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Discussion Starter · #1 ·
It is often amazing how much you can learn when you are trying to learn something else. While thinking that I would just check the timing and verify that I had the distributor using ported vacuum I noticed that the idle speed increased when I took the lid off the air cleaner. Then I noticed that occasionally the idle speed would just drop about 300 RPM. 1984 258 I6 original distributor and BBD carburetor.

Well, yes I had the distributor vacuum advance working as desired with the ported vacuum source.

So why would the idle speed increase just by removing the lid of the air cleaner? A dirty air cleaner could do that. More likely is the stream of exhaust gas coming out of one of the Pulse Air tubes. So I have a bad check valve. At this point I do not have vacuum to the "three solenoids", so does this mean I also have a bad vacuum operated control valve on that side too? It is one of those things that you look at and it just seems to display that attitude of "this won't be as easy as it looks". Does anyone have suggestions for making it easier? Should I change the other check valve while I am at it?


So why does the idle speed just drop occasionally? I have a theory that seems promising, but am I overlooking something more obvious? Would the computer be doing this? The best looking clue came from the timing light with the vacuum advance disconnected and plugged, and the two vacuum switches electrical plug disconnected. At the slowest idle speed the timing looks to be 2 ATDC. (Yes I know that 6BTDC would be better.) Blip the throttle open and the timing advances, so mechanical advance is working. The idle speed stays a bit high, timing is around 8 BTDC. After a little bit the idle speed drops to slow and the timing is now back to 2ATDC. So my theory is that the mechanical advance is sticking and takes some time to get un-stuck when RPM drops to idle.
I haven't been this deep into a distributor for a long time, so can I get to the mechanical advance without removing the distributor from the engine? Any tips on fixing this?
Detail: the decal says 16BTDC @ 1600 RPM
 

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You can get to the mechanical advance by removing the hold-down screws on the breaker plate. But to check how it's working just twist the rotor and let the springs bring it back. If there are catches in the motion or it doesn't go all the way back you probably need to clean and lubricate the springs, weights and pins. It's not difficult at all while still on the engine.
 

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Discussion Starter · #4 ·
Status update 1

So off I go to NAPA for a new check valve. The guy doesn't have a clue what a Pulse Air Check Valve is, gets help looking through an old book. They finally pick one (called an Exhaust Air Valve) that is listed for my year of Jeep. Yeay, it's in stock (that should have made me suspicious!). Several days later I finally get up close to do the replacement work. Ooops, I don't have wrenches that big. Uh-oh, the new one doesn't look like the old one.

1. I need 1-1/16 and 1-1/4 wrenches, over $40 from Sears or a few dollars less at NAPA. More shopping needed. Finally decided on using my BIG adjustable and purchased a smaller adjustable (goes to 1-1/8) at Home Depot for $14.

2. Back to NAPA to better describe what I need. They don't have it in stock. I decide to wait until I can bring the old one in for them to look at.

3. I'm now suffering withdrawal symptoms from my addiction to Jeepin' on Mountain Trails. Any suggestions for capping this tube so I can get back to the other issues without having exhaust blowing into the engine compartment. The old valve is still there, the hose end is 7/8 inch. I don't want to plug the rubber hose as I don't want to expose it to any more exhaust. The tube end of the valve has threads on the outside. The metal tube has a nut around it, so I assume there will be some kind of flare on the end of the tube.
 

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Careful use of pipe wrenches should work - be careful not to bend or ruin the thin fragile tubes - they are getting scarce and expensive. Soak them with PB Blaster first for as long as you can.
When replacing the valve, liberally use graphite anti-seize.

You should be able to drive it fine with the hose disconnected from the air cleaner, just flopping - leave it open, tie it somewhere the heat coming out won't burn anything. It'll be a bit noisy though. Be sure to tape off the air cleaner tube - it's a direct inlet for dirt bypassing the filter.

You may find the hose next to the check valve being charred and brittle from the heat leaking past the valve.
 

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Discussion Starter · #6 · (Edited)
Distributor efforts

I think I'll split the thread into Distributor and Pulse Air Check Valve.

So why does the idle speed just drop occasionally? I have a theory that seems promising, but am I overlooking something more obvious? Would the computer be doing this? The best looking clue came from the timing light with the vacuum advance disconnected and plugged, and the two vacuum switches electrical plug disconnected. At the slowest idle speed the timing looks to be 2 ATDC. (Yes I know that 6BTDC would be better.) Blip the throttle open and the timing advances, so mechanical advance is working. The idle speed stays a bit high, timing is around 8 BTDC. After a little bit the idle speed drops to slow and the timing is now back to 2ATDC. So my theory is that the mechanical advance is sticking and takes some time to get un-stuck when RPM drops to idle.
I haven't been this deep into a distributor for a long time, so can I get to the mechanical advance without removing the distributor from the engine? Any tips on fixing this?
Detail: the decal says 16BTDC @ 1600 RPM
So I get into the distributor and this is what I see.

