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98 Ls400 Low Idle


Jarebear

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So yesterday I cleaned my MAF sensor with electronic parts cleaner and now my car is idleing particularly low, I reset the light by pulling the battery cables. Maybe the computer is relearning the idle? Any takers?

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Yea I pulled the code, that's why I cleaned the sensor, it was p0172 rich, I cleaned it and the light has stayed off, even with the idle, sometimes it'll idle normal and sometimes it'll idle lower, both when warm. Maybe air intake valve?

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Take at look at the OBDII fuel trim values for long term and short term. They may offer a clue.

An air leak in the intake ducting or the intake manifold can play havoc with idle. It introduces air that is unmetered (leaky air isn't detected by the MAF) so the computer tries to compensate with lean/rich trim by looking at the primary O2 sensors.

You can do the unlit proane torch trick to see if you have leaks. Do it outside though.

Alternatively if its a cracked duct or ruputured tubing it might be quite audible. get a 2' length of hose holding one end near your ear (not stuck in your ear!) and move the other end around to suspicous places. You'll hear a whistling sound of air if there is a decent sized leak.

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Hello Jared,

a few months ago I cleaned the MAF sensor and throttle body on my MK IV. When I bolted it all back together the revs were way too high. However, after driving around for a few miles in stop and start traffic making sure to shift from Drive into Neutral and Park a few times the revs settled back to their normal level.

I am no expert but I think the Throttle Position Sensor has to reset itself after the airflow has been changed.

I hope this helps.

Steve.

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