'84 240 wagon 400K+. I'm confused. I'm getting some ignition knock when I leave a full stop. I'm thinking the knock sensor is bad. The local Volvo dealer says I don't have a knock sensor. I can't find a listing for a knock sensor online. However my manual (the Bentley) says I have one and there's a wire going out of the distributor loom to something on the block (underneath the intake manifold). As if it were a knock sensor. Do I have one or not? If not, what's causing the knock?

The '84 with Volvo/Chrysler ignition on the B23F motor does indeed have a knock sensor center of the block right under the head and intake manifold. A replacement sensor is hard to find and expensive, but the system does yield to simple testing, unlike the later Bosch sensor (same location as Grey245's image) used with EZ-K ignition.

The test is done with a timing light and a tapping on the block with a small hammer.

I'm recalling someone was able to use the Bosch sensor as a replacement by re-wiring with the two-pin connector. I'd try it if unable to find a direct replacement and it can be proven unresponsive. It is just a crystal microphone.


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Art Benstein near Baltimore

Is it true ants never get sick?
I don’t know, but they sure as hell have anty-bodies.

I wonder how the local Volvo dealer made that determination.
The LH-Jetronic fuel injection system, which has a knock sensor, has been available since 1982. So, an '84 could theoretically have it.

Is there still a sticker on the timing belt cover identifying the engine? If so, what does it say?
If missing or if the cover has been swapped out in the past with one from a different version: have a closer look under the inlet manifold. If you indeed have the LH-Jetronic, there should be two sensors.

I borrowed the picture below from the internet for clarification. The item in the yellow circle is the knock sensor and the one in the green circle is the temp sensor used for the ECU (but not the instrument temp gauge).



The eagle eyed will have noticed straight away that there is a blanking plug where on a 200-series the distributor would be. The 700/900 series have it on the rear of the cylinder head. But for the purpose of this thread, it doesn't matter.

Check your spark plugs / wires and cap and rotor. Hows your timing?

Octane in the fuel too low? Carbon buildup, Timing is off?

+1

Those are 3 good possibilities with an engine that has 400k+ on it. Even if your knock sensor is working it can only overcome so much. You could try refilling an empty tank with premium and also throw in a bottle of Techron Complete Fuel System cleaner to see if that helps. This has helped with pinging/pre-ignition in my high mileage engines in the past. High mileage engines often need more octane to stop pinging and knock.
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Will I buy another Volvo??? We'll see....