Carb Choke Plate to Provide TBFI Properties

[Joseph812]

Hello all, I have an '87 Nova with carburetion problems like stalling and apparent lean mixture. I'm thinking about controlling the choke movement to adjust the fuel/air mixture as needed. The object would be to obtain some of the properties of TBFI, throttle body fuel injection. However, fewer control parameters ought to be necessary to address since the carburetor works well enough on its own and just really needs quite a bit of help.

I'm hoping to get acceptable running as easily and inexpensively as possible, and adding external control of the choke plate would enable me to try to address apparent bad accelerator pump function without messing with the internals of the carburetor. I drive so few miles per year that I will be satisfied just to get improved running that can permissibly fall somewhat short of the original quality. I'd like something more automatic than a manual choke, though. Thanks in advance for your ideas.

[shadows]

get your vehicle to a good mechanic
you have a basic carb, you still have a computer
you try to control manually the air going in- you have major issues
most likely- your engine is in poor state of tune
your carburator has been tinkered with

properly working carb on your vehicle which is in a good state of tune you would have a hard time improving on factory settings

[Joseph812]

"your carburator has been tinkered with"

Alas, when it failed the emissions test several years ago, it was worked on and after that I remember it not running good anymore, except for good idling when the engine is warm. I'm indecisive because the car could maybe best be categorized as beyond econonical repair.

I heard that it has a computer and you have confirmed that.

"properly working carb on your vehicle which is in a good state of tune you would have a hard time improving on factory settings"

I agree with that, and I have considered replacing or rebuilding the carb.

[shadows]

in case you aren't sure about the engine-
do a compression check of all cylinders
hook up a vacuum gauge when it's idling warm

carburators in those days were finiky- takes a good carburator man to take one apart, clean, replace what's necessary- depending on who and what was done- it might be wise to pick up another carb- exactly the same- and take it to a carb man

question- long ago- was it sitting, not driven, and then you thought you had carb problems- maybe haven't drivin it much since- is that what you're saying

[Joseph812]

The car has about 200k miles on it so it might have lost some compression. Golly, I remember having one of those vacuum gauges that I used years ago, and that is a cool way to get a general idea of engine compression that I would have been unlikely to think about myself these days. One good sign about the tightness of the piston ring seals is that the oil doesn't seem to get dirty fast after an oil change like on other old cars that I have had.

I should admit that I'm rather house-bound these years and that is why the option of adding on that choke gadget looked possible to me. It could be done (if it could be done) basically without much altering the present state of the car. And that is a reason why having a spare carb like that and rebuilding it before trying to put it on appealed to me some.

Answer to that question- indeed, the chicken or egg or probably even both are involved in the scenario. I got the car back, it ran worse, but that was probably already after spending the required $300 dollars on emission repairs (family took care of it for me). So I got annoyed driving it and took that as impetus to bicycle to get my food. So the car began to sit more, and that messed up the carb even more.

Indeed too, bicycles attract me because they are simple, generally easy to cope with and small, unthreatening, and manageable; lightweight, low maintenance, and easy to repair.

[shadows]

what engine do you have in your Nova
does the carb still have the metal tag on it
does it have a paper or bronze gas line filter

compression gauge on each cylinder will tell quite a bit actually
a little oil squirted in could change things
valves completely seating is another

vacuum gauge readings at idle tells something
vacuum gauge as throttle is blipped tells something

surprisingly- some engine diagnostic engine analizers can give quite good feedback-

feel your thinking correctly- I wouldn't give up on the engine just yet
perhaps you know someone who would come over and dig a little deeper and find out more

of course- you could sell that Nova- some still look for those to hop up

had a freind who dropped in a built 400 small block with Nitro in a Nova
very fast

[Joseph812]

On that last observation first, that might explain why a neighbor's friend wanted to buy it from me. Can't get the title out very easily or access a notary public even if I wanted to sell it, though.

I would have to get a chance to totally remove the air cleaner to answer some of those questions, and I hope to be able to do that within several days or so. I still gotto find the fuel filter location. If it's not screwed into the carb base, could it be in the gas tank or in the fuel line under the car? Maybe once the bottom of the air cleaner is off, I will be able to see it by tracing back the fuel line.

I think the engine is 1.6l. It has the special automatic transmission that locks the torque converter at 30mph if that is what is does.

When I can finally get the car started and it warms up, the idle is super smooth. That says something, but how telling it is I'm not completely sure.

It's still hard to believe it has a computer, though. I see no indication of its existence by dash lights or anything else. The only light I remember seeing is the door open light.

The oil light has long gone off after all the cranking needed for a cold start. I should check again to see if the choke will set. But either way, after it is pretty warmed up, hitting the gas stalls it. At a traffic light, I seem have to power brake it and push the pedal ever so slowly before it can go.

