You are here:

Toyota Repair/1991 Toyota Camry stumbling


I have been asked to look at a 1991 Toyota Camry for a friend. It is the California version, with two oxygen sensors, and it is the 4 cyl engine. The car sometimes runs ok when cold, but as soon as it warms up at all, it starts stumbling and coughing as though it is running out of fuel. The car will idle fine, but under load, it bogs down. I am not getting a check engine light. The spark plugs, distributor and cap are new. Fuel filter and air filter have been changed. I can locate no vacuum leak. The throttle position sensor appears to check out fine.(It is a switch type, and seems to work.) I did unplug the oxygen sensors, one at a time, then both, and the car did not run differently. I think thtey may be bad, but did the O2 sensors in this old of a car adjust fuel trim? What did they do? The MAF is mechanical on this car, but if I unplug it, it runs really bad and I get a check engine light, so I think it working.
Any guidance to can give for things to try is appreciated.

This year still used the OBD 1 system although the front O2 sensor sent a feedback signal to the computer it did not adjust fuel ratio very much, in other words it's parameters are very narrow compared to todays air/fuel ratio sensors. I think I would check to make sure that the moveable door in the air flow meter moves freely all the way open and that there are no leaks in the intake hoses between the throttle body and the air filter.  

Toyota Repair

All Answers

Answers by Expert:

Ask Experts


Ted Ritter


I have more than 28 years experience as toyota technician, I will be able to answer most questions related to the Toyota product line up to the present year models,I am located in the US but welcome questions from other regions of the world. When asking a question please provide specific information: year,model, engine,transmission information. Provide as much information as possible including a brief repair history if possible. I have been a volunteer here for more ten years an have answered over 16,000 questions helping Toyota owners with their problems and save thousands of dollars without any compensation, some of my answers are published on many other websites including google and various automotive forums. DONATIONS ARE VERY MUCH APPRECIATED, IF YOU HAVE RECIEVED HELPFUL INFORMATION PLEASE MAKE A DONATION. AS OF TODAY (JULY 22, 2014) ALL REQUESTED GRAPHICS, ILLUSTRATIONS, DIAGRAMS, PHOTOS, WILL REQUIRE THE MINUMUM DONATION UP FRONT.


Toyota technician since 1979,expert in electrical systems,OBD systems,engine repair, driveability problems,EFI systems,ASE certified,Toyota master technician.
Certified Hybrid Vehicle technician.

Toyota master technician, ASE certified in eight catagories, Hybrid vehicle certified. Toyota technical training: Engine Automatic transmission Manual transmission Drivetrain Electrical systems Brakes and chassis Air conditioning Engine performance and diagnostics Hybrid systems

©2016 All rights reserved.