CJ7 barely failed emissions

So far so good....

The O2 does go rich lean, rich lean. The computer has dick to do with it, it does that when unplugged even. It is the O2 sensor that makes the computer 'dance'. Or the stepper pins dance...

This is a compromise to get a good 'average' sampling rate fast enough to have a stable tailpipe emissions. The stepper motor is a mechanical device after all and can only physically move so fast. There is a D/A converter involved here.

When we do it manually, we don't need to compromise like the computer does because of the limited number of 'steps' on the stepper motor, we can set it exact and pass emissions quite fine.

That above scenario is what I am saying and I stick with the thought that the sampling rate and A/D and D/A converters in the computer with a mechanical stepper motor on the mix will do exactly as I see it doing, one 'slightly' rich carb due to a partially blocked tube or something as I described.

Below you are talking about manually trying to make up for a carb defect which is not applicable to the above scenario with a perfectly stock carb.

All bets are off when the factory set of the mix screws has been moved. Then we are no longer talking 'stock'. Then you either guess and get tested to see or you have a sniffer up the pipe while 'guessing' to get it back to factory range on the stepper or fix the carb or kill the computer and just manually set the mix.

Mike

fail by much,

Wrong. The O2 sensor is a tool that the computer uses to monitor mixture changes. The stepper motor is the tool the computer uses to change mixture. The computer changes mixture via the stepper motor and looks at O2 sensor input to see the results. The O2 sensor isn't a smart device. It's the computer that runs the show.

Your thinking is just like most untrained people think, but it's wrong.

Whether there is a D/A converter involved or not isn't relevant when you're discussing who's running the show.

On new fuel injected vehicles, you still see the O2 sensor switching from rich to lean, and there is no mechanical device involved in changing mixture. It's done by changing the length of time the injector is open. The computer changes the mixture that way because that's what it has been programmed to do.

If you could set it exact, there would be no need for a computer. The manual setup is the compromise. It doesn't change with conditions, and you don't get the correct lean/rich switching needed for tighter emission control.

And you're still wrong.

If the factory setup was perfect, and should never be moved, why do you think they would put adjustable mixture screws in? The idea of sealing the mixture screws was to keep somebody who didn't know what they were doing from screwing it up. If they were never meant to be moved, it would have been a lot better if they weren't adjustable, don't ya think? They knew that in the real world, adjustments would be necessary. There is no guessing about getting the adjustment where it belongs. In fact, it's a simple procedure, and you don't use a sniffer to do it.

Don't feel bad. A lot of folks don't get it.

(lean or rich)

fail by much,

weather). So here

much higher by

Well sir, I give up.

You just want to talk in circles and still haven't addressed my original scenario which I say is 100% correct.

All you want to do is cut open a stock carb to mess with it once it is broke.

That was not in my original premise on how a mechanically operated although computer controlled carb can be slightly rich with a slightly blocked idle tube.

I have a real one track mind here guy, and tossing bllsht at me ain't about to change it.

Now if you knew what the computer sampling rate of all the sensors it needs to read before changing anything was and the A/D input lag as well as the D/A output lag and maybe what the maximum speed of a stepper motor change was then maybe you could convince me that the computer can compensate for a mix that 'needs' to be at 3.25 turns or 'steps' out because of a blocked tube instead of the even 2.5 turns or an even 2-3 step pulse it was factory set at.

Mike

bllsht wrote:

sealed mixture

(lean or rich)

didn't fail by much,

testing on a

weather). So here

much higher by

months. Would an

LOL!

You have no clue how the computer does it's 'thing' and just 'why' the factory setting has to have the mix match the D/A timing pulse of the stepper pins do you?

Mike

bllsht wrote:

to correct.

is moving in

it running.

sealed mixture

probably too

they're doing.

mixture (lean or rich)

didn't fail by much,

for testing on a

weather). So here

are much higher by

months. Would an

other hints? I

So tell me. When you adjusted your idle mixture, how did you match the mix to the D/A timing pulses?

Oh, you didn't?

Why not?

Don't they give you that info in the service manual?

Why not?

Why is it important for the factory settings to match this, but not adjustments made in the field?

If they should never be moved, why are they adjustable anyway?

Why does the factory service manual give you the procedure to remove the plugs, and adjust the mixture, but mentions nothing about D/A timing pulses?

There's also adjustments for the main metering circuit, and they don't mention D/A pulse timing either. Doesn't it need to match at higher rpm also?

Why is that stuff adjustable?

This should be good.

You're just throw>LOL!

too rich, or

to correct.

correct the

is moving in

it running.

sealed mixture

probably too

they're doing.

mixture (lean or rich)

didn't fail by much,

for testing on a

weather). So here

are much higher by

months. Would an

other hints? I

Actually, that's not true. For documentation, please refer to the Jeep TSB I am posting separately under the subject: "BBD Carburetor - Idle Mixture Adjustment TSB"

Well, still true.

