Cartoonweirdo

I drive a 1980 p/u with california emmisions and have an idle issue (surprised anyone?).

The problem: When cold the truck misses and idles low (around 1000RPM), after heating up to about half way to normal operating temperature it hits high idle, after warming up all the way it runs fine.

A bit of background. I have had the clutch and transmission replaced, and when the head gasket blew had the engine rebuilt, and replaced most of the under hood items (water pump, thermostat, radiator, vacuum hoses, had the carb rebuilt).

Imediately after leaving the engine rebuild guy's place (three or four months ago) the electrical system failed. I finally diagnosed and fixed that. Ran well enough for a while, then poorly, I pulled the air cleaner out and it was full of oil and soot. Traced it to an exhaust leak at the manifold feeding exhaust back into the air cleaner when the truck was cold (HAI system), disconnected that and currently running with the exhaust leak. Called the rebuild guy back, he's sold off his business and left town. New guy won't honor his warantee, and I'm not too sure if I want to have the old guy fix it anyway if his work is this awesome already.

In an effort to see what is going on I have done the following: Clean the oil out of the carb (carb medic), Replace the basics (air, oil and fuel filters; cap, rotor, wires, plugs (fouled with oil), oil).

Checked the choke, and choke breaker (work), checked the timing (fine), checked the vacuum advance (front diaghphram advances the timing. Back doesn't, but then I'm not at high altitude), checked the AAP (no gas in the vacuum line, when I pull the vacuum line it squirts gas into the carb when cold and also when hot. This would explain a slight lag in HOT acceleration but should be fine when cold right?)

Other clues:

The air pump (the one for the pollution controls) may not be working. I can't feel it sucking any air out of the air cleaner housing.

The choke and the high idle seem to be acting independantly. As the engine warms up the choke opens. Around the time it is fully open (even without the hot air off the exhaust manifold) the high idle STARTS. When the engine comes up to normal operating temperature a blip in the throttle drops it back to warm idle.

Every so often the throttle will stick wide open. Blipping the gas pedal drops it back to normal. My assumption has been throttle linkage.

There is a periodic miss at all times. It is small but noticeable and occurs every five or six seconds. This is different than the miss when cold which is constant and causes extra smoke in the exhaust.

I live in Portland Oregon, and have to DEQ this thing or I would have removed the vacuum tube forest and gone to a simple carb long ago.

Thanks for all your help,
Carl

greaseyknight

I would give the truck a compression check just to make sure that that everything is good in the motor.

Then check to see if the throttle shafts and butterflys are not worn out, as I've been told that excessive wear can cause idle problems.

It sounds like the vacuum hoses are all mixed up, the fast idle cam should get no vacuum when the truck is cold. Test the BVSV (its should have 4 ports and is in the intake manifold) and see which port is closed when cold and connect fast idle to that. The AAP should get whatever port is open when cold and closed when hot.

Your best bet would be to find the vacuum diagrams for your truck and go through everything and make sure that its hooked up correctly.

Hope that helps, the best long term solution may be to install a weber, redline claims that the kits that they sell are emissions legal, but I have no idea as we don't have to smog in my part of WA

Cartoonweirdo

Hi Greasey Knight,

Those are very good points, and I have been casting around for a compression gauge since around 9 this morning. If no one has on by the weekend I will have to buy one.

I have a diagram and will check the vacuum hoses. If there is source for actual vacuum switches and etc I have yet to find it (other than u-pull-it) and it occurs to me that if one of my many VSV's or TVST's is giving up the ghost after 30 years that I might have to investigate Redline's emissions legal claims. In practice I have always seen a small variance between the actual truck and the diagram (perhaps that has always been the trouble eh?)

My question is what to look for on the butterfly and throttle shaft. Never rebuilt one myself (some else did this for me the last time and I'm half convinced that that might be the trouble) so not sure. Can I measure the size of something with a calliper or ruler? Are there photos? At this point I am so sick of less than capable mechanics billing for sup par service that I have vowed to learn the mechanics of the thing myself (albeit the hard way).

I'll let you know what I find out after a few days of blueing up the air around my front yard with a combination or swear words, exhaust fumes, and beer vapors.

Many thanks,
Carl

greaseyknight

As for finding a BVSV, good luck, when I broke mine I had to get another from a junk yard. I don't think that they are made any more, however I saw that someone had installed one from something else. A good parts guy might be able to find you one that works.

As for the throttle shaft, I have no idea what the specs would be as to what is worn out. I would check the shaft the connects to the throttle cable and see how much back and forth play there is. I checked the one on my truck which works great, and there was a little bit of side to side play.

