by kjmiller1984, August 25, 2014
On hot days after I start my corolla it will stumble as soon as i push the gas, occasionally it will die completely but mostly just stumble for about 5-10 seconds, then it will take of normally. If I get to a stop sign or light soon after it stumbles again as I try to accelerate, taking 5-10 seconds to get going. It seems once the car is warmed up the stalling/stumbling stops. Any suggestions? Things I can try? I love my little 'rolla and dont want to have to get a new car!
CEL did not go on? Have you cleaned your MAF/IAT sensor on your intake? Have you cleaned your throttle body and checked for obvious vacuum leaks at hoses, intake manifold gasket, etc?
What mileage are you at? How's your maintenance record? How's your oil consumption?
CEL has been on for a bad O2 sensor forever. i havent checked to see if it is throwing additional codes. I have cleaned the throttle body and checked for vacuum leaks. 180k on the mileage. oil change every 3k miles. Oil consumption is weird, first 2500 miles of oil change and it uses nothing, but everytime i change the oil at 3k it is always low by at least a quart.
Bad upstream or downstream O2 sensor? Car will run OK with a bad downstream one, but generally not forever. Though the upstream one is used for majority of the air/fuel mix for driving, both are used to adjust the overal fuel trims.
Couldn't hurt to pull the plugs and see how they look. Could be plug fouling - engine will run very poorly initially until it blows through the fouled plugs, then it runs great on the now cleared plugs. Could be a result of your oil consumption. If you see puffs of blue-white to gray-black smoke come out when you run into these poor acceleration issues, could be oil fouled plugs.
This family of engines are also exceptionally sensitive to electrical noise. A battery that is weak on reserve capacity and/or charging system that is not running 100% could cause this poor off-idle acceleration.
Oil consumption - sounds like fuel dilution. Engine will consume oil but it will be diluted with a higher percentage of gasoline (pretty normal for oil burners) - gasoline will make up the difference between the lost oil - so it "looks" like the car is not using any oil. Eventually you'll come to a certain concentration where the gasoline will rapidly cook-off and sudden oil seems to disappear. Adding a little bit of make up oil will help a lot - a small fraction of fresh oil added to old oil has been shown to boost the additive pack immensely.
For really bad oil consumers (loose 2-3 quarts over a 5000 mile oil change interval) - I keep a track of oil levels every time I drive away, or at least every fillup. Topping off every chance I get - even if the oil drops a couple of oz, I fill it up by that small fraction. About 500-1000 miles before I'm set to change the oil, I'll add a 1/4 to 1/2 quart of fresh oil - always ended up draining out a pretty much full crankcase by the time the oil change comes up.