[shadows]

thanks-
sure seems like you should be locating that fuel filter-
continued cold cranking is the enemy to an engine

[Joseph812]

I can see how the oil pump might not be able to build pressure as much during the low RPM cranking and hopefully mine has been good at building the low rpm pressure. Fast idling on a cold engine has given me an uneasy feeling however because the oil has run off the parts when it was sitting and not running. Often heard that starting an engine is when the wear happens and that it was oil dryness of the parts that did the harm which was worse the higher the revving was. Maybe I've been seeing that wrong over the years though.

Definitely can see what you mean -- that to change the fuel filter is a good idea and I saw where it is now and it looks easy to do, so that is one thing I plan to do for sure.

I did tip the air cleaner bottom up and hopefully didn't crack the thick hose restraining it. Saw that the accelerator pump looked like it had a crack in the rubber boot on top -- looks like it indicates a problem. I figure that if only the accelerator pump worked, I could manage because I would be able to tap the throttle to prevent stalling or pump in extra fuel during starting. The failure of the pump could be attributed to alcohol in the gasoline.

Been tinkering with an electric bicycle that I made, too. I added a jackshaft so that the gear ratio that the motor benefits from would be increased. However it needs some extra robustness added to it.

[shadows]

be sure to not remove that gas filter and try to start the vehicle-
no telling what is sitting in the fuel line-

you can have the line loose where you could watch when the engine cranks a few revolutions to see if fuel flows- carefull though- just a few seconds crank will tell you- you don't want much fuel to come out and possibly start a fire- course I've been known to attach a rubber hose and catch some gas in a glass jar- lets you know what your fuel looks like

the real problem with continued cranking is that the cyliners are basically dry- oil doesn't really get up there untill the engine is running good and the crank splashes oil-
and if gas is going in the cylinder and not firing- you really wash the cylinder and the rings can really damaged the walls- to the point you may never get good compression- then the engine needs to be taken apart- worse case- quite a bit of fuel washes by the oil ring and and in the oil pan- checking the dipstick and smelling of raw gas on it is a good sign- may even be high on your dipstick- depending- you could even lock up an engine-
most cases of fuel flooding dictates draining and fresh oil put in-

I'd remove all spark plugs- let it air out maybe even over night- spray some oil in- can even dip a small hose in oil and dribble some in thru the spark plug hole- even WD40 is not bad- and crank it over just a couple revolutions to see what the compresion is- could be real low-

really- at this point you should stop the cold cranking- find out if you are getting much fuel out the end of the gas line- and what it looks and smells like. A good measure of fuel would be 1/3 quart jar in maybe a slow count to 8 as the engine is turning over- if you have electric fuel pump- short time ignition on( like count to 6) should fill that jar 1/3

can you totally remove that air cleaner assembly- bit of twisting the hose or 2 connected should allow it to be removed- get it completely out of the way- will make for much easier checking

a digital picture of what is there and how it looks with that cleaner assembly off would be nice-

take it easy- don't get in a hurry- you're going about it right-

[Joseph812]

Thanks for the supportive comment you gave at the end of your last message.

That bit about the crankshaft splashing oil now comes back to me as the means of lubricating the cylinder walls. It had slipped my mind that there aren't oil outlet ports that spray the cylinder walls.

Now I understand my oversight of the lubrication methodology and will do the starting procedure differently now to reduce cranking time.

I recall from my earlier years how we used to tinker with our late '60s and early '70s model year cars and check the fuel pumps by cranking gas into a glass jar. Just had to loosen the clamp from the rubber gas line and insert it in a jar the way you mentioned and see how far it fills after something like 10 seconds of running. It would run off of what was stored in the float bowl. It would have been safer, though, to pull the coil wire off and ground it and then just crank the engine without it being able to start.

One thing that might help is that it starts hard due to lack of fuel, and one big reason I did extra cranking was so that I could start cranking it first before trying to get much fuel to go into the cylinders in order to prevent flooding because I remember how damaging it is to the cylinders, and I remembered that, once the the plugs are wet with gas, the spark becomes weak or completely gone, and then it has to be aired out like you said, or cranked with the choke and throttle both open to dry out the cylinders.

I think that line of reasoning you had about the fuel not getting into the cylinders covers the most likely scenario, rather than flooding. I did save a couple of peanut butter jars from the days when food more often came in glass. There might be long enough lengths of rubber fuel line going from the pump toward the carb to brace a jar there and direct a freed section into, to check the flow into it. Best to check it after the fuel filter, even, then that might save having to change it right now if it isn't clogged.

Speaking of pictures, it is apparent that the carb was replaced not too long ago since it is shiny where rust hasn't gotten to it already. It's much cleaner than other parts under the hood. I'm a bit surprised that the boot over the accelerator pump rod would have split like that. I have a camera but pictures usually turn out bad because of blurriness.

I might have a chance to check out some more stuff on it tomorrow.

If I can get gas out of the accelerator pump of the carb consistently when I tap the throttle, I think that will be enough to satisfy me that it is good enough for the rare bit of driving that I normally need to do and the rare bit of driving that fits my budget.

