Any oldschool obd1 mechanics here i need help with a diagnosis - Toyota Yaris Forums

GeneW · 02-24-2009, 10:48 PM

Could also be the Oxygen sensor, a borderline condition that does not trigger a check engine light but may be deranging mixture settings enough to cause the system to target something else that governs mixture.

There may also be issues with exhaust gas recirculation, if the vehicle has such a device, since carbon deposits may have broken lose and stuck it open or closed. I think most modern cars use an EGR because it reduces pre-detonation and improves NOx emissions by changing the chemistry of the combustion.

Another, more awful possiblity, is that you've compromised oil control by loosening up some carbon around the oil rings and now you have blow by. Easy to check, run the engine hot and see if there is "puffing" when the oil filler cap is removed, in really bad cases the dipstick holder will also "puff" blowby.

Another possibility is that your carbon removal trick has clogged the catalytic converter. You can test this problem by driving the vehicle under load - like up a hill - it will lose power rapidly going up hill. A clogged catalytic converter will cause issues with idling too.

Gene

02-24-2009, 10:48 PM	#19
GeneW Banned Drives: 2008 Yaris Join Date: Oct 2008 Location: Pennsylvania Posts: 1,034	Could also be the Oxygen sensor, a borderline condition that does not trigger a check engine light but may be deranging mixture settings enough to cause the system to target something else that governs mixture. There may also be issues with exhaust gas recirculation, if the vehicle has such a device, since carbon deposits may have broken lose and stuck it open or closed. I think most modern cars use an EGR because it reduces pre-detonation and improves NOx emissions by changing the chemistry of the combustion. Another, more awful possiblity, is that you've compromised oil control by loosening up some carbon around the oil rings and now you have blow by. Easy to check, run the engine hot and see if there is "puffing" when the oil filler cap is removed, in really bad cases the dipstick holder will also "puff" blowby. Another possibility is that your carbon removal trick has clogged the catalytic converter. You can test this problem by driving the vehicle under load - like up a hill - it will lose power rapidly going up hill. A clogged catalytic converter will cause issues with idling too. Gene