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Unread 03-25-2013, 05:50 PM   #1
SoothSayer
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Curb Idle near 2000rpm

Hey All. New to the forum and jeeps in general. I'm a total newb so bear with me. I have an 82 CJ7 w/ BBD. My jeep with choke plate fully open,fast idle not engaged at all, curb idle screw completely backed out still idles around 2000 rpm. I've pulled the spider web vacuum hose setup and replaced with a K&N filter sitting right on top of carb. Also new hose between dist & carb, carb & EGR, PCV valve & hose new. I pulled carb, scrubbed it clean, rebuild w all new gaskets and cleaned all surfaces. Followed FSM for float, vacuum piston, and accelerator pump adjustments. Have adjusted dist timing as well, not sure the setting though. Installed manual choke as well. Stepper motor is plugged in and pins all the way in.

From what I've read this could be the mixture is way too lean. I've tripled checked for vacuum leaks, solid seating of carb to mani, tb to main body, etc.

Side note i've noticed my borla exhaust headers light up red hot after 10 min or so of idling in garage, this could have been happening for a while and I didn't notice it. I'm guessing this is a result of the high rpms or a clogged cat, or both. I'm thinking maybe the timing chain has too much slop in it but I haven't checked that yet. I'm just curious if anyone has any thoughts before I start pulling more things apart.

I'd also like to upgrade to a weber carb but I'm hesitant to go that route if I should address timing chain or something else to fix this rpm issue first.

Thanks.

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Unread 03-25-2013, 06:56 PM   #2
BagusJeep
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Are you saying that your headers are gloiwng red after 10 minutes of idle?
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Unread 03-25-2013, 08:00 PM   #3
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Hi SoothSayer and welcome to the forum. I've got an 89 YJ but the engines are essentially the same, as is the carb setup.

Sounds like your O2 sensor is shot (about $18 at NAPA) putting out zero volts which is causing it to run very rich. The MCU monitors the O2 sensor and causes the stepper motor pins to move forward (towards the radiator) in a lean condition (.1v is lean, .9 v is rich) to increase the relative amount of fuel to air mixture, i.e richen the mixture. Replace the O2 sensor first; warm up the engine so that the exhaust manifold is hot and you'll have a much easier time of it.

Next, as you've been into the carb already, the bridge in the carb under the flat plate in the front of the carb which holds the metering rods is adjustable. If you didn't set it properly then it's running very rich. This isn't in conflict with the previous paragraph if the O2 sensor is shot. After replacing the O2, then you'll need to lean it out. The adjusting screw in the center of the bridge is either a #10 Torx or an allen wrench. Counter-clockwise is leaner, clockwise is richer. Counter-clockwise forces the rods deeper into the jets, restricting fuel flow.

Following is some boiler plate stuff which I paste now and then. Virtually everything to need to know is in there. You'll probably have to retune the carb after everything is done but it's not that difficult. Best of luck in your journey

Here are several links which youíll find helpful I suspect. If youíre getting oil in the air cleaner assembly you probably have problems with the PCV system. Get a new PCV valve, about $4 or so and check the hose from the valve to the back of the carb at the base. Make sure itís clear and that the inlet on the carb is clear as well. In the YJís (perhaps late CJ7ís as well) there originally was a solenoid valve in the PCV line physically located between the carb and the head which was designed to block gases from flowing at idle; this was recalled later and removed. If you still have it then run a hose straight from the PCV valve to the carb connection. You can leave the solenoid connected to itís electrical plug and just tuck it away somewhere because itís neutralized, or unplug it and put it in your box of stuff.

Read the topics in the center column of the third link regarding setting the carb idle. The factory settings for the mixture screws is 2.5 turns out from a gently seated bottom. Both screws are set equally, so thatís a good starting point. If you want to tune it then the Best Lean Idle method is a good way to go. Connect a vac gauge to manvac. (If you still have all the emissions equipment, disconnect the larger manifold vac line from the vac reservoir under the battery and plug the gauge in that; this will also neutralize the Pulse Air and Solvac systems while youíre tuning which is a good idea.) With the engine at operating temp and idling, turn both mixture screws in 1/8 turn, bump the throttle a little and wait 15 seconds before doing it again; continue until you reach maximum vac reading and then back each one out 1/8 turn and youíre done.

