240DL stwgn, air flow meter

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240DL stwgn, air flow meter[ALL/1998] posted by C. S. on
Thursday, 31 July 1997, at 5:04 p.m.

I own a 1989 Volvo 240 DL station wagon, ca. 150,000 mile. A year ago we had to put in a new computer (which one, unknown), but otherwise the car has been ok. However, within the last month or two my "check engine" light has come on. The first time the mechanic simply reset it. I drove 70 miles and it came on again. We continued our trip (the car got excellent mileage) and on my return the mechanic checked the error code and said it could be either the "air flow meter", or a temperature thermistor in the air flow meter. A new air flow meter is 500.00. Other than the light, the car is just fine. No rough idle, power and accleration all seem ok, and mileage is good. If it is running lean might that explain the mileage? The car has tended to run hot for brief periods of time when climbing hills, but never in the red, and the temp always recedes to normal as soon as the hill levels off.

So,

do I replace the air flow meter and hope the light stays off?

do I drive until something more obvious breaks, and if so, what sort of damage am I risking (burnt valve?)

can the air flow meter fail, but only at specific air flow rates? I presume the air flow is measured with a hot wire anemometer.

suggestions?

Thank you

Re: 240DL stwgn, air flow meter[ALL/1998] posted by Robert on
Thursday, 31 July 1997, at 11:21 p.m.

C.S.
I would not jump too quickly to replace the MAF sensor. First make sure the electrical connections are clean ( no oxidation ). Route the MAF sensor wiring as far away from the coil wire as possible. This can cause a false code. After driving a while to heat up the engine, remove the air cleaner and check the heat riser flap. It should be in position to draw in cool air rather than air from the heat riser tube. This can also cause premature MAF sensor failure. Your car has adaptive fuel control. If the engine is running lean the O2 sensor will detect it and the fuel ECM will adjust the fuel trim to compensate for for it. If the ECM nears the limit of its adaptive function it will set a fault code 231 or 232. If these codes are not stored or the engine does not run like it is starving for fuel, you should not be in danger of causing other damage. The MAF sensor on your car is a hot wire type. At 150,000 miles it is probably nearing the end of its life, but I would think twice about spending that much money just in an attempt to turn off the light. Also make sure the ground wires at the intake manifold ( under the fuel rail mounting bolts ) are clean and tight.
Good luck,
Robert.

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