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From the Bosch Automotive Handbook, 3rd edition, Page 444, LH-Jetronic:
"Hot-wire mass airflow sensor
The stream of intake air to the engine is conducted past a heated wire (hot wire) which forms part of an electrical bridge circuit. The flow of current through the wire serves to maintain it at a constant temperature above that of the intake air. This principle makes it possible to employ the current requirement as an index of the air mass being drawn into the engine. A resistor converts the heating current into a voltage signal which the ECU processes along with engine speed as a main input variable. A temperature sensor is mounted in the hot-wire mass airflow sensor to ensure that its output is not influenced by the temperature of the intake air. The A/F-ratio at idle can be adjusted with a potentiometer. As contamination on the surface of the hot wire could affect the output signal, each time the engine is shut down the wire is electrically heated for one second to burn-off any contamination. The hot-wire mass airflow sensor has no moving parts, and its aerodynamic resistance in the intake tract is negligible."
I can assure you that if LH 2.4 is working properly it will maintain a stoich mixture at highway cruise, in any air temperature you are likely to see in the US. If it did not it would not pass emissions testing. If you still don't believe me we can take a ride in my LH2.4 940 with a voltmeter on the O2 sensor signal ;) Or you can borrow my A/F gauge that reads the o2 sensor signal and hook it up to your 240. Just 3 wires to connect.
Furthermore, I ask you this: If the heating the air coming through the AMM is necessary, why is there no mechanism to do this on any LH2.4 turbo volvo? Take a look at your 1995 940 turbo and you will confirm that there is no preheat like the 240 upstream of the AMM.
Eric
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