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post #1 of (permalink) Old 05-03-2005, 04:06 PM Thread Starter
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OT Bronco II Stumbles But Passed Emission Test

That about sums it up....1988 B II w/2.9L, one bad cylinder(new plugs 6 mos. ago), coughs plenty when cold, I can still get it to cough when hot, can't seem to get out of it's own way, it idles like crap and it just passed NJ emission test. ?????? The numbers were up there but they weren't close to failing. It uses some oil but doesn't smoke. How can this be?? If an injector was clogged, would it cause that cylinder not to fire and not adversely affect emissions? Well it's legal for another 2 years now but I'm like an old lady pulling out into trafic.....Anybody....any thoughts????
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post #2 of (permalink) Old 05-03-2005, 07:20 PM
 
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Re: OT Bronco II Stumbles But Passed Emission Test

[ QUOTE ]
coughs plenty when cold, I can still get it to cough when hot, can't seem to get out of it's own way, it idles like crap and it just passed NJ emission test. ?????? The numbers were up there but they weren't close to failing.

[/ QUOTE ]

Thats exactly how my YJ runs when tuned for the emmissions testing here. After the test I reajust the carb and plug the EGR vacuum off and it runs great. [img]/ubbthreads/images/graemlins/wall.gif[/img]
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post #3 of (permalink) Old 05-03-2005, 07:34 PM
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Re: OT Bronco II Stumbles But Passed Emission Test

I would guess that a clogged injector would cause a steady miss. If it were restricted but not clogged completely it might cause that behaviour, but would also show up as an overheated sparkplug. Have you pulled them all to see what they look like?
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post #4 of (permalink) Old 05-03-2005, 09:27 PM
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Re: OT Bronco II Stumbles But Passed Emission Test

Aren't Fords SUPPOSED to run like that?

If the injector's totally plugged, or the injector wire's broken you'd have that cylinder without any fuel - just air flowing through it. It could concievably pass emissions tests like that - since it's not technically a misfire - he he - it's a no-fire.

But - sounds to me like ther typical Ford problem, the stumble and no power in one cylinder.
EGR AND the EGR position sensor.
Remove the EGR and Position sensor as an assembly. 2 or 3 nuts at the base of it. Clean the valve portion, it''ll be carboned up, make sure it seals - holds rubbing alcohol in the cavity when turned upside down.

Remove the EGR position sensor on the top of the EGR - 3? screws.

Notice the little stem protruding from the position sensor.

What happens is the spring in the EGR gets weak, causing the stem to get pushed into the sensor too far. That signals the computer where the ERG is - then the computer adds or subtracts fuel and timing. The wrong signal, by even a small amount makes it stumble. Typical Ford stumble -- drive most any Ford and feel it, as time wears on, it gets worse and worse.

Replacing the EGR and the position sensor is what the dealer does - works for about 1000 miles, then it starts in again.

Grind the end off the sensor about 1/16". Not more, not less.
Re-assemble, enjoy.

Another temporary way to verify that will work -- cut a cardboard gasket as a spacer - use two layers of matchbook covers - put it between the EGR and the position sensor - be sure it doesn't touch the pin to inhibit movement.

But clean the EGR first.

The EGR valve hanging open kills one or two cylinders, acts like a vacuum leak, but it isn't. There's no Oxygen in the exhaust being recirculated, making it harder to diagnose.
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post #5 of (permalink) Old 05-04-2005, 05:12 PM Thread Starter
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Re: OT Bronco II Stumbles But Passed Emission Test

A thank you to all. Mr. RRich, I'll do what you suggest. When I changed the plugs there was only one that was really cruded up. I don't think the others were overheated. When I took it to the inspection station I was expecting major problems. When I watched the fellow scrape off the old sticker and put the new one on I just couldn't believe it. [img]/ubbthreads/images/graemlins/confused.gif[/img] Well....Thanks again.
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post #6 of (permalink) Old 05-05-2005, 06:13 AM
 
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Re: OT Bronco II Stumbles But Passed Emission Test

Boy I thought GM EGRs were bad. I think Ford wins again.!!

The EGR in my 4.3 mini van was hanging open randomly making it idle terribly. This is caused by a build up in carbon in the passage that feeds the EGR. THis could be caused by a leaky injector or, in my case, poor valve seals. The carbon breaks off and jams in the opening.

GM revised the program to keep the valve wide open momentarily to allow the particals to fall out. But this is a dealer only fix requiring new proms. They also make a screened gasket to prevent particals from getting in the valve.
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post #7 of (permalink) Old 05-05-2005, 12:39 PM Thread Starter
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Re: OT Bronco II Stumbles But Passed Emission Test

Yep, yep. I changed that booger in my wy wife's Astro van a couple years back. Seems to me the company that manufactured the replacement was Tomco ???. It had a screen I think. It also came with different restrictive washers(different size holes) that you were supposed to look up what engine you had and install the right washer under it. The washers were marked as to their size hole. Soooo I rolled the dice and figured that the less exhaust in the intake system the more power it might have. So I picked a washer that had a hole 2 sizes smaller than what it was supposed to have. By the seat of the pants I thinked it worked, so did the person that drove it every day. And it also passed emossions. Now I know there were a couple variables here and also a couple schools of thought as to how the computer might react to less exhaust in the intake, please excuse me(EXHAUST HAS NO PLACE BEING IN THE INTAKE), thank you, but as someone here said.....there is only so much room in a cylinder and the more ignitable material that is sucked in the more horsepower you get out.
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post #8 of (permalink) Old 05-05-2005, 01:55 PM
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Re: OT Bronco II Stumbles But Passed Emission Test

True --
Research showed that Oxides of Nitrogen NOx forms at about 3000 degrees. Slightly below that temp very little are formed, slightly above that "magic" temp you get alot - 12 different isotopes of it. A normal combustion engine's combustion temperature is slightly more than that - 3100-3200 degrees.

