Distributor Vacuum Advance Problem

The advance plate and sleeve need regular lubrication. To do this you remove the rotor and soak the pad below it in the tube with 10W30 oil. You then manually work the plate to get the oil back in it.

The pot there should hold a vacuum when you suck on it.

If the computer sees a bad sensor somewhere, it will put the timing into 'limp home mode' and it will run like a bag of dirt.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

Check for lean fuel mixture, get an air/fuel guage and tune the carb with it.

Check for worn cam and lifters, if you find you can't advance the timing much without knock, and it starts knocking with revs above 2k plug the advance and run it... if you still get knock at higher RPM's; retard the timing until it just idles smoothly (right before the retard causes rough idle) if at that point you still can't totally eliminate the knock when under load or revving higher than 2,000 RPM's then I'd bet on it needing a new Cam and timing set.

I'm betting you had the same knock and ping problems before AND after the carb rebuild and new gaskets right? Which caused you to do the work in the first place. I bet it also starts horribly rough in winter but much better in warmer months.

Air fuel gauge to tune the carb?????

ROTFLMAO! Man there isn't any 'fancy' way to tune that carb. If you need a computer to tell you how to fix them you are screwed and should not go anywhere near them.

For starts, his carb is not 'tunable', he has a computer running it. The idle mix screws are supposed to be blocked with a plug. If it was not put back exactly the same as before, it will run like a bag of dirt.

Now if he has the computer disabled, then it is a different story and he should have stated this.

The computer also runs the timing and controls the advance electronically. There is a mechanical and vacuum advance as well.

If any of the sensors have failed, it dumps the advance down for 'limp home' mode. I suppose he could take a hammer and hit the manifold a couple times to see if the engine stumbles. This would verify the computer is still functioning with the knock sensor at least.

There is about a 15 degree difference in the base timing when the computer is working and not working. With the computer in the loop, you have to use the emissions sticker way to set the timing. I believe that is a set at 1600 rpm with the vacuum line off so the mechanical advance is full, not at idle like you do with no computer.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

Don't be afraid of technology Mike, lean combustion and rich combustion are measurable no matter if there's a carb providing the fuel or FI. Why in the hell do you think his Exhaust manifold has an O2 sensor in it?

Anyone who's rebuilt a Carter BBD and left the POS controlled by the computer (or more accuately the 19 year old poorly working early emissions system) probably deserves the headaches they are sure to suffer.

Just gotta love this new breed of auto 'technicians'. LOL!

If they don't have a computer to tell them what is wrong they are totally screwed.

It is just a 2 bbl carb there Simon, nothing to be afraid of and as I mentioned if you need a computer to tell you what's up, you shouldn't be anywhere near that BBD.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 (More Off Road album links at bottom of the view page)

This from a guy who see nothing wrong with needing to rebuild his carb every year or so. I'm glad you are an expert on the carter BBD you'd need to be to get decent performance out of it, me I have better things to do than devote my life to the minutia of getting a piece of shit carb to work well for short peroids of time between rebuilds, but you knock yourself out.

By the way you forgot to answer to why there's an 02 sensor attached to a carbureted jeep if it can't be used to tune a carb.

Absolutely right, just junk to be tossed aside in favor of better designed, more flexible, more robust, more dependable, more precisely controlled fuel injection.

My fuel filter is any 3/8th or smaller in/out in line filter off of just about any GM or Ford vehicle made after 1986 (ie. throttle body injection to present day MPI). My fuel system was not made by DC.

In my world, kooky make-believe challenges like going through freakin mexico take a back seat to reliability, fuel economy, power, off-chamber functioning, ability to adapt to major changes in altitudes etc.

In other words things that matter and are usefull every day are more important to me than far fetched hypothetical BS

My fuel filter is 10 inches from my TBI

Even if I lived in SD I would consider it BS, as the only way this Jeep is seeing the Baja would be if it were stolen by someone with extremely poor judgment :)

Now stop with the hypothetical BS Bill

"Kevin" wrote in news: snipped-for-privacy@i42g2000cwa.googlegroups.com:

It probably is an air leak, read on...

Yup.

The dash pot/diaphragm advances the spark to maximum under light load when you have maximum vacuum, it retards the spark under heavy load to prevent pinging.

Sounds very much like your dash pot/diaphragm (vacuum advance) is ruptured. Easy to check, just connect tubing to the fitting on the vacuum advance unit and suck. If it's leaking, you'll know it, if it's good it'll hold the advance.

Oh, and prepare for a shock when you go to buy a new one, they're REAL proud of those things for what they are..... :-(

Thanks to everyone who has replied so far.

Mike, I lubricated the distr. advance plate and it seems to have helped somewhat. The pot is holding suction so I think it is fine. I have since been testing every vacuum line and various other elements of the emissions system. I think the Coolant Temperature Switch is bad. I'm getting no change in idle when the switch is unplugged or not. Furthemore, shorting out the terminals of the harness has no affect which tells me a short must exist upstream somewhere. I'm still trying to locate where all the wires go. The switch itself reads .2-.4 ohms whether the engine is hot or cold.

Some other details include it has a brand new EGR Valve which seems to be working correctly and a brand new cat. and purge canister. The Oxygen sensor is fairly new but one of the cracks in the exhaust manifold was just an inch away from the sensor so I don't know if that could have damaged it. If you have more ideas on what to look at first I would love to hear them. Thanks again. Kevin