For an even larger view click here
I can't find a problem with the movement of the parts. The weights swing freely, the rotor advances smoothly and always returns all the way against the stop. Yes the larger spring is loose from the round post, but that just allows the smaller spring to do some quick initial advancing.
My Haynes book shows that there should be a wick piece inside the top of the shaft (below and inside of the rotor). There wasn't one. My guess is that it would occasionally supply a little oil to lubricate the inner and outer shafts.

All that I can see to do here is clean the corrosion off the springs and look for some light grease to lubricate the weights.
 

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Discussion Starter · #7 ·
Check Valve status update 2

I think I'll split the thread into Pulse Air Check Valve and Distributor.

So why would the idle speed increase just by removing the lid of the air cleaner? A dirty air cleaner could do that. More likely is the stream of exhaust gas coming out of one of the Pulse Air tubes. So I have a bad check valve. At this point I do not have vacuum to the "three solenoids", so does this mean I also have a bad vacuum operated control valve on that side too? It is one of those things that you look at and it just seems to display that attitude of "this won't be as easy as it looks". Does anyone have suggestions for making it easier? Should I change the other check valve while I am at it?

For an even larger view click here
I found out, without damaging anything, that the big nut on the end of the tube doesn't unscrew because it is welded to the tube. The Valve simply un-screws from that nut. I had to get the two wrenches in place so that I just needed to squeeze the handles together, but then I couldn't get enough leverage. So I added some big pliers to squeeze the wrenches and it came loose easily.

So now it is out and after a couple of hours visiting all the parts houses in town (NAPA, Car Quest, Checker, Advance, AutoZone) only two of them knew enough to figure out that what they had in stock wasn't what I need. NAPA had one that should have been correct, and Car Quest said they have one with the correct thread size but smaller hose end. Monday I'll be off to visit the dealer, and maybe on to the used Jeep yard. So now I am wondering if a PO might have changed to a non-stock setup. Can someone tell me if this photo looks like what they have? It has a 7/8 inch hose end.

It has NOK and a couple of numbers on it, but no one could find a cross reference to the numbers: 6H2S EF893300478.
 

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if these are what you're looking for, i have them.





i bought them for my 87 yj but never used them or removed from the box. if you would like another pic of them out of the box, send me a pm.
 

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Discussion Starter · #9 ·
Distributor update 2

I never could find any binding of the mechanical advance pieces. I brushed up the advance springs to make sure that there wasn't some corrosion keeping them from fully contracting. I lubricated the sides of the weights. I didn't lubricate the pivot point of the weights because I didn't want to risk breaking those old plastic retainers. I put a couple drops of oil to lubricate the inner & outer shafts. Put it all back together and it runs, but not well.

Does this sound familiar to anyone?
From about 1000 rpm and up it runs the best, and will idle at 1000 rpm, and responds quickly to any throttle change. Whenever it drops below 1000 rpm it quickly changes to a rough idle that is around 600, with the speed jumping around by +- 150 rpm, and responds slowly and poorly to any throttle change.
With it idling at 1000 rpm I can engage the clutch a little to drop the rpm and every time it will go to the rough idle. If I give it any amount of throttle to get back up to 1000 rpm then it will stay at 1000 rpm.

Any suggestions for what to look at next? I have to get this fixed or else grow a third foot to be able to operate all three pedals while on the trails.
 

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Discussion Starter · #10 ·
I have investigated the wiring for the distributor, and have verified that this Jeep does not have the Nutter Bypass. So the computer is in the game.

I am learning and renewing old memories, but I don't think I'm winning in this game yet.

I will go see if Radio Shack still carries that spray TV Tuner Cleaner and clean up all the ignition connectors. What kind of cleaner would you guys recommend for electrical connectors that doesn't leave a residue?
 

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Discussion Starter · #11 ·
Distributor update 3

It is running better now, which seems to be a combination of multiple things. You can read about the other things in the thread for connecting dangling wires.

I think that getting the BBD carburetor working better allowed dropping the idle speed below 800, and a much steadier speed. It appears that the smaller spring in the distributor mechanical advance starts to advance by 1000 rpm, so that had been throwing the timing adjustments off. Now with a normal idle speed I could set the timing at 6 BTDC. Ohhhh so much better.

Thanks for the explanations and advice.

The reward for these improvements is getting back on the trail and having it run better than for at least the last couple of years. :)
Yes, the CJ7 is in the picture.
 

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