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Does my carburetor need a rebuild?

Old 09-28-2015, 09:47 PM
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Does my carburetor need a rebuild?

I have been having a slight misfire at about 1/4 throttle in my '87 carbureted 4x4 pickup. It goes away with more or less throttle. I tuned it up with Denso plugs and wires, a NAPA cap and rotor, and adjusted the valves. It runs a lot smoother now, but still has the misfire. I tried removing the main jet access plug in the carburetor and spraying carb cleaner in the main jet, then leaving some in the float bowl. The problem then got way worse and when I got home my exhaust manifold was glowing red. I am thinking that has to be a lean mixture?

It sat for about a week, now it is back to how it was with just the slight misfire. I tried a different coil, checked for vaccum leaks, etc, and nothing helped. I am thinking the carburetor needs a rebuild, but I wanted to see if anyone here had any other suggestions before I tear into it.

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Old 09-29-2015, 02:28 PM
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I am guessing you have the factory Aisin carburetor? Some of the pivot points can wallow out allowing more air in and really not a way of fixing that. I would look into a Weber. I read on here the other day that a Weber can be made California legal.
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Old 09-29-2015, 08:29 PM
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The main shaft seems to still be tight, although I would be interested to see what kind of power difference the Weber makes.
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Old 09-30-2015, 07:59 AM
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Since you have the stock carb and I assume its a California model there are some things you need to check and eliminate before you dive in. Retarded spark and cam timing will cause high exhaust temps and so will running rich. Running lean will cause high temps in the combustion chamber but running rich won't. Real lean will also cause pinging. The reason the exhaust manifold is red is that fuel continues to burn after it is exhausted. You can ruin your cat this way too!
1st: Check or replace you o2 sensor. Your carb will run rich if its not working. This is probably not the problem but you should eliminate it contributing to any problems.
2nd: Check your spark timing. If its retarded the exhaust will run much hotter. You can actually see the difference in temperature changes by changing the timing and running it at 2000 rpm and observing with a IR gun.
3rd: Check your distributor advance diaphram. It only starts working during cruise, it does nothing at WOT and very little at idle. If its not working then your spark timing will be retarded at cruise. I also have an 87 carb truck and mine has failed and stopped working. I replaced it yesterday so its fresh in my mind.
I'm assuming you haven't done any timing chain work lately? Can we eliminate cam timing?
Once all of this is done look for vacuum leaks and dive into the carb. Since you are having a stumbling issue. Hook up a vacuum gauge into the cab and drive it around. If during cruise its jumping around a lot then its carb or egr related in my opinion. The egr valve during cruise is suppose to open up during high vacuum. Is everything hooked up right?
This may not be your carb although it sound like it probably is.
I don't see any way to make a weber CA legal unless it has an an air valve like the stock carb does. The electronic solenoid controlled valve opens and shuts several time/min to adjust air/fuel mixture. You would certainly have to go through a referee emissions station which can be very time consuming and expensive. Be easier to just get a new carb.
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Old 09-30-2015, 03:43 PM
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I did not think the Weber was California legal https://www.yotatech.com/forums/f114...ssions-291098/ I don't see how it would be but am curious and following this thread to see if it possible. Also I don't really see how you could make an EGR properly function with a Weber. All the Webers mostly remove the EGR from what I see and no way of passing the test without it.

I was surprised to see you had the cherry manifold. I did not think it would/could happen a carb truck. It happens on the EFI more often. I have been fighting the cherry manifold on a fuel injected 22re and is why I am going to carb. I have taken it to Toyota and several other mechanics.
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Old 09-30-2015, 04:23 PM
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Originally Posted by Terrys87 View Post
I did not think the Weber was California legal https://www.yotatech.com/forums/f114...ssions-291098/ I don't see how it would be but am curious and following this thread to see if it possible. Also I don't really see how you could make an EGR properly function with a Weber. All the Webers mostly remove the EGR from what I see and no way of passing the test without it.

I was surprised to see you had the cherry manifold. I did not think it would/could happen a carb truck. It happens on the EFI more often. I have been fighting the cherry manifold on a fuel injected 22re and is why I am going to carb. I have taken it to Toyota and several other mechanics.
I know we are getting off subject here a little. You could make an egr function with a weber. Erg has three inputs, one from the temp vac switch [vsv] and then vacuum lines from the carb. When vacuum is high the erg works, during idle or WOT it doesn't. I think the carb inputs are there.
I read that thread just now. Its on a 81-84. I thought the 87 emissions were complicated! Maybe there is a weber made for CA emissions, but it would have all the same equipment: electric choke, air valve, and fuel cutoff. The o2 sensor would be able to talk to it. CA would require that.
Its too bad in CA. They like to play games with no consideration of the sniff test. I lived there so I know what you are going through. I had a guy from the air resource board tell me that the laws are like that simply to fail cars so people will junk them instead of paying big bucks trying to make them legal.
The last year for a carb 22r in ca is the 1988 model and from what I understand they were right on the edge of failing emissions rolling off the boat.
The trick I used was new spark plugs, changed the oil, fresh gas mixed with some denatured alcohol, and I always passed. Just barely.
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Old 09-30-2015, 06:43 PM
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Thanks for the replies. The timing is correct, and the mechanical and vacuum advances are working fine. The timing chain has about 80k on it, and seems to be ok. I think I can rule out cam timing. I checked the EGR modulator and made sure there were no vacuum leaks in the lines running to it and they were all hooked up correctly. I temporarily plugged the hoses going to the carb from the EBCV, bypassing the mixture control part of the O2 feedback system and it ran exactly the same. I like your idea of driving around with the vacuum gauge in the cab. I will try that in the next few days.