If you want to verify your tune, put a multi-meter in line between the O2 sensor and itís connection. You should have about .6 volts (+/- .05v) at idle; .1v is lean and .9v is rich.

Hereís the links:

How to read a vacuum gauge:
http://www.secondchancegarage.com/public/186.cfm

How to read spark plugs:
http://www.nightrider.com/biketech/spkplghnbook.htm

Whatís under the hood:
http://home.sprynet.com/~dale02/list.htm

Carter BBD Factory Service Manual:
http://u225.torque.net/cars/SL6/docs/BBD_Manuals.pdf

Carb Trouble Shooting, not BBD specific but useful:
http://www.recarbco.com/technical/newtrouble.html

AMC 258 Torque and HP curves (click on the charts to expand), BBD is lower lines:
http://www.clutchkitcenter.com/media...weber/Jeep.gif


If you wish to rebuild the carb itís easy and the rebuild kit is only about $20, BBD model 8384. Just make sure that you soak it generously with spray carb cleaner (get one with a spray tube on the can to blast it into the channels), let it soak for a 30 minutes or so, blow all of the channels out thoroughly, and then repeat the procedure. Make sure the venturi tubes are clear and that all of the tiny holes in the venturi cluster are clear (use a fine brass or copper wire if necessary.) During reassembly lightly grease (axle grease) the cup that the accelerator pump seats in and make sure that the larger ball bearing goes in the cup. The smaller ball bearing is in the venturi cluster.

As to vacuum readings for manvac, a healthy engine with no vac leaks should be around 22" HG at sea level. Subtract 1" HG for every increase in altitude of 1000 feet. Iím at 9000 and read 15" HG.

I hope this helps.
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Unread 03-25-2013, 10:55 PM   #4
SoothSayer
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Bagusjeep- yes that is what is happening.

Unfocused - awesome response, thanks. that is a ton of great info and I'll start reviewing now. I'll change the 02 sensor out in the next couple of days.
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Unread 03-26-2013, 12:58 AM   #5
thompsoj22
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10 min at 2000 rpm!

Quote:
Originally Posted by SoothSayer View Post
Hey All. New to the forum and jeeps in general. I'm a total newb so bear with me. I have an 82 CJ7 w/ BBD. My jeep with choke plate fully open,fast idle not engaged at all, curb idle screw completely backed out still idles around 2000 rpm. I've pulled the spider web vacuum hose setup and replaced with a K&N filter sitting right on top of carb. Also new hose between dist & carb, carb & EGR, PCV valve & hose new. I pulled carb, scrubbed it clean, rebuild w all new gaskets and cleaned all surfaces. Followed FSM for float, vacuum piston, and accelerator pump adjustments. Have adjusted dist timing as well, not sure the setting though. Installed manual choke as well. Stepper motor is plugged in and pins all the way in.

From what I've read this could be the mixture is way too lean. I've tripled checked for vacuum leaks, solid seating of carb to mani, tb to main body, etc.

Side note i've noticed my borla exhaust headers light up red hot after 10 min or so of idling in garage, this could have been happening for a while and I didn't notice it. I'm guessing this is a result of the high rpms or a clogged cat, or both. I'm thinking maybe the timing chain has too much slop in it but I haven't checked that yet. I'm just curious if anyone has any thoughts before I start pulling more things apart.

I'd also like to upgrade to a weber carb but I'm hesitant to go that route if I should address timing chain or something else to fix this rpm issue first.

Thanks.
thats equal to a ca smog test!. somewhere you are pulling air into the intake system, and your carb will feed that leak from the idle circuit in the carb even though the throttle plate is closed. the glowing headers might be allmost normal at the high rpm that you currently have at "idle". got to verify timing once you get the idle down, mechanical advance is probably coming into play at 2000 rpm?.
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Unread 03-26-2013, 02:00 AM   #6
Matt1981CJ7
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Quote:
Originally Posted by UnFocused View Post
Hi SoothSayer and welcome to the forum. I've got an 89 YJ but the engines are essentially the same, as is the carb setup.

