Corolla Stalling in the Morning

Hi there, I own a 1987 Toyota Corolla SR5 coupe with an automatic transmission and 88,000 miles on it in San Francisco.

At certain temperatures, it has a problem with stalling as I try to accelerate from a stop. It idles in park or neutral fine, when in motion it drives and accelerates fine. This only seems to happen when the temperature gauge is about a quarter of the way up the gauge- once it is past this temperature, it runs fine (normal driving temp is halfway up the gauge). During these conditions if I absolutely floor the gas pedal it will haltingly cough and splutter for about 10-20 feet then drive fine. Less pressure on the gas during the danger temp means the engine will completely and instantly die, requiring frantic restarting- often in the middle of an intersection. This happens without warning- no warning lights are on, no audible or tactile clues from the engine precede the stall until I hit the gas pedal.

Cold, moist conditions like rain or fog (this is in San Francisco) seem to make it worse but there is no guarantee- it has stalled on warm sunny days and has run fine on cold, rainy days. The only way to be sure it won’t stall seems to be when I try to demonstrate it for the mechanic. This only seems to happen in the morning- parking then starting the car later in the day, no matter how cold or wet it is, does not stall even at the “danger temp.”

I took it to the local dealer, who replaced a “Thermostatic Vacuum Switching Valve” for around $700. However the problem has not gone away, if anything it has gotten worse (this might be due to colder weather.) I sent it back to the dealer again, who now cannot even recreate the problem. I have drowned the engine with industrial grade fuel-line cleaner and carburetor cleaner, checked the air filter and hoses, changed fuel grades and brands, anything I could think of, nothing has helped.

Other than this and a broken air conditioner (in SF who cares?) the car runs fine- can someone help me?

I would suggest finding a mechanic that is old enough to have worked on 1987 Toyotas when they were new.  In that part of the country you should be able to find one.

First of all, it sounds like the dealer gouged you. $700 to replace a vacuum valve? That part is available online for $225, and it probably took them 10 minutes to install it. And, it didn’t even fix the problem. Shame on them.

It sounds like you may have a carburetor problem, possibly a bad accelerator pump inside the carburetor. I don’t know about this particular carb, but the temperature sensitivity of the problem also suggests something like a thermostatic choke that isn’t working properly. Someone who knows carburetors should be able to diagnose and fix this without much trouble. Like Tom and Ray say, find some old geezer. No one under 50 years of age will know how to fix it.

The part was 170, plus 530 for labor. Reason for the price was they were checking over it for several days trying to figure out what was wrong- at least that’s what they said.

Well, don’t ever go back there, because they ripped you off shamelessly and didn’t even fix the problem. Find some old geezer (and I use that term with respect) who knows how to fix carburetors. Your “dealer” clearly does not.

These Toyota’s had a different design of the carburetor to meet emission requirements. One thing they did was to install a smaller accelerator pump, which is designed to squirt fuel into the intake when the gas pedal is pressed. To compensate for an enriched condition when the car is cold, they put another pump on the other side, called the auxillary accelerator pump, or AAP. This pump is controlled by vacuum, and has a thermostatic vacuum switching valve that turns it off once the engine is warm. The common failure is for the AAP diaphragm to leak, causing raw gas to get sucked into the vacuum line when the engine is cold, leading to a super-rich condition causing the engine to stumble. This clears up instantly when the engine warms up, and the valve cuts vacuum to the AAP.

When this happened to my Toyota Pick-up, I unplugged the AAP and capped off the lines. As long as you drive gently until the engine warms up, I never had another problem. The only real fix is to rebuild the carburetor or replace it. Kinda of costly for a 24 year old car.