Previa LE 1993 - 235K Miles - Hesitating when put in gear

[mihoang]

Hi Everyone,

Hoping someone might have some insight for my van...
My Previa LE 1993 has 235,000 Miles on it and still runs great up until this month. When I put in gear (R or D), the engine hesitates really bad – when I press the pedal and accelerate, the engine starts stalling, and runs not smooth at all.

Clean Throttle Body, Mass Air Flow & Idle Control Valve, also changed the Fuel Filter, Throttle Position Sensor, Distributor Cap & Rotor, air filter, new battery. But the problem is still there.
Any suggestions would be really appreciated! Thank you very much

Feb 1, 2016 - mihoang from California

[Kurtanius21]

Did you check the ignition timing? You replaced a lot of parts. Maybe the timing chain has worn enough to disrupt timing in some way.

what cleaning agent did you use to clean the maf and IAC? It's very important to use the specific cleaner, not one size fits all.

Any burning smells? Maybe a head gasket leak is causing unwanted contamination in the cylinders. Do you see any bubbles in the coolant overflow tank when the engine is running (only check when engine is cold)

oil looks clean? No milky coolant in the oil?

Does the van behave any differently as the engine heats up, or does the problem persist at any engine temp? Leave the car in neutral and turn on the AC. The AC should put a load on the engine. How does it behave then?

[mihoang]

Thanks for your advice, this problem is not easy to find and i am working on it.

[Kurtanius21]

Also consider a bad oxygen sensor. Oxygen sensors play a big part in controlling fuel levels at idle

http://www.simple-car-answers.com/Bad-Oxygen-Sensor.html