[shadows]

I'd like you to back up a second-
that little bit of rubber on the accelerater piston that is cracked really isn't an issue
yes you could slap open the throttle a few times and maybe see a bit of fuel squirt down the carb throat- that isn't really what you should be concerned with- you should check that fuel comes out of the gas line at the carb when you turn the engine over a few revolutions- then that fuel is going thru the filter

quite a few times a fuel pump will supply some fuel to the carb- but unless it is fairly steady- you might get your car to start, idle, and run if your carefull- but if it can't keep a decent fuel level in the carb bowl your vehicle will starve for fuel and leave you stranded

some of those vehicles even experienced a vapor lock because the metal line rested on the hot engine- or was too close

what you want to find out is -are you getting steady fuel to your carb
then you want to find out if the carb is controling the flow- meaning- is the float shutting off that flow before gas fills up the float bowl and runs into the carb throat

you can have any number of problems with fuel-
1-you need to first find out if you are getting fuel to and into the carb- cold and when the engine is at operating temperature
2- if you are getting fuel into the carb, cold and hot- is fuel dribbling into the carb throat body more than just a tiny amount at idle- and at say 2,000rpm- ie- the float must keep the fuel coming in at a level that doesn't cause it to be too high and run into the intake- or too low that there isn't enough fuel to keep above the jets- I'd say without knowing for sure what carb you have- the primary jets could be above the bottom of the float bowl

you could have something as simple as a cracked float- that might not have been spotted when someone took your carb apart- should always check a float by putting it in a container of fuel for a reasonable time-
or you could have float that sticks open or closed- sometimes

I recomend you investigate and not drive your vehicle- you are asking to be stranded- at the least it might restart- you might need a tow, which could cost more than you realize- someone could stop and offer to help- you could end up in a situation that is dangerous- wish you'd reconsider-

you've been thinking pretty good- you have a problem- you ask here on this forum- trying to help you- never drive a vehicle that could stall that you know it might- your life could be at risk

just advice from being a mechanic and owning an auto repair business for quite some years- there is a reason a quality mechanic is really needed sometimes- sort of sounds like you need a good mechanic- instead of looking at why, how come, and what is real cheap to do yourself-
quite possibly you have a problem that is so simple that a good mechanic would identify in a few seconds- issue is- good mechanics don't come to your house very many times in our lives without a fee- there's a reason good mechanics have a job and make good money- some of the best open their own business and are successfull- 90% of the good mechanics aren't parts changers- they are good because they identify the problem and offer reasonable rates to do the work necessary- the best have the knowledge of experience to identify, know what is the right proceedure, not modify but do what's necessary to repair so as to be in line with what is expected of each vehicle, will do the work correctly the first time, and expect to be rewarded with a top job, and return customers

really hard to offer you precise and exact help on the internet as there's a lack of understanding of meaning-

[Joseph812]

I'm with you that breaking down isn't an option at all.

One pertinent thing that factors in is that it has never failed to pull up a hill once I nurse the engine RPM up into the power range.

Kudos to you for the good career you have had.

P.S. The fixing it right part, or I mean the lack thereof, is a big reason why I think the car is beyond economical repair, and really, unfortunately, car ownership is unfordable in many ways for me these days. Yet I believe in personal transportation, and I'm glad the bike can help a lot with that, though it has a lot of limitations, too.

[Joseph812]

A couple of things have occurred about the car since my last post. I have still been contemplating the workings of throttle body fuel injection.

Okay, so the condition of the problem had deteriorated to the point where the car wouldn't even start anymore a week or so after my last post.

Also, however, I have replaced the fuel pump and filter because after trying to start it for another hour or so with still no sign of gas output from the carburetor, I saw that the housing of the pump was wet with gas that had leaked out of it. I was hoping that that would fix the problem, yet it still wouldn't put gas out from the carb into the engine once the pump was replaced with a new one. I replaced the filter as a precaution because it was probably dirty anyway.

So, I remembered back to my young days of having my first moped that wouldn't start and I remember totally blocking the air from the intake to the carb to apply suction to the carb passages. I thought that I had nothing much to lose by doing that on the car, so I took a small piece of newspaper and packed it over the top of the carb, on top of the mostly-closed choke plate.

After blocking off the air intake that way, I cranked the engine starter, and after about two seconds it started! I figure that the vacuum that got applied to the carb passages sucked out the clog. Now, I will see how it does the next time to see if it will still run, hopefully within a few days from now.

There is a recurring problem with the secondary throttle body filling up with gas as I watch the engine idle. I noticed that a month ago, too, when it still ran. Now that it runs again, it still tends to fill up the venturi area as mentioned, on top of the secondary throttle plate. The plate closes with that much of a seal that it doesn't leak into the engine faster than it accumulates, which is impressive about the tolerances of the fit.

Cars are just too complicated!

[shadows]

best you get a good mechanic/carb person to look at your problem