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Originally Posted by SoCal LS-L
Ok, now correct me if im wrong, but isnt one of the reasons that the ECU needs to know how far the throttle is pressed in for the purpose of timing advance??? Acceleration depends on ignition timing advance, without a proper TPS reading, the ECU wouldnt know when to advance the timing to provide more power, hence the problem with major delay when he presses the gas pedal.
Am I alone here? I mean its not a hard test to do to check TPS operation..........
From what ive been taught, for a distributorless ignition system, the ECU relies fully on MAF/MAP for mixture, and Crank/Cam + TPS sensor readings to calibrate advance, THEN adjusts fuel trim via O2 readings
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Chris Ignition timing advance has more to do with the amount of air in the cylinder, and this is obtained from the Mass Air Flow. Throttle position is really secondary.
The engine will still accelerate, even if the spark does not advance, maybe not as well.
It's the amount of fuel/air in the cylinder that is ignited that accelerates it.
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If the TPS is telling the ECU it should be in idle mode, which would have the IAC valve open..... then he steps on the throttle..... if the TPS is faulty the ECU would not know to advance timing AND would make the engine run lean since the IAC would not shut until the TPS returned a voltage indicating the throttle is pressed. That would cause his hesitation AND a misfire, and could also explain an O2 code.
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No it is the MAF that measures the amount of air that the ECU injects fuel for. The IAC does not introduce any other air, it all comes through the MAF, so it won't run lean, regardless if the IAC is open or closed.
Harvey.