuts off. So whatever is allowing the rpm to drop to its idle setting is part of what is shutting off the motor. Like I said TODAY the jeep is not broken at all and is running fine. The click happens and the rpm drops to about 700 and the engine is idling fine. as I said its a crazy problem.
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Unread 01-24-2013, 03:30 AM   #12
John Strenk
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I think that "Click" is the Sol-Vac operating.
Look on the carb for this:


You can read up on it here:

http://home.sprynet.com/~dale02/solvac.htm
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Unread 01-24-2013, 05:53 AM   #13
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I think he needs to reset his lean best idle when the sol-vac puts it down to low idle. As a start.
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Unread 01-24-2013, 08:31 AM   #14
198839
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The Sol Vac lost it's ability to hold vacuum so I disconnected it a few years ago. It's still on the carb but not doing anything. when it worked it would hold the idle a little bit higher for a few seconds when coming off I high RPM for emissions I guess.

The click is coming from a zone right behind and towards the passenger side of the carb but it's really hard to hear exactly where it is coming from. I've tried several times to isolate it disconecting this and that (because it is associated with the shut off proble) but with no luck. I think it's a normal sound that's always been there but now I notice it cause it's associated with shut off/stalling issue. I'm thinking It's got to be one of the emission components activating but I have no idea which one.

It's a brain tease no doubt. Especially since yesterday the "shut off/stalling" problem disappeared, again. I'll start it today and see what happens. Adventures in jeep ownership, right? It's all good. The jeep is just a toy now for me and the kids to take to the beach and I can make it work if it acts up by pulling the plug off the carbs stepper motor. It's the emission test monster stalking me that has me worried. I guess I could move to Texas!
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Unread 01-24-2013, 11:39 AM   #15
86cj74.2L
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Do you have a row of solenoids on top of the valve cover?

Three of them? I think one is a canister purge.
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