sfm4103

I have had 3 Toyota mechanics work on this problem and no one can find the problem.

Problem:
Intermittent hesitation (engine misfire or transmission slip?) with normal acceleration, usually between 30 and 50 mph.
Problem does not occur with very light acceleration.
Problem does not occur if I keep transmission in 4th gear instead of drive.
Problem seems to occur more in the afternoon rather than the morning and more often with the AC running (warmer temperatures).
Problem never occurs when engine is cold.
Problem frequency has increased over the past 3 months ago.

95% of the time, the engine, transmission has excellent performance - smooth idle, acceleration, shifting, etc
Mileage:114,000

Replaced plug wires and air filter recently - problem still exists
Changed the spark plugs and cleaned the injectors approx. 10,000 miles ago.
Serviced the transmission, replaced timing belt approx. 18,000 miles ago.
Reset ECU 3 days ago - no change

Any suggestions will be greatly appreciated

JeffTsai

iTrader: (1)

Did you clean the MAF sensor? That's a pretty common culprit for hesitation and rough idling.

sfm4103

Thanks for the suggestion. I'll clean it and see what happens. Where is the MAF sensor located and how do I clean it. I did not see any posts for this for a 99 GS300

sockfocks

iTrader: (1)

check and see if your plastic intake plumbing has a leak or is cracked around the flexible parts. When the engine twists because of torque it could open up a crack and let un-metered air into the engine causing similar symptoms.

sfm4103

checked all plastic fittings in the intake area and can find no cracks or leaks. Still trying to get info on MAF sensor location so I can clean it

sfm4103

do you know of any posts on MAF sensor location or how to clean?

lexluger71

yes plz someone let us know where the maf sensor is on 2001 gs 300

sockfocks

iTrader: (1)

small sensor with wires coming out of it right after the filter location approximately 2-3 inches from airbox. Did you check for cracks while the engine was running? thats how i found one leak on my other car, I moved the ducting around and the engine started changing rpm...

sfm4103

removed the MAF sensor, looked clean but blew out anyway. Should I clean it with liquid, if so what would be best to use. I did check the plastic fittings for cracks again with the engine running, but no change in RPMs. Thanks again for you help.

JeffTsai

iTrader: (1)

Blowing it out won't do anything. You need to clean off the built up dirt, oils, and gunk off of there. Dip a Q-Tip in rubbing alcohol and very gently clean the sensor wire. The MAF sensor is actually in the hole, and not the bulb looking temperature sensor on the tip. Be careful not to put big pressure on the sensor wires, just dab it and rotate the qtip slowly.