My 240 will not idle when started and if you start it without keeping a small amount of pressure on the accelerator pedal it will drop RPMs and stall. I sketchily made a small spacer to the rotating piece connected to the cable going to the gas pedal (for future reference what is that part called?) with the spacer keeping the cable pulled a tiny bit- keeping the engine at 1000 RPMs -the car idles fine although a little high. My question is: should that cable be tight because mine has some play in it. If it should be tight, how would I adjust it, and lastly if there's no way to tighten it would it be a terrible idea to make a slightly thinner spacer to idle lower than 1000 but not so low that it dies?

Sorry if this seems like a strange solution but I'm trying to save money where I can as I'm just in high school.

 

An 87 should have an idle motor. That's an electric valve mounted under the intake manifold that is supposed to control the idle speed. The early ones would get stuck in one position and stop working, or be very erratic. About 2 inches in diameter, with a wire harness plugged on one end and two black 1" air hoses attached on the other. If you have a black knurled **** near the throttle butterfly - that can adjust the idle speed. If it still won't idle fast enough, after cleaning the throttle plate with carb cleaner and a rag, (most people take the three bolts off and remove the throttle housing to thoroughly clean it - but you really should use a new gasket with that method) - you can adjust the stop on the throttle plate with a 8mm wrench and tiny screwdriver to get an appropriate idle speed. If you change the throttle stop you should adjust the throttle switch (although if the idle motor does not work it may not matter) The micro switch in black switch on the throttle shaft makes a clicking when you first open the throttle, adjust it to where it clicks on and off with a small movement. (with the engine off of course.) Obviously put the throttle cable back to being slightly loose, and not pulling the throttle plate open when released.

 

its called the Idle Air Control or IAC in most volvo literature etc. the IAC isn't really a 'motor' per say, its a solenoid actuated shutter.

a 1987 240 uses LH2.2, and yes, has the idle air screw on the throttle, there's a specific procedure to set it up, see below. 1989+ 240s are LH2.4, and the only adjustment is the switch to ensure it closed when the throttle is fully at idle,and opens when its off idle.

the cable should have a slight bit of play at idle.

I would first verify the throttle idle switch is closed when the throttle is at idle and open as soon as you open the throttle even a crack. Then, remove the IAC (have two new hoses on hand), and clean it with throttle body spray cleaner, then use a couple jumper wires to a 12V source, and ensure the shutter inside clicks open/close briskly, and isn't gummed up. reinstall with new hoses, then proceed with the LH 2.2 idle adjustment procedure as shown here...
https://www.volvoclub.org.uk/faq/Eng...#Idle_Problems (read the whole section including on the idle switch adjustment, then pay special attention to the [Adjustment of Pre-89 TB, TPS and Base Idle:]

 

I started out fiddling with the black **** until it idled right around the stock idling RPMs (I had it at around 400 RPMs because any lower and it would idle rough) then I left it for a while to come back and try it without a warm engine and it would work a little bit but it seemed to bounce if that makes sense. It dropped a little and then tried to bounce back up but inevitably it stalled without me giving any gas. Does this help narrow anything down?

 

warmed up engine, all accessories off, in neutral or park, it should idle about 750 RPM. putting it in gear with your foot on the brake, the idle should only briefly dip and bounce right back to 700. that indicates the idle circuit is functioning. ditto switching on the lights, air conditioning, fan on high, idle should remain about 750.

a cold engine will idle about 1200 then as it warms up drop to 750. again, if this doesn't happen, the idle circuit is not working.

the idle circuit is only engaged when that throttle idle position switch is closed, then the ECU modulates the IAC (Idle Air Control valve)to maintain a proper idle.

with the IAC electrical connector unplugged, or the blue-white test connector grounded, the warmed up engine in neutral/park with all accessories off should be idling around 650-700, this is where you adjust the idle air screw on LH2.2 engines. again, this is all covered on the link I gave.