Sounds like your O2 sensor is shot (about $18 at NAPA) putting out zero volts which is causing it to run very rich. The MCU monitors the O2 sensor and causes the stepper motor pins to move forward (towards the radiator) in a lean condition (.1v is lean, .9 v is rich) to increase the relative amount of fuel to air mixture, i.e richen the mixture. Replace the O2 sensor first; warm up the engine so that the exhaust manifold is hot and you'll have a much easier time of it.
Before you start throwing parts at it, there's a simple test to see if the O2 sensor is working, assuming the OP has one

It's spelled out here.

Matt
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Unread 03-26-2013, 05:10 AM   #7
86cj74.2L
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You have a borla header? Or factory exhaust manifold?

If you have a header where is the O2 sensor mounted? If its in the collector 4 feet away from the engine and only has 1 wire on it, its not going to get up to temp. So it will read lean and run stepper in.

With ignition on before you start it is stepper still all the way forward, or is it centered?

Also with idle screw all the way out do you still see a air gap on the throttle plates or are they completely closed?
image-3404795235.jpg  
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Unread 03-26-2013, 10:25 AM   #8
frhrwa
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have you taken a can of carb cleaner and sprayed all around the carb, manifold, etc while the engine is running? just to see if you can find the vacuum leak? sounds like a good leak somewhere and red pipes usually mean extreme lean, but I noticed someone above stated rich? anyway, there's a problem, and you'll find it I'm sure.. (I always used quick start or engine start to find my leaks, but much more dangerous if your fooling around with glowing exhaust pipes..).. anything that will cause the motor to smoke like crazy or stall or rev when you hit that vacuum leak will work..
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Unread 03-26-2013, 11:05 AM   #9
86cj74.2L
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Cherry red headers to me means retarded ignition.
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Unread 03-26-2013, 11:09 AM   #10
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Reminds me of my ex: lean and retarded


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Unread 03-26-2013, 11:35 AM   #11
SoothSayer
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I do have borla headers, w/ air tubes. Original manifold had large hole in it when i bought it last year. The 02 sensor is located just below where the pipes merge into a single pipe. There is no air gap in the throttle plates with the idle screw back out, they are completely closed. Thanks for everyone's help.
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Unread 03-26-2013, 12:59 PM   #12
86cj74.2L
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Quote:
Originally Posted by SoothSayer
I do have borla headers, w/ air tubes. Original manifold had large hole in it when i bought it last year. The 02 sensor is located just below where the pipes merge into a single pipe. There is no air gap in the throttle plates with the idle screw back out, they are completely closed. Thanks for everyone's help.
You should have a 3 wire heated O2 sensor that far away.

Of your throttle plates are closed all the way and have high idle you have a vacuum leak.
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Unread 03-26-2013, 04:56 PM   #13
SoothSayer
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Quote:
Originally Posted by 86cj74.2L View Post
You should have a 3 wire heated O2 sensor that far away.

Of your throttle plates are closed all the way and have high idle you have a vacuum leak.
So should any 3 wire universal fit 02 sensor work for this?
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Unread 03-26-2013, 05:55 PM   #14
Matt1981CJ7
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Quote:
Originally Posted by swatson454 View Post
Reminds me of my ex: lean and retarded


Shawn
I'm sorry, but that was too funny not to repeat.

OP, you gotta find that leak. How have you searched for it?

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Unread 03-26-2013, 06:07 PM   #15
86cj74.2L
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Quote:
Originally Posted by SoothSayer

So should any 3 wire universal fit 02 sensor work for this?
I'm going to say yes. I know my 1988 dodge Daytona had a 3 wire sensor. But you would need the other side of the weather pack connector. A universal you would have to supply your own connector.

Which is easy. Clip your old one off the sensor you have installed now and solder it to the wire that is a different color then the other two. Then the other two wires are the heater. One goes to ground and the other is energized with your ignition circuit.
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