Erratic Idle

chash360 · 06-26-2007, 06:55 PM

I would definately try to seal the air leak, I am not familiar with this 'spray test' but if it is leaking, after passage through the MAF Sensor, that is equivalent to a vacuum leak, as far as the computer goes (getting more air flow than is being measured). Do what you can to minimize or eliminate this leak.

Additionally I would suspect the O2 Sensor conversion, if memory serves correct the second wire is just a shield wire, but the operational parameters may not be the same as the stock sensor, and EMI may affect is performance (purpose of the shielding wire). These enignes are heavily reliant upon computer control, everything is manged by computer, including spark timing. You can actually adjust the Cam position sensor out of proper position and the computer will actually try to compensate, and bring the timing back in.

This is also a point you my want to double check. Did you check and adjust your timing with the auto advance turned off? The are 2 connections on the diagnostic plug that you have to short when setting your timing (Cam position sensor). This must be done prior to starting the engine, to prevent the auto compensation. On a typical older car this is the vacuum advance on the distibutor you would plug, but the Supra is all electronic timing, you have to short the proper connection, again I would need to consult my manual, but it should be documented in every manual specific to this engine.

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06-26-2007, 06:55 PM	#12
chash360 Stock Join Date: Dec 2006 Location: Oregon Posts: 14	I would definately try to seal the air leak, I am not familiar with this 'spray test' but if it is leaking, after passage through the MAF Sensor, that is equivalent to a vacuum leak, as far as the computer goes (getting more air flow than is being measured). Do what you can to minimize or eliminate this leak. Additionally I would suspect the O2 Sensor conversion, if memory serves correct the second wire is just a shield wire, but the operational parameters may not be the same as the stock sensor, and EMI may affect is performance (purpose of the shielding wire). These enignes are heavily reliant upon computer control, everything is manged by computer, including spark timing. You can actually adjust the Cam position sensor out of proper position and the computer will actually try to compensate, and bring the timing back in. This is also a point you my want to double check. Did you check and adjust your timing with the auto advance turned off? The are 2 connections on the diagnostic plug that you have to short when setting your timing (Cam position sensor). This must be done prior to starting the engine, to prevent the auto compensation. On a typical older car this is the vacuum advance on the distibutor you would plug, but the Supra is all electronic timing, you have to short the proper connection, again I would need to consult my manual, but it should be documented in every manual specific to this engine.