You still have to cut the carb open to set it. A 'stock' carb has the mix screws blocked from the factory.

Mike

I guess you've noticed by now that facts mean nothing to Mike.

That's like saying that once you adjust your brakes, they are no longer 'stock'.

Give it up.

I have no problems with read NOTE: THE IDLE MIXTURE SHOULD ONLY BE PERFORMED IF THE ADJUSTMENT SCREWS WERE REMOVED DURING CARBURETOR OVERHAUL FOR CLEANING PURPOSES

Or as it politely doesn't say: If you screwed up and forgot to count the turns upon disassembly like the other manuals state.

Pay attention now, I'll type it slow even....

It does not say to do this as part of a 'normal' tune up.

It does not say to cut up or leave cut up your carb up so you can do 'field' adjustments.

In fact it pointedly states, Quote:

"10. Install RTV in the idle mixture screw plug holes."

That would effectively turn the carb back into it's 'stock' form with only the idle speeds and choke rich available as 'field' or 'driveway' or 'tune up' adjustments.

If it goes out of emissions spec, it needs to be cleaned, not cut up and dicked with to try and compensate for a blocked tube or passage.

Simple eh?

There, now I hope that wasn't too difficult to understand was it?

Mike

Man, you 'really' need to actually 'read' what I write, not just guess at it's meaning....

The above was taken out of context and you know it.

For Sure there is a factory stock adjustment on a freaking carb, manual or computer controlled! I stated that wayyyy back in this thread.

'Stock' means plugged idle mix tubes as that TSB also indicates.

Mike

Hmmm, I have the below message in my sent box and someone quoted it on the newsgroup, but I can't see it or find it there on my server so I am going to repost it.

It was sent Sunday, Aug 10th at 12:13 PM.

Mike

---------------------------------------------------------

See, here you go again with all this 'adjustment' BS.

There is 'NO' idle mix adjustment on a stock Carter BBD with a stepper motor!

You seem to have a mental block on this simple fact and keep insisting you have to cut up or drill out a carb to get it running right, rather than cleaning and putting a kit in it to properly fix the problem.

'My' carb has nothing to do with the scenario I outlined, mine is 'not' stock and I do not have a computer moving the stepper motor.

I will fill >

to> the D/A timing pulses? >> Oh, you didn't? > Why not?

No functioning computer on mine.

It is a 'factory' set that is 'supposed' to be set exactly back as it was before it was disassembled for cleaning.

The carb kit also comes with replacement 1/4" x 1/4" plugs that are to be pressed back in after a clean.

adjustments made in the field?

There are no 'field' adjustments available on a 'stock' BBD with stepper motor besides the idle speed and choke richness.

For a base or factory setting to have the stepper pins dancing evenly between step 2 and step 3. In other words to have it 'exactly' in the middle of that 2-3 step pulse so the rich/lean pulses are timed even giving a stable emissions mix. (see my original scenario)

Carter just uses the exact same base plate for the regular manual BBD and the electric BBD. They just block the electric BBD's mix screws with solid plugs, unlike the tin cap they use on the manual BBD's screws that can be popped out with a screwdriver for 'field' adjustments.

plugs, and adjust the mixture, but mentions nothing about D/A timing pulses?

There are two different Carter BBD's, the book has adjustments for the manual carb mix but for the electric one, it just says, Quote: 'Idle adjusting needles (part # 54)- turn in until lightly seated, then back out the number of turns counted on disassembly'. End Quote.

Pretty simple eh?

If the carb has a fresh kit in it and everything is clean, the factory setting is the only correct one.

To get a messed up one back to factory would require a sniffer in the tail pipe while you are adjusting it.

Yup, it does.

And if the factory set on the mix screws is still there, then the 'book' adjustment on the vacuum piston assembly is correct.

Start messing with the mix screws, and then you need to start messing with the vacuum piston adjustment to get the right high speed mix to pass emissions. Been there, done that, on a 'manually' set up carb only.

No two carbs or engines are made or adjusted 'exactly' the same. The factory has to be able to fine tune everything.

And some parts like the base plate are just used on different models to save design costs. They just modify them slightly like with the solid plugs on the mix screws instead of the pop off/out caps.

Like they put the sol-vac unit on all the carbs, but only the automatic or AC equipped vehicles have the set screw in it so it actually functions.

The 'only' reason to ever take out the plugs on the mix screws on the base plate for the electric BBD is to disassemble them for proper cleaning.

I hope so. Maybe I explained it well enough for you to catch on...

Mike

equipment on

scope, but

make the O2

mix to achieve

the stepper

too rich, or

try to correct.

to correct the

motor is moving in

keep it running.

have sealed mixture

It's probably too

they're doing.

The computer

mixture (lean or rich)

You didn't fail by much,

in for testing on a

wet weather). So here

are much higher by

couple months. Would an

other hints? I

Not the case, really. Mike's a good guy. He's been a lot of help to a lot of people. He's just not always right. No big deal.

Yup, I agree.

Mike