What is this strange buzzing sound?
 

I came home today and walked past my SC and heard this buzzing sound coming from the engine compartment. I opened her up and couldn't see where it was coming from but it seems to be behind the air filter. Any ideas what this could be?

The key is off, I assume?

Ambient air valve? Sound like a kazoo? That would be with the car running.

The key is off and the car is not running. At first I thought it might be the blower fan but it hasn't worked since I bought the car. It seems to be in the same area though.

Assuming you have no electrical draw, could it be a depressurization of the CIS going on, via the return line from the fuel distributor? Just a guess...

wasp or bees building a nest?

Seriously, how long ago was the engine running? More info is needed for sleuthing.

that's my vote

I had run the car earlier that morning. When I noticed the buzzing it was maybe around 5 in the afternoon. When I disconnected the battery the buzzing stopped.

i withdraw my vote!

What year if it is an 82? 83 then it could be your frequency valve but then the key/power should be on or the valve is leaking down

Lorne M.

What happens if you remove the power line to the engine blower? I know you said is hasn't worked for years, but it would seem the most likely culprit. Removing its power lead will at least eliminate that possibility. Or maybe remove the blower relay if you know which one it is.

Forward of the heater blower you will find a wire harness with a quick disconnect pull up end (this will be located on the horizontal bulkhead just inboard of the left rear shock). Next time the buzzing happens disconnect that harness by pulling straight up on the connector. That will disable the frequency valve, which I think has probably developed a wiring problem...

I also hear that buzzing sound that come from the engine compartment. It is that FV, is it normal to buzz all the time.

mike

Voila!
 

I did just that today Peter and guess what? The buzzing stopped. So now what? Is the valve screwed or is there a wiring problem? If it's a wiring problem where do I start to troubleshoot that?

Thanks for all your help.

-bryon

Tricky problem that I've never seen! I think that we have to start with the OXS relay under the passenger side front seat. Near the center tunnel (you can find the relay with the seat installed, but slide it all the way to the rear) you will find a small (about 1" square) silver box (relay) attached with a small bracket.

The relay is sold at P-car dealers, part # 821 951 253, I have a hunch we should start there. If you can buy/replace the relay that would be great.

I don't have a wiring diagram for that circuit (I'll look in my library later today), but the harness is pretty bullet-proof. Somehow the system is allowing voltage to pass through into the Freq valve with the key off, and I'm going to have to think about that one!

I disconnected that relay and the buzzing stopped. I think I have another piece of the puzzle as wel. The car has leaked water for some time and I noticed the plug was a little darkened. I am wondering if the relay is damaged or would the entire brain have been affected? The car seems to run without the relay connected btw. I also noticed that the car seems to pull like snot now. Power wise, it's never been better. Any idea why that might be?

Something is really messed up with your mixture! The typical, properly-adjusted Lambda SC (with the OXS relay removed or failed - i.e., non-functional Freq Valve) will have a terrible time with cold starts/running. Without seeing pre-cat CO% numbers taken at idle with a warm/hot engine I couldn't guess as to why the car seems to run that well.

On some cars, under the drivers seat, that would be the fuel enrichment relay that has some control over the duty cycle of the frequency or pulse valve at different operating temeratures and throttle positions. It is triggered by the throttle position switch on the throttle body and controlled by the k-jetronic box.

The other small relay if there is one may be the rev limiter and then the big metal box is the k-jetronic brain that runs some of the temperature sensors, switches, and few electrical parts of the CIS fuel injection including the lambda emission controls that take you back to the frequency valve and oxygen sensor.

Never heard of the frequency valve (which is actually an inline electronic fuel injector being used to bleed off fuel system pressure in the lower half of the fuel head and return it to the tank) pulsing away when the motors off, but if a ground shorted out from moisture getting to the enrichment relay I guess it could happen.

When you disconnected the pulse valve you richened up your overall air fuel ratio a little and the car made more power... probably idles a little smoother too.
A small CO adjustment on the fuel head may make it even better.

You could just accidentally leave it that way if it's not a problem.