Carb problem?

[serpentaria]

I've been taking this out on a lot of dirty roads/light 4wd trails lately, and I've noticed that after about 3 - 4 miles of driving on these dirt roads, my carb or throttle starts sticking. Last week this happened as I was coming home from a camping trip. Luckily, I had some Carb Spray and it seemed to release most of whatever was in there.

Today, I was driving on the dirty roads doing a little light 4wheeling, and the same thing happened...So I did the same thing but it kept on hesitating. Whenever I would open it up, it would be fine, but whenever I would de-accelerate, even slightly, it would start to kick. Accelerating from stop was a hassle, requiring me to continuously rev the engine and let up on the clutch repeatedly, i.e. pumping it, until the first gear sync. 3/5 times the car would just die, and I had to start it up and try again. It idles beautifully.

So, I am still thinking that it is the carb/throttle, but I could be wrong. Could the heat have something to do with this? It has been around 100 the past couple of days/today. Is the dust from 4wheeling mucking up my carb? Sorry for the all the newbie questions...

[dlb]

i don't think it's dirt affecting your carb. i think that the problem was probably just not as severe initially and coincidentally went away when you sprayed carb cleaner in the carb. it sounds like it's a vacuum issue that has gotten worse over time.

the throttle positioner (aka TP) is a likely culprit. it sets how slowly or quickly the revs drop on deceleration. the TP is at the base on the front of the carb, check the emissions controls section of the FSM for a diagram on where it is. then check the TP's diaphragm first by leaving the vacuum hose attached to it and disconnecting the other end from the metal vac lines. suck on the hose and then plug the hole of the hose with your tongue. the diaphragm should hold vacuum. if it doesn't, that's probably the problem. if it holds vacuum fine, then follow the procedure in the FSM and set it to spec. that's my two cents.

[overs10ded]

Sounds like vapor lock could be the issue from the heat. My Tercel was vapor locking a couple of weeks ago after I bought it and drove fine except for my temps staying way too cool MOST of the time and suspected a bad thermostat....finally after one day of fighting the vapor lock I bought a new one and found that there wasn't a thermostat in the car so since then it has been perfect even on hotter days.....maybe your thermostat is worn out!

[xirdneh]

Sounds like vapor lock could be the issue from the heat. My Tercel was vapor locking a couple of weeks ago after I bought it and drove fine except for my temps staying way too cool MOST of the time and suspected a bad thermostat....finally after one day of fighting the vapor lock I bought a new one and found that there wasn't a thermostat in the car so since then it has been perfect even on hotter days.....maybe your thermostat is worn out!

I'm confused?
if your running COOL because you have no thermostat
how can lack of HEAT cause vapor-lock?

[ARCHINSTL]

The last time I had vapor lock was in the '88 Dodge/Mitsu P'up in 2010. The engine temp has always been normal. Now, the root cause was that I was stil on a tank of Winter-blend fuel and it was a hot day in June. But - the heat of the engine compartment is what caused the lock - not the water temp.
I've never had vapor lock on the Terc - nor did I ever have it on the then-new '83, despite some scorching road trips and in urban gridlock as well.
Tom M.

[serpentaria]

The carb was mucked up, which is starting to make me wonder. I ended up pouring a shot glass worth of Seafoam and I let it sit for a couple of days. But what I don't understand is why is my carb getting mucked up all the time? Is this from it sitting previously? But then I'm thinking that it can't be because when I first bought the car, I took it to a carb guy bc I needed it running quickly. He ended up charging me (kinda embarassed) a little over $300 for "rebuilding" the carb, and although it held its own for awhile, I'm wondering why this thing is getting clogged so much. It seems like every time I go on some short 4wd trail, rock and dust, I'll start to get these issues.

On a better note, I purchased some 14" corolla steelies, with pretty much brand new tires (only been used one season). They're snow tires, but with my bedouin lifestyle, I can't be hauling around two sets of tires with me. They look good. Not going to put the plastic wheels covers on. I think the black steel meshes good with the darker siding on the car. (question: When I bought the car, I ended up getting 7 tires. I'm keeping one 13" for a spare. Obviously, if I get a flat, I'm going to need to replace the tire, but I could use it as a temp spare w/ the other 14" on @ the same time?)

Also, I'm thinking of either going two routes as far as cooling. (1)either get the AC converted/charged or (2)tint windows. I'm thinking the latter because its going to preserve my interior a bit also. The windshield replacement sucks, and wish it didn't cost close to $200. Maybe I'll just get everything else tinted for now. Any opinions/advice?

[ARCHINSTL]

As far as wheel compatability goes - I pondered the same thing when I got 14" Miata Daisys two years ago. I kept a 13" for a spare, since the circumference of the new 14" tires I chose was 99% the same as the OE sized tires; the difference is negligible.
Tom M.

[Petros]

The spare tire issue is not a problem, rolling dia is the issue and short distances on smaller tire is no problem.

Have you changed your fuel filter? if there loose rust and crude in the fuel tank, rough roads break it loose and it fills up the filter and you get restricted fuel supply. This allows it idle fine but will stall out on heavy demand (hard acceleration and up longer hills). If the car sites heavy particles fall out of the filter element and the car appears to act "normal" the next day.

