Removal of emissions control on standard carburettor

[jameshewitt95]

Hi everyone, I am attempting to resurrect my manual '86, and I am having a problem with the engine where it starts to die slightly as you take off, but when there is some momentum, the engine picks back up again and drives normally.

I assume this is some kind of vacuum leak in all the carburettor emissions control lines. Before I go and replace them all, I thought I would see if anyone has removed them.

Is there a simple way of removing all of this while just keeping the standard pressure actuator for the choke? I don't have to pass emissions standards, so no legal problems for this in case someone wonders.

The car idles well, and appears to drive reasonably well once moving. Just the clutch out transition when the engine almost does. I also know the carburettor needs a good tune, so removing all the emissions stuff might make that easier.

[Mark]

When you accelerate suddenly with a carb, there is a slight period when the airflow increases faster than the fuel can catch up so it is temporarily very lean and lacks power. The acceleration pump is supposed to fix this condition. I'd take off the air filter cover and look down into the carb when quickly pushing on the gas pedal or throttle linkage. You should see a quick spray of fuel going into the carb. If you don't, this could be your problem. There is also the auxiliary acceleration pump which gives another extra spray of fuel when the engine is cold. The diaphragm in this one is almost always damaged so it doesn't work. If you accelerate more slowly, does this delay still happen?

[Petros]

I would advise against just ripping all the vacuum operated systems out of the car, it is very difficult to get it to run properly. the fuel and induction system was designed to work with those systems in place. And many of those systems improve drivablity and fuel economy, there is not reason to remove them, but you do need to fix them if they do not work. that is not difficult, it takes more time to track down the problem than it does to fix it. but if you just pull it off off you will end up with something that many not be drivable. each system is not that complicated, study the service manual to understand what they do, and determine if you want to really remove them. take them one at a time and it is not that difficult to understand what they do, and why they are there. Doing this will also help you find the problem.

It is not that difficult to systematically go through each system and test them, there is a procedure in the Factory service manual, once you know what to do it only takes about 20-30 min to test all of the systems. the tests are simple and do not usually require any test equipment or special tools. but the first thing to do is to compare your vacuum diagram with your engine, and trace each vac line from end to end, inspecting for leaks and that it is routed properly. usually that is the cause of the problem, misrouted or disconnected or leaky vac lines. once each vac line is verified to be good and installed properly than you run the tests on each system per the FSM procedure.

that being said, there are a few systems you can by pass or remove that will not affect the drivablity. the EGR can be removed and the ports capped or plugged, the warm air risers can be rigged to only take cold air, it will run fine without it unless you live in a place that has subfreezing weather (it keeps the intake air warm to prevent ice formation in the carb), and if the auxiliary acceleration pump (AAP) diaphragm is leaky you can cap off both ends without serious consequences (it only operates when stone cold during hard acceleration to prevent a flat spot when cold, once warm it does nothing, if leaky it will eat gas and make it run like crap).

Most of the others can be by passed, but you need to study in the FSM what it does and how to by pass it so it runs properly. often you will lose an important feature, like the High Altitude Compensatory (HAC) can be removed, but when driving over 7000 ft or so, the car will run too rich, this feature leans the mixture and advances the spark slightly to compensate for the thin air. If you never drive in high mountains you will not miss it, and even when you do, it will still run, it will just run rich.

[jameshewitt95]

Thanks for the advice guys, I live in Australia, so no cold and no serious elevation to worry about. I will definitely be deleting the EGR. But this isn't a long term thing, the engine will be replaced in the not too distant future for something interesting once my Land Rover project is done. I just want this to cart engine parts, etc around as my Commodore sedan isn't good at that...

I have been investigating the AAP, and there does appear to be a jet of fuel when manually pushing the pump. Would a split rubber boot cause issues? I didn't see any serious consequences of it except for turning any lubricant into cutting paste, of course. (Photo attached)

The larger vacuum hose going up to the air box is split (attaches to the small white plug in the box, no idea what it is) but it seems to be part of the warm air business, so I take it that isn't all that useful if I live in a hot climate?

[Petros]

Do you mean a split in the accordion boot on the plunger for the acceleration pump? that will not harm a thing if it is cracked, it is just a dust boot. the actual seal on the piston is down inside the carburator along slide the float bowl.

you can put some sealant or RTV on it to keep dust out if you live in a dusty area.

many of these boots on my Tercels were cracked, or partly or fully disintegrated, and it does not affect the way it runs at all.