1990 Volvo 240 only runs with maf disconnected

[JumpinJack]

I have a 1990 Volvo 240 (LH 2.4) that runs with the mass air flow sensor disconnected, but not with it hooked up. I found i have very low voltage on the MAF at terminal 3 (.4 volts). I'm looking for any help trying to figure out what's going on!

[Monkey Wrench]

i tried a MAF from the rock place, it worked ok, the bosche one was very expensive.
it ran better, but a bit lean, still idled a little rough so I adjusted the A/F mixture screw,seemed better.

You can try to clean the contacts well as a first step, maybe the contacts are dirty.

I cleaned one and then read on the can not for a heated MAF sensor , and it is heated.

some say the air valve gets stuck and reverts to pulling air from near the ehaust manifold possibly damaging the MAF, you can be the judge but its a thing to look for.
to the best of my knowledge the 740 shares the same MAF.
a radical option, find carbs intake manifold a low pressure fuel pump , old style distributor, and revert to carbs from an early 240, , ditch the ECU and its complexity. less power, but greater reliability. Its a trade off.
a 1990 probably has the code reader and the TDC sensor, some slight improvements from the 88 or 89 versions.

my 740's share a lot of similar parts to my 240 not everything. same engine block etc. great cars !

worst part to change in a 240 is the heater blower motor. the rest was very sensible. tail lights are generally poorly designed and unreliable despite volvo building safe cars. the printed circuit bulb holders were progressively worse as years progressed. the bulb sensor warnign system is usually problematic. I use the reflection from a nearby store window to check them ocsaionally. if you change bulbs change both sides. if you want the warnig lamp off well good luck, it is possible.

if you pull the MAF plug its probably runing in a sort of "get home mode" perhaps ignoring the O2 sensor.

if you look at the fues, unhook battery , 2 screws and it comes away about a foot or so, then you can clean all the fuses wires and fuse holders. fuse holders fail easily get burned spring tension becomes weak due to the metal loosing spring tension from the heat.

when cranking the speedo or tach shoudl pulsate, if it does not check the TDC sensor out, they can fail or wire deteriorates. to verify ignition pulse I put a small bulb across the coil then crank, the bulb will pulaste during cranking and then will glow dim if it starts. if the bulb pulses you have a pulse at the priimary coil. you should.. no pulse or no fuel at the fuel rail car wont start.