rpms bounce when coasting out of gear

[BOSS916]

so i never had this problem until i installed an srs exhaust on my 07 tc. bout a week or two after having it on i noticed that when i would take it out of gear and coast my rpms would drop super fast to idle and then bounce up to 1500rpms. it some times does this repeatedly while coasting out of gear and other times not. i took it to toyota but they didnt know why it was doing this. any ideas why this is happening? any info or advice is greatly appreciated. thanks.

[navylife59]

Sounds like you have a hunting problem. This is usually caused by leaks in the intake, especially around the MAF sensor or a vacuum leak. Do you have an aftermarket intake or oil catch can? Also, do you see this problem when you are at idle?

The SRS is a cat-back setup. If you have an air leak in the exhaust where the OEM and the SRS mate, your O2 Bank1Sensor2 could be detecting the free air. When a motor is rev'd high like on the highway then quickly brought to off-idle, there will be a low pressure area throughout the exhaust system. This draws in outside air which can make it to the rear O2 sensor. The ECM will see this and try to compensate. This "global" low pressure will equalize or tip-in on the throttle will change the pressure state. This can throw a fast one past the ECM and it is unable to compensate fast enough. Remember, the factory tuning is with the backpressure level of the stock exhaust. A DTC may not be tripped for the O2 sensor because it does not fall within the logic structure for DTC's.

[BOSS916]

thanks for responding. yes i do have an Injen CAI. i put it on at bout 15,000miles and i got 41,000miles now. ive been thinking bout checking and cleaning it for awhile now. its probably the intake cuz i havent noticed any problems with my exhaust but im gona check both of them out tomorrow. i will post my results. thanks again.

[navylife59]

Autopart Stores sell a MAF cleaner spray. Carefully take your MAF sensor and clean per instructions. Now you need to re-seat the sensor into the intake boss with a new o-ring. Check all of all of your vacuum lines.