By expermentation, they found that adding a small amount of inert gas into the chamber significantly lowers that temp - below that "magic" temp. First experiments used Helium and Argon. Too expensive, too rare, not enough on the planet. It spaced the molecules apart slightly, lowering the temp slightly -- akin to spacing the BBQ charcoal slightly apart.

Evan Arnold - of LA Trade Tech fame was experimenting with it too. He found that exhaust gas works too. The exhaust has very little oxygen in it - it's all been burned already. The result is a relativly inert gas - essentially a "dead" gas.
By injecting a small amount of that gas into the chambers, it did the same as Helium - and it's free!

In 65? Chrysler failed to meet emissions standards in California, they could not sell one of their engines in Calif! Crisis time.

Evan had already been playing with the solution. He told Chrysler how to fix it - he was their hero! They paid him a bunch and gave him a new Station wagon. I rode in it!
His solution was to drill small holes in the intake's floor into the exhaust crossover, introducing a small amount of exhaust gas into the intake.
They drilled the holes and installed a screw-in orfice - called them Floor Jets. It was a small constant leak, but it worked. They were back in business again!

Find an old Chrysler - open the throttle wide and look down - you can see them right under the carb. They wear bigger, runs terrible like that. Unscrew the jet, put in a pipe plug -- works great!

Later on it was decided it was better to be able to control the amount recycled, so on came the EGR valve. The inert gas is only needed at higher loads, warm. They controlled it with ported vacuum, with a curve similar, yet different, than the spark advance. -- He He -- Another vacuum port on the carb to confuse us! They inhibited it to operate only when warm with a temp valve, sometimes even a transmission switch. More hoses!!!

That caught on.

The famous earlier computerized Fords use a position sensor right on top of the EGR valve - to sense the position of the valve. Those valves were still vacuum operated, but the MCU needs to know if it's open, closed, or how much between.

That input signal has a profound effect on mixture and timing. Unfortunately the way they made it, it's too sensitive. As the EGR spring wears, and the valve seat wears, the EGR opens slightly sooner than expected. That in itself isn't so bad, but the sensor's plunger gets out of position - the plunger moves up slightly too far, causing the MCU to start compensating for the EGR when there isn't any. That = Stumble!

Dealers simply replace both the EGR Valve and the position sensor for lots of $$$ - but it happens again soon.
The "fix" is as I posted. I'd like a nickel for every one I've done.

Newer Fords the EGR is operated directly by the computer - no more vacuum. He He - again they copied GM, but had to get around the patents.

Some engines nowadays leave a small amount of the inert exhaust in the cylinder by modifying the cam's grind for temp lowering. They don't even have ERG Valves. When you replace the cam on those with one that doesn't do that - they really WAKE UP! But may not pass the dyno type testing. The reason dynos are used for testing is to check for Oxides of Nitrogen - NOx - they put it under load.
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post #9 of (permalink) Old 05-06-2005, 03:50 PM Thread Starter
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Re: OT Bronco II Stumbles But Passed Emission Test

I remember the Chrysler fix. Seems to me that when they clogged people were hosed for removing the carb to get at them. When they went 49 state was that the begining of the "Lean Burn" years? What a bunch of hooey. Why the he77 didn't the big three go with F.I. years ago? I think a computer with a carb. is like kissing your sister. Well I guess technology had to catch up to make things smaller, faster and cheeper. [img]/ubbthreads/images/graemlins/grin.gif[/img] Thanks agin....this is good shi*!
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post #10 of (permalink) Old 05-06-2005, 09:01 PM
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Re: OT Bronco II Stumbles But Passed Emission Test

That was a few years ago. Technology wasn't there yet. Transistors were just catching on, computers took up huge rooms, pocket calculators were only in comic books.
We used slide rules back then!!!

Remember the Porsche CD? A good ignition -- but it had tubes!!!

Lean Burn. Something totally misunderstood, and usually mis-adjusted. All it was was timing advance delays. 2 versions, one with dual pickup coils, one without.

The well kept secret was adjusting timing with the screw on the side of the carb - with the brown wire on it - isolated with a piece of cardboard.
Remember it?

Floor jets were kept "secret" for awhile. It was a constant EGR - screwed up idle if too much.

Imagine -- from those years not that long ago to today -- all the advancements. Now envision what it will be like another 40 years from now. Mind boggling!

He He -- Gotta see what the comic books are predicting!

But I'm too old to be able to see it, darn! Even if I did, I wouldn't understand it.
Oh well.

He He -- As we get older, we actually get younger - no hair, no teeth, trouble talking, -- and I think I just wet my pants!
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