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Please check the OBD-1. The first thing to do is to check the OBD-1 early, often, and when you can. Though a sensor of device the OBD-1 can report on may be faulty, yet the OBD-1 may not report a fault.
For example, and off topic, the power stage is a device that may be faulty itself, or you may have connector corrosion, yet the OBD-1 can't detect or measure a fault if so. (For fun, check the power stage to wire harness connector. Dress it with DeOxIt Replace the heat sink compound between the power stage IC amplifier body metal back plate and the aluminum alloy heat sink to which it secures. If corrosion at the two power IC to aluminum alloy retaining machine screws, use some penetrant oil, like a drop of PB Blaster or thin machine oil, let sit, and work the machine screws in and out until they come out. And pull a spare power stage with number 0 227 100 124 is for 240 has the higher [?] output to the ignition coil than does 078]. Find these also on 740 and 940 in the yunkyard.)
Back on topic, you have one of two different throttle position doo-hickeys, as either a sensor or switch, on that Volvo 240 with the Bosch LH-Jetronic / EZK Ignition. The LH-Jetronic fuel control uses the TPS.
Dirt and grime at the wire harness connector can cause some havoc with TPS function, yet the TPS itself may not have a fault.
iPd lays it out all nice n' eazy-peezy for us Volvo 240 eatin', drivin', carin' for them 240 schlubs.
The around $26-$34 (less expensive) TPS, as a throttle position sensor, is part of the Bosch LH-Jetronic 3.1 ignition.
You can tell whether you have the Bosch Jetronic 3.1 as you have manual transmission, no EGR, and the 0-280-217-001 4-pin MAF/AMS/AMM (fix that air filter box flap valve or disconnect the pre-heater hose), and the Bosch LH-3.1 ECU with part number 0-280-000-572 (white label is best! my spare maroon label 572 needs help, tho.)
http://www.ipdusa.com/products/11349/124616-throttle-position-switch
The Bosch LH-Jet 3.1 Throttle position sensor is a potentiometer (variable resister) like that used on the later Bosch Motronic. Fails due to grime and dirt intrusion, so clean it, or fails due to the potentiometer itself failing, so replace it.
And, the more common ....
The around $70 (more expensive) TPS, as a throttle position switch, is part of the Bosch LH-Jetronic 2.4 ignition. This switch is the more ubiquitous version on, I believe, Jetronic versions from 2.2 to 2.4. Or maybe merely the 2.4. (The earlier LH-Jet versions that use an idle air screw have a somewhat different TPS switch.)
http://www.ipdusa.com/products/6780/114719-throttle-position-sensor
This TPS switch is merely a switch. Using your multimeter continuity check across the pins (I forget the pin positions), you have continuity when you close the throttle by removing your foot from the accelerator to engage the idle control (a fault across these contacts at socket 2 is 1-3-3), or continuity across different two contact pins when you press the gas pedal to full throttle (a fault across these contacts at socket 2 is 2-1-3). When the TPS switch fails, some of the copper contact is broken or ends up causing continuity when you drive, or you have dirt and grime intrusion, interfering with contact continuity.
So, as Amarin says, you can prise open the TPS switch at the barbed fitting holding the housing together. Clean it, snap back together, and check continuity. Someplace images of an exploded TPS may abound. (Maybe some DeOxIt?)
A symptom of failure or fault on the OvLoV 240 goes haywire as the idle control engages while you humming down the road, you have no idle, or the engine races (dangerous!).
The OBD-1, socket 2, which is LH-Jet, may take a while to flash the fault codes on a faulty TPS. When I suspected a fault, I removed and replaced the wire harness connector, and voila!, there was the fault. Each time on mine it was a fault with the idle control contact continuity. I rare floor the Volvo 240.
You can grab a few from the yunkyard, test, perhaps open and clean them, and test, to have some spares.
Hope that helps.
Questions?
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