1979 - 1983 AMC Spirits and 1978 - 1983 AMC Concords > '78 - '79 AMC V8 304 Engine

What is this sensor?

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I have a 304 in my '74 Matador wagon.  When I put it in the air, I noticed some things, so I thought I'd ask here.

These pictures are of the same sensor, on the passenger side exhaust near the starter.  What exactly does this sensor do? 
The small loop is flopping around, which makes me wonder if it's functional.  Everything seems to operate just as it's supposed to...

I also noticed the bottom of the canister filter by the washer fluid bottle.  Is it missing something?   ???

Thanks in advance for your advice and insight.

Medina,  OH

The first 3 images are of the manifold heat riser. When cold it partially blocks the exhaust and deflects hot combustion gases into passages in the intake manifold. It results in better vaporization of the incoming fuel-air charge until the coolant heats up enough to take over the task. By that time the heat riser should be completely open and allow exhaust gases to pass through unrestricted.

The coil is a thermostatic spring that winds and unwinds according to surrounding temperature. It is what operates the heat riser.

You should be able to move the heat riser up and down by hand while the engine is cold. If it doesn't move spray some WD-40 or similar product on the shaft where it goes into the exhaust and work it by hand until it rotates freely. The shaft sticks through on the other side of the exhaust. Spray both ends.

I'm not sure what the other device is, so I'll defer to someone else. :eagle:

Looks like you got the answer to the part I wasn't sure of.  

The canister is part of the emissions system and connects to the gas tank vent among other things.  It appears from your pictures that it is missing the bottom.  

My SX4 canister looks like it was glued on with RTV.  I am not sure if that was a P.O. applied aftermarket option or if it was factory.   Mine is detached and dangling at the moment.  On the list of less critical fixes to take care of since I have everything plugged for adjustments.  I looked at it breifly in disgust and it seems like it was supposed to have two/a few clicky tabby-poos that hold it in place that have been broken off.  Not sure if it served any purpose other than to seal the bottom off.  Maybe someone else can chime in on that.  

I understand about the manifold heat riser and the flat thermostatic spring-- but what threw me off was the smaller ring-shaped loop to the right that's extremely loose.  I'm not sure if I should be concerned about that or not.  It seems like it's just dangling there.

Also, should I be hunting for a new "bottom" for the canister?  I'd like to keep everything functioning the way it was designed if possible.


I'll venture a guess and say that it's a return spring of some sort, or at least what's left of it.  Where it attaches and what it is suppose to look like fully intact I am not sure.


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