Question about Lexus LS 400
You are right this is a classic MAF problem or rather the air mass meter AMM which is the MAF working with the closely associated intake air temperature sensor IAT(a little bead like thermistor on wire sitting close to the MAFF in the air stream). The ECU was getting poor information from the MAF. The ECU had to rely on slow input signals from the IAT and feedback from the oxygen sensor on the exhaust to keep the engine running. The ECU hunted for the right mix, first rich and then lean but never settling hence the 'surge and slow' of the engine revs. When you disconnected the MAF you also disconnected the IAT and now the ECU had just the one signal from the oxygen sensor to depend on and so now provides a slightly rich mix giving the rough idle. You have done the hard work just change the MAF and IAT assembly.
Posted on Aug 19, 2010
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Posted on Jan 02, 2017
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