How many miles are on this truck? This would give us a good idea as to how worn the carb is. And have you checked for vacuum leaks yet? The best method that I heard was to use a unlit propane torch that has the gas turned on. You start the engine, and hold the torch by the vacuum hoses and the base of the carb to see if there are any leaks, if there is a leak the engine will sound different.

Cartoonweirdo

No idea how many miles as the odometer has only five digits. I suppose that could be two, three, or perhaps four hundred and 70 something thousand but I can only read 70 something thousand.

As to vacuum leaks I preformed a similar test with spray starter fluid and found no leaks (doesn't mean there aren't any, but that was my first guess).

I've located a compression tester and will cease speculation until friday or saturday when I see if the carb and pollution controls are even worth messing with (no use if the bottom of the engine fails the test).

One last thought. Could it be that the overall mixture is really rich? I can smell a small amount of gas as a regular thing but had previously chalked it up to the exhaust leak.

Thanks for all your input.

Carl

Al's Chop Shop

what are your DEQ readings?

Al

Cartoonweirdo

No clue,
I'll run her through early next week and let you know.

Carl

hilux80

i had a similar issue with mine a few days ago. the high idle kept getting stuck and it would sometimes idle up to about 3500rpm. having just rebuilt the carb it kinnda stunned me......i traced everything today and found that the secondary butterfly was at fault it was just gummed up to high hell. a few shots of carb cleaner later my problem was solved. hope this could be of somrkind of help to you

Cartoonweirdo

Finally got back to it:

Compression test is fine (170,170,175,170);

Plugs are slightly fouled with oil (how long after a rebuild should this condition be allowed to persist before suspecting seals?).

An exhaust manifold stud had come out of the block and was the culprit in causing the leak. I replaced it and the problem is better, but not gone. I am on the way out to the truck to set my idle screws in hope that a too rich mixture is the culprit.

Anyone with ideas?

Anyone with experience putting an after market carb on a cali emissions truck in an area that requires emissions testing?

beck85

Dont know if it applies, on my 85, 22R I disconnected the temperature switch. And it stopped all that nonsense at idle. I still dont know just what the freakin switch is good for....or how it functions in the scheme of things.

thebrick

Check your vacuum hoses and get your exhaust leak fixed. A helicoil kit from the parts store is cheap and easy to use, just make sure you have a good manifold or get a smog legal header. I just slapped a thorley header on mine.

I have the repair manual for my 80 20r. if you need help with the vacuum lines i have the diagram.

thebrick

Also, i am doing the carb thing too.

you can get a weber 32/36, but some people dont like them. they are smog legal ( https://www.yotatech.com/forums/f120...stions-207253/ ).

i am going to be rebuilding the carb from a 22r and putting that on. I got an adapter plate from LC Engineering for 30 bucks and a K&N filter kit/adapter for the 22r carb for 12o(?). you might get lucky and find a cheap 22r carb and get a rebuild kit from napa auto parts for like 40 bucks. still brings you in under the price of the weber.

The weber is 325cfm progressive 2bbl. the aisin 22r carb is 326 cfm progressive 2bbl. so the only difference is the weber gets rid of most of the vacuum tubing and is tunable with jets and stuff. some people don't like them, some do. I choose to go with the 22r carb because of cost and my parts guy had bad experiences with the weber. (said they need a rebuild every 3 or 4 years. Hope it helped. I had a similar carb question in the 1st gen truck forum, if you wanna search for it.

The only question i have now is what to do with my PCV system since the old one fed back into the airbox, but the K&N box doesn't have that option (I think).

EDIT: i dont know if the weber is legal in oregon, but since CA allows it i bet oregon would.

ducatipaso

I know this is a year old thread, but I live in Portland and am about to do this same swap. I'm eyeballing the redline 32/36 kit as I've used webers in the past on other applications.

Regarding Oregon requirements, I had a chat with the fellow at the DEQ station last time I was there. He said that my '79 requires no visual inspection other than for the presence of a cat. He said it will be subject to a tailpipe test and has to pass the requirements for a 1979 truck, which are pretty lenient.

Bottom line... you can do whatever you want under the hood here in OR on an older truck like this. I was under the impression that anything pre OBD2 was subject to the same rules as above.

I'm looking forward to doing this swap.

imspidey

I too am in Portland trying to pass DEQ....unfortunately someone yanked the cat and definitely running too rich on fuel...hcs were a whopping 4300! legal is 220....best suggestions to get the fuel burning more efficient before I put a new cat on??

ducatipaso

have someone with an EGA set your carb, then replace the cat. you'll blaze through DEQ.