99 Avalon Sensor problem (?)
pinkflydxx
02-21-2005, 02:10 PM
1999 Toyota Avalon
6 cyl
135,000 miles
Car idles and runs fine when first started. However, after running at higher speeds on interstate, car begins to run “rough”. If you take your foot off accelerator, car’s tach will kind of move up and down like it is accelerating and then releases repeatedly. If you pull over, car will do the same accel/decel and feels very rough. After turnign off and letting cool down for a little while, runs fine again.
The “Check Engine” light does NOT come on at any time. The “Check Engine” bulb is working because it comes on briefly when you start the car. Local auto store’s diagnostic shows no codes coming up, but did not actually check when car was running in a “rough” condition. They stated that if the “Check Engine” light is not coming on, code may not present itself.
I believe the problem may be an O2 oxygen sensor, or possibly an Mass Air Flow sensor. However, because it has three O2 sensors and the diagnostic check does not confirm anything, I do not know which it may be, or even if something else it going on. Any suggestions?
6 cyl
135,000 miles
Car idles and runs fine when first started. However, after running at higher speeds on interstate, car begins to run “rough”. If you take your foot off accelerator, car’s tach will kind of move up and down like it is accelerating and then releases repeatedly. If you pull over, car will do the same accel/decel and feels very rough. After turnign off and letting cool down for a little while, runs fine again.
The “Check Engine” light does NOT come on at any time. The “Check Engine” bulb is working because it comes on briefly when you start the car. Local auto store’s diagnostic shows no codes coming up, but did not actually check when car was running in a “rough” condition. They stated that if the “Check Engine” light is not coming on, code may not present itself.
I believe the problem may be an O2 oxygen sensor, or possibly an Mass Air Flow sensor. However, because it has three O2 sensors and the diagnostic check does not confirm anything, I do not know which it may be, or even if something else it going on. Any suggestions?
tfeld
02-21-2005, 06:48 PM
Just guessing here, but it doesn't sound like sensors to me. Sounds more like tranny. The tranny has electronic controls as well as it's own ECU (ETC). On other Toys, I've seen the electronic solenoids go which can do some strange things. But I think you'll need to head to the dealer or someone who really knows what they're doing to dx this.
pinkflydxx
02-22-2005, 04:43 PM
Thanks for the info.
Do you think it still may be the tranny even if this problem continues when I put the vehicle in park or neutral? I will try this the next time it happens and report my results.
Do you think it still may be the tranny even if this problem continues when I put the vehicle in park or neutral? I will try this the next time it happens and report my results.
tfeld
02-23-2005, 07:08 AM
No...that doesn't sound like tranny if it's happening at park or neutral. It also doesn't sound like an O2 sensor since a bad one would throw a CEL.
Here are some other areas it might be related to:
The rubber air intake hose running from the air filter to the throttle body (TB) can be loose or cracked; when you give it gas, the torque on the engine can twist this hose and let air in thru the crack which will screw up the air/fuel mix and make the engine run poorly. You can test this by spraying some carb cleaner on the hose with the engine running--if there's a crack or a loose hose somewhere, the engine will start to run poorly. If there is a crack, just duct tape it well until you can get a new one.
The MAF may be really dirty or bad. It's easy to clean--just remove it and spray it well (but gently) with throttle body cleaner. (There are a couple of platinum wires inside that have to be cleaned--don't touch them at all, but spray them down well). If you have a factory service manual (FSM), you can also check the resistance.
TB may really be dirty--you should probably remove it and clean it out well. A lot of gunk can get trapped behind the butterfly which you can't see and can't clean just by spraying TB cleaner down the throat.
Your Throttle Position Sensor may be bad. Again, there is a procedure for testing this and setting it in the FSM.
I would check these out first.
Here are some other areas it might be related to:
The rubber air intake hose running from the air filter to the throttle body (TB) can be loose or cracked; when you give it gas, the torque on the engine can twist this hose and let air in thru the crack which will screw up the air/fuel mix and make the engine run poorly. You can test this by spraying some carb cleaner on the hose with the engine running--if there's a crack or a loose hose somewhere, the engine will start to run poorly. If there is a crack, just duct tape it well until you can get a new one.
The MAF may be really dirty or bad. It's easy to clean--just remove it and spray it well (but gently) with throttle body cleaner. (There are a couple of platinum wires inside that have to be cleaned--don't touch them at all, but spray them down well). If you have a factory service manual (FSM), you can also check the resistance.
TB may really be dirty--you should probably remove it and clean it out well. A lot of gunk can get trapped behind the butterfly which you can't see and can't clean just by spraying TB cleaner down the throat.
Your Throttle Position Sensor may be bad. Again, there is a procedure for testing this and setting it in the FSM.
I would check these out first.
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