I have driven it on some shorter trips over the last few days, and it has been better than it was the night my manifold was glowing. I have not seen the it glow again, but it still stumbles some. Since I bought my Tacoma a couple of years ago, this truck does not get driven as much, so I have been putting Stabil in the gas. Has anyone had any problems with that? It seems like good stuff from everything I have read.
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Old 09-30-2015, 06:49 PM
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I am probably just going to rebuild the Aisin if it needs a carb, but I have some information that might help with the Weber smog confusion. I believe the Weber is CA smog legal up to a certain year. Probably '83 or '84. Companies can get a CARB sticker to make parts like that smog legal, and I have also heard of an executive order that will make something smog legal. I am in the process of putting a Subaru engine into a Vanagon camper, and the kit I bought is CA smog legal without going to the referee as long as I use everything from their kit and a '90-'94 Subaru engine. I did not know a major exemption like that even existed before that project.

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Old 09-30-2015, 06:50 PM
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I just checked LCEngineering, and they are selling CA smog legal Webers up to '84.
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Old 10-01-2015, 06:17 AM
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Originally Posted by the_supernerd View Post
I just checked LCEngineering, and they are selling CA smog legal Webers up to '84.
This is interesting. I know we are still off subject here as far as your carb goes. I grew up in CA and lived there for 40 years. I learned how to get around some of the rules but I knew someone who helped when I got tested. From what I remember on the equipment side was that any aftermarket equipment: carbs, headers, intakes, had to have all the smog/emissions equipment on them. For example: headers had to have the air injection inlets. Intakes had to have ERG ports etc. So it must be that up to 1984-5 there was no o2 sensor on these trucks, therefore a Weber could be used. Looking at a 1985 FSM, it looks like this was the transition year. Fed standards adopted/changed to much of the CA equipment except an 02 sensor. I could be wrong. I have to go back and look at the emission schematic in that other post.
I know on federal emission 22r's there was not a o2 sensor on carbed engines at all. But there was an airpump before 85 which in my opinion is a pain in the butt compared to an air valve and 3 way cat with o2 sensor. This is the main difference between CA and FED 22r's.
So in conclusion it looks like after 1984-5 a weber cannot be used on your truck in CA. In my area lots of people swap out toyota carbs for webers and they put them up for sale on Craigslist for $40-60. When a car reaches 25 years they are smog exempt in this state. I think it CA there is a cutoff year but I'm not sure what it is. I remember my 65 Mustang was smog exempt but my 70 Chevelle was not. Things may have changed.
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Old 10-01-2015, 10:14 AM
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I went and took a closer look at my '82, and it has both an O2 sensor and an air pump. It is CA smog. It looks like it does not have any kind of feedback system in the carburetor, so maybe the sensor just helps limit oxygen into the exhaust or something. It appears the only mixture control device on the carb is the high altitude compensation system. There are tons of vacuum hoses and switches going to the manifold, so maybe the mixture is somehow altered that way, meaning a Weber would not have to be as complex as a smog legal carb for later years.

'76 and later have to be smogged. It used to a be either a 25 or 30 year (can't quite remember exactly) exemption, but then they capped it some years ago. There are still a few counties, like the one I live in, that only require smog test on the sale of a vehicle.

I am going to just rebuild the Aisin carb on this truck. I could see using a Weber on some future projects, so it is good to know this information!
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Old 10-01-2015, 03:23 PM
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Originally Posted by the_supernerd View Post
I went and took a closer look at my '82, and it has both an O2 sensor and an air pump. It is CA smog. It looks like it does not have any kind of feedback system in the carburetor, so maybe the sensor just helps limit oxygen into the exhaust or something. It appears the only mixture control device on the carb is the high altitude compensation system. There are tons of vacuum hoses and switches going to the manifold, so maybe the mixture is somehow altered that way, meaning a Weber would not have to be as complex as a smog legal carb for later years
Yeah, just looked at an 81 FSM and for CA its set up similar to the 87 which is what I thought we were talking about.
The o2 sensor does give feedback to the carb. When the engine warms up, the o2 sensor will send a voltage to the "computer" [if you can call it that]. The carb runs rich by default which is "dirty" and will cause you to fail emissions when the sensor does not work. When the voltage is low the outer vent control valve on the carb stays closed because its lean, when its rich it opens and lets more air come in through the carb leaning things out. It's activated by one of the wires going to a solenoid on the carb. Its that simple. The valve opens and closes several time a minute.
The air pump pushes air into the exhaust leaning it out. What this does is add more oxygen to the exhaust which helps the cat work. If you are running rich the cat will "cook" itself in short order due to the unburnt gas. The 87 also does this but without the air pump. It uses a one way reed valve which allows air to go into the manifold between exhaust pulses. No air pump, yay!!!
The weber would have to have something like the outer vent control valve I would think. I have no idea how it could be made legal, but apparently it could be. Someone with more knowledge will have to chime in about weber carbs.
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Old 10-01-2015, 07:11 PM
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On the later California 22R feedback carburetors (I had an '87 as well), there is the Electronic Bleed Control Valve (EBCV). It will allow added air into the fuel mixture if the O2 sensor detects a rich mixture. The stock California carburetor has a larger main jet too.

It is located next to the two vacuum switches on the passenger wheel well.
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Old 10-01-2015, 09:20 PM
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Originally Posted by nordicwargod View Post
Yeah, just looked at an 81 FSM and for CA its set up similar to the 87 which is what I thought we were talking about.
The problem is with my '87. I was just commenting about my '82 to help with the Weber discussion. As far as I can tell, my '82 carb just has a solenoid for the evap system going to the charcoal canister, and a fuel cut solenoid. It does not have the EBCV like my '87 has, but my '82 is a ranch truck and could easily be missing a few things. It runs like it is missing a few things .

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