OP continues thread here: https://www.brickboard.com/RWD/volvo/1653268/220/240/260/280/lh10_rough_idle_saga_continued_chuckles_inside_volvo_240_chrysler_distributor_white_cap.html

Hi,

I'm not so familiar with a LH 1.0 but I own a K jet '78 and jump to an '84 LH 2.0. I then go to LH 2.2 '86. Since then I have moved up to the LH 2.4's of the '91 through '93.
The K jet use an auxiliary air valve that gets heated electrically to mimic the engine warming up and it idles up and back the engine.
The whole K jet is mechanically runs by fuel pressure and an oxygen sensor
for Lambda emissions. The controlling part is done via a frequency valve that pluses all the injectors continuously to adjust mixture.

I tell you this so you can understand what the electronic system is doing as it pulsing all the injectors opening time much in the same fashion.
The IAC now controls idle air, per a preset rpm instruction in the ECU brains.
It's rotating a vane about a quarter turn to widen a gap for air to pass.

On all these systems, all the air, for idling purposes has to go through a control vane, period.
With this said, the throttle plate has to be all the way shut!
That adjusting screw, that you saw paint on, is only a safety stop so that the plate itself doesn't get stopped and jammed tight in the bore opening. So at best, it barely cracks that plate to be open.

Now on the early LH's and your 1.0, you have a left over black knob on the throttle body. This is a small air bypass valve that allows you to get the engine to barely lope at the lowest idle speed possible. This was done before the auxiliary air valve on the K Jet was trimmed in to mimic a cold engine needs and adjust itself down in RPM as both warmed up.
Both air controls have a range of operation and require adjustment to dial them in. The K jet was set to the engine and today's LH's IAC is set to the computers capabilities.

This same knob is used in conjunction with the blue grounding wire to barely get the engine to lope!
The blue wire closes or isolates the IAC out of the loop of the electronic control.
In this mode you will have the engine stifled. This stifle, is the beginning of low end of the IAC's controlling range.
On a properly working IAC, it will take over control of the idling when you remove the blue grounding wire! If the throttle plate is to wide, the IAC Is out of the picture!
When ever you start the car from that point on you listen for the engine to start and rev up above its normal idle speed and then drop back to the preset speed program in the ECU mentioned before.
If it does not do this either the IAC is bad or you have air getting around it to create over speeding!

Air can come in around everything, if the brake booster is letting air in from the cabin or brake pedal side or the hose to the check valve. Yes, even a check valve can have a cracked housing.
If you operate the brakes it usually raises the idle or will make it stumble.

As far as you not having a throttle switch this is unusual as how does the ECU KNOW that you are wanting to idle. This loses me as I have no experience with the LH of the 1982 vintage.
On other LH's it tells the ECU to are going to take off as well. So it give the ECU a heads up to transition over to running down the road programing.
The only vacuum valve that I'm aware of was one to raise up the idle speed for air conditioning.

As far as the spark plugs and the "resistor part" was for a radio and TV interference suppression system. You use to get a popping sound on your radio of your car or in houses along the street. It also made flicker lines across those black & white cathode ray tubes!
We are talking 50&60's here. We could tell what neighbor just got home from work or school.

The spark plug wires are also part of controlling spark radiation with resistance and the wires are made with various schemes to accomplish this same feat!
During this time, the ends of the wires, went through individual makers and experimentation.
Before then, the earliest engines used flat metal strips with a hole in the ends and those were screwed to the spark plug and back to an ignition coil.
The open air surrounding them made up their insulation or later it went on to a thick woven cloth!
Only nice thing about them, a farmer could look and see if he has a bad ignition wire. Not so today!

Spark plugs, stateside, slid away from an open threaded stud but rather to the hub profile you are talking about because a new synthetic rubber coated wires were invented.


What you need to watch out for is the type of wires you buy to have the proper ends to fit whatever plugs you buy. Some brand plugs give you options to adjust their ends. The Wires do not!
Some wires from Europe utilize ends that allow the studs to fit up inside a brass connector with a spring clip. Our older Volvos came with these and heat resistant metal covers down by the exhaust manifold. Today silicone is suppose to replace them or they go to high temperature plastic sleeves.
There is always the backup woven fiberglass sleeves that have to be used on the Chevy Big Blocks!

Inside the push on clip Designs the USA always used a looser fitting made of tin or maybe a fake brass metal clip.
To me I perfer the screw connection as it cuts down on the gap from the top of the plug to the conductor of the wire. The conductor is folded back up alongside the outer shell of the wire and crimped. To me, it has always been a lame setup or call it plain ... cheap!

Now go back to those spark suppressing conductors, that create their own resistance, because of use of carbon or graphite impregnated fibers. You must have to lose something to gain suppression. Most of the time all you got was two years out of them as the carbon shifted or fell apart inside.
It's never made sense to me of its worth of using that junk especially for the last forty years!
Our electronics have moved away from a chassis with hand wired components to solid state board and integrated components. The solid wiring, by themselves, acted like antennas going both ways!

Any how you got short of a book trying to get this stuff down.
I hope it helps!

Phil.