Replace the filter and inspect the old one, back flush into a pan and see what you get out of it. If lots of large flakes than I would remove the hatch under the rear carpet, remove the fuel gauge sender and inspect the inside of the fuel tank with a flashlight (careful! no open flames or sparks!). If the tank is badly rusted consider replacing it, if only a few loose flakes you can drain the tank from the threaded plug, wash out the flakes and replace the plugs. there are some repair shops that can boil out a rusty tank, and than coat the inside with a fuel proof sealant, usually cheaper to replace the tank, but worthh checking out if you can not find a new tank.

You can just keep replacing the filters until you catch all of the loose flakes, but if your fuel tank has lots of water trapped in it, you will keep getting flakes until the tank rusts through.

BTW, replace the filter with a Corolla one, it costs half as much as the Tercel filter and is larger.

[ARCHINSTL]

Petros' thread on the Corolla filter:
https://tercel4wd.com/forums/viewtopic.php? ... ter#p51127
Tom M.

[serpentaria]

Yeah, I changed the filter about 2 months ago, but I'll probably check it again for symptoms, and change it with the Corolla filter. I treat every 3rd tank with STP Gas Treatment. IDK if that helps at all. My guess is, it is the fuel tank because the car always runs much smoother with a full tank. My reasoning being that as the crud concentrates as the tank runs down, it'll start to pass the crud in the fuel filter, carb, etc... Is my reasoning off? Would acetone or some other strong solvent help clean out the fuel system? Maybe 99% ISO?

[dlb]

if you have a rusted gas tank, the only long term solution is to remove it and treat it (you can google this, it's a big job) or replace it. you can keep changing fuel filters but they will keep getting clogged--no additives will break down the rust or other large stuff that will clog a filter. at least with these cars, fuel filters are ridiculously cheap and easy to replace.

i'm not sure that that's your problem though. as petros mentioned, fuel starvation due to a clogged filter or fuel lines tends to manifest as bogging down on heavy demand but you said

Whenever I would open it up, it would be fine, but whenever I would de-accelerate, even slightly, it would start to kick.

but you also said

Accelerating from stop was a hassle, requiring me to continuously rev the engine and let up on the clutch repeatedly,

so i'm not sure. for the cost, you may as well replace the filter and see if that fixes it again for a few months. if it does and the problem comes back, you know the problem is in your gas tank. if not, you will need to look at your carb and the vacuum systems. did you check the TP yet?

[Petros]

It is easy to inspect the fuel tank through the sender hole that you access under the little hatch under the carpet in the back of the 4wd wagon, under the rear seat in the 2wd Tercel. So verify you do not have fuel starvation.

However the symptoms could be a messed up carb or a bad vacuum leak, or misrouted vac lines (which can act like a vac leak). If the vac lines are routed correct, and there are no obvious leaks, than you have to check the components than can act like a vac leak: the charcoal canister, the vac advance, the brake booster, the HAC and the mixture control device.

Not likely the carb is causing it unless it was off and someone messed with it and did not realize they left something important out of it.

[overs10ded]

Sounds like vapor lock could be the issue from the heat. My Tercel was vapor locking a couple of weeks ago after I bought it and drove fine except for my temps staying way too cool MOST of the time and suspected a bad thermostat....finally after one day of fighting the vapor lock I bought a new one and found that there wasn't a thermostat in the car so since then it has been perfect even on hotter days.....maybe your thermostat is worn out!

I'm confused?
if your running COOL because you have no thermostat
how can lack of HEAT cause vapor-lock?

Let me explain, without the 'stat, for the most part the car ran too cool as the thermostat is designed to maintain engine operating temperature and to reach it quickly as possible. Without the thermostat or with a stuck open 'stat, the engine takes forever to warm up because the water pump just keeps pushing the water through without the 'stats restrictive properties. But once the engine is heated up, then overheating can occur because the water is moving too fast through the radiator to cool down the water...especially without a thermostat at all!!!! Hope this helps!

Good times!

Bruce

[Petros]

... But once the engine is heated up, then overheating can occur because the water is moving too fast through the radiator to cool down the water...especially without a thermostat at all!!!!

Not sure this can ever happen, the water would also be moving through the engine just as fast. Never heard of such a novel idea before, the problem is more complicated. The t-stat also directs coolant through heater (the reason for the extra metal disk on the end of the plunger of the t-stat), without it in place the coolant direction is uncontrolled and it is unclear what effect it would have. But allowing unrestricted water to circulate through both the radiator and the engine should result in over cooling. I drove a Tercel with a stuck open T-stat in Colorado in Jan, darn thing would not warm up and there was no heat to defrost the windshield. I have also driven other cars without a t-stat at all, it resulted in over cooling and forever to warm up.

[overs10ded]

Yep, I had same experience in Colorado in my youth in the winter! And didn't do anything about it until that summer when the thing started overheating on a regular basis after finally warming up while 4wheeling in the mountains on hot days...after changing the 'stat only, the problem disappeared. That was on a '69 v8 Ford Bronco. The stat was stuck open upon removal, and proof of the diagnosed opinion of months previous.

On my Tercel the day it started vapor locking, I got out and opened the hood, reached around under the air cleaner to work the throttle lever on the carb and burnt the %#**& out of my finger...left a blister even. Then I knew it was hot enough to boil fuel. Anyhow after I put a thermostat in where there was not one, it has run great since. Although the heater core did spring a leak the other day and I bypassed it so now using A/C to defog the windshield and trying to decide what to do about the heater core.

Good times!

Bruce