Engine sometimes stall at red light

[Broo]

Happened twice this evening. Stopped at a red light, everything looks fine and suddenly engine stops.

Engine is a 1981 Toyota 3A, automatic transmission.

I'm by no mean an expert mechanic but on this car I try to do as much as possible by myself to learn in the process. This is not my daily driver so it's no so much a problem if it's stopped for a few days because I'm repairing something.

Some facts :
Car is driven about 1500 miles a year, never on the highway (going over 50 MPH is downright scary and the engine noise is unbearable at that speed due to lack of noise insulation and high RPM since it only has 3 gears and the 3rd one engages at 30 MPH)
Idle is fine, maybe a little too high, but I won't bother adjusting it unless it's related to my problem.
Stalling only happens sometimes, only when the engine is at normal temp and only when idling.
New fuel and air filters installed last year, along with new timing belt (~1500 miles driven since)
New spark plugs, plug wires and fuel pump installed a few weeks ago.
When it stalls, I slap it to neutral and turn the key, it restarts right away, no hesitation.

Maybe the carburetor ? I do have the rebuild kit and float but I hesitate to tackle this puzzle.

 

[PolarisX]

I feel that if it was the float it wouldn't want to restart easily that fast.

Since you replaced the rest of the ignition I would check the coil and any connections to the distributor / coil. Also make sure you don't have any loose intermittent grounds.

 

[Brent_G]

High idle and stalling would be lean. Check for vacuum leaks as I would bet that there is a hose or something cracked.

80's cars love vacuum lines

 

[PolarisX]

Originally Posted By: Brent_G
High idle and stalling would be lean. Check for vacuum leaks as I would bet that there is a hose or something cracked.


Good point!

 

[JimPghPA]

If it were mine I would try a couple of bottles of a good fuel system cleaner to clean the carb. But the idea of a possible vacuum line leak sounds like it could be the problem.

 

[spasm3]

Are the cap and rotor good? I would put a timing gun on it and check the timing. And like others check for vacuum leaks. Some caburetors would wear and leak vacuum at the throttle shaft.

 

[Electrajoe]

Most of the above fixes, then run out old gas,. Put in a new batch from another station.

 

[Silk]

I'd say the ign module - at idle it goes into current control, dumping excess current as heat. Seeing at the module is in the dist and running at engine temp, it over heats. It'll get worse and worse.

 

[Trav]

Some of these old Toyota's had a vacuum operated dashpot on the carb for the throttle (not the choke pull off), if your has one make sure it hold a vacuum to check the diaphragm, the non vacuum ones can also have a bad diaphragm, push it with the finger and make sure it has some resistance.
A vacuum one with a bad diaphragm will cause a small vacuum leak and prevent the dashpot from cushioning the throttle as it comes down to idle.

Some also used an electric solenoid that only activated at idle, I am not sure what this one uses its been well over 20 yrs since I saw one.
It could be a lot of things already mentioned in the thread, this is just something else to look at.

 

[zrxkawboy]

Good suggestions above. Also, I would check the pick-up coil air gap in the distributor.

 

[EdwardC]

I'm no expert, but maybe the valves need adjusting (if it doesn't have hydraulic lifters)?

 

[JMJNet]

For this old cars, if it has hoses use in the fuel system, they may deteriorate with Ethanol in the Gas.
Those old hoses are not designed to be alcoholic. LOL!!!

Heck, a lot of the new lawn mowing and small engines and boats are not designed to be ethanol resilient.

 

[North to Alaska]

"Maybe the carburetor ? I do have the rebuild kit and float but I hesitate to tackle this puzzle"
Start with the simplest and cheapest. Clean the carburator first.
I am not knowledgeable about carborators but those are signs of a very dirty throttle body.

 

[Bgallagher]

I would suspect a vacuum leak as well. I would get a spray bottle of water and spray down all the rubber components. Look for bubbles or bogging down.

Also, an 81 Toyota 3a still on the road is impressive. Kudos!

 

[Yah-Tah-Hey]

Shouldn't be hard to fix as those engines are very simple. Take the carb apart and soak the parts in lacquer thinner. Don't soak any of the composition parts. I had an 84 Tercel SR5 station wagon with four wheel drive an it was easy to maintain. I believe that had a 3A-C engine but they are all basically the same simple engine. Have you tried resetting the fuel/air adjustments? Float level? Sounds like a low speed idle problem.Fuel pump?

 

[Broo]

Thanks for the pointers guys. I will start with the simplest : vacuum lines. There aren't that many since it's a 3A and not a 3AC (less smog equipment). While working on it, I quickly checked the various vacuum hoses. I noticed a small one which was cracked on the end, I cut this end and reused the remaining hose since it was still long enough. Haven't done the water spray test, will do.

As for the ignition, I have not touched the distributor since the cap looked to be in good condition. So I don't know about the rotor. I should check it out.

This car doesn't see any ethanol with me. However, in order to get ethanol-free gas, I have to buy 91 octane, and only 2 stations around here sell ethanol-free premium. I bought it in 2015, so how it was cared for before then, I don't know. I have some Marvel oil I use for my small engines, could it be enough to clean it out over time or should I use something more aggressive ?

I will try to locate this dashpot device (Haynes to the rescue) and test it. I hope it's good since I saw on Rockauto that these are quite expensive.

Hosteen, as mentioned the fuel pump is brand new. The one I replaced seemed to work fine, but it may or may not have been 36 years old. Since it was quite cheap, I bought a new one as an insurance.

Bgallagher, what's even more impressive is that it survived this far despite spending all its life deep within the rust/salt belt. It may have avoided many winters though, as the mileage isn't that high (a bit over 60K).

The paint and body are definitely not so well preserved though, but it's very good for an early 80s japanese car. Cosmetics will be taken care of next year... maybe.

 

[Broo]

A followup since the trouble seems gone right now. I couldn't find a vacuum leak. I kept replacing some more ignition parts : ignition coil, distributor rotor and cap. That seemed to help a lot. Idle seemed smooth enough, but it's even better now. The spark plugs seem to blacken quickly. The kind of dry black carbon due to mixture being too rich. The carb will definitely need adjustment and/or rebuilding. If the plugs already have carbon, the rest of the engine must be quite dirty. I started to run Marvel Oil in the fuel in hopes of slowly cleaning this up meanwhile.

 

[andyd]

Stuck choke would do this. Or a squirrel nest in the air cleaner. Warm up the engine, pull the air cleaner off the carb so you can see the choke Spray the linkage with something oily and then gently exercise it. Sliding, spring loaded stuff doesn't like to sit. It binds up. The car probably has a lot of vacuum powered smog equipment to pass emissions. 25 yr old widgets