can you identify this part?

[325iconverted]

87 325i convertible under significant repair.

been reading this forum alot, but this is my first post. I would really appreciate if someone could identify this part so I can replace it. I can't find a picture anywhere in the bently manual.
This part is mounted to the left front of the car, above the brake distributor. It connects with a cable to the accelerator cruise control, and it connects with a thicker (electrical?) cable through the passenger firewall.
It's making a loud, repetitive knocking sound while the car is stopped or moving, engine running or not. Power must be on however. Hitting the brake stops it, or hitting the clutch, but it starts knocking again when both are released. Knocking is faster when the engine is running.

Attached picture below. Here are two part codes that are on it:

1 373 681.9
408201/005/006

Let me know if you recognize this! Thanks!

ps-other repairs I am hoping to attempt soon:
find and fix oil leak
replace front wheel bearing
valve clearance? (scratchy sound in one cylinder)
replace fuel pump

[Fox]

Thats just the cruise control unit. I have no idea what your talking about when you say its knocking but i took mine out anyway because its clumsy looking.

[BMWJNKY]

Your cruise control unit is bad. I see it all the time at work. The reason it stopps when you hit the brake or clutch is cause it interups its signal to be on. Normaly when you drive with the cruise control on if you hit the brake or clutch it will disengage. Just replace the cruise control unit and it will be working properly again, and stop making noise.

[325iconverted]

sweet, thanks!!!! now i'm able to find it in bentley:

"The cruise control system consists of an electronic control unit (located under the passenger-side dash), a cruise control servo (that's it), a cruise control switch on the steering column, and switches at the breake and clutch pedals. The cruise control operates at speeds above 28 mph. The control unit, using the signal from the speedometer, compares the car's true speed to the cruise control speed selected by the dcriver. The control unit then turns on the control motor in the servo to open or close the throttle via a cable. If the driver steps on either the brake pedal or the clutch pedal, the cruise control is switched off."

now, i just hope it's not too expensive . at any rate, I know I can continue to drive arond and not worry about that knocking sound for the time being. Thanks again!

[pogiboy9]

I wasn't all too sure about having Cruise control on a manual :P. Maybe mine's bad too ? i don't think it even engages. removing is just simply unplugging it ? or more wiring involved.

[Fox]

Na removing it is very simple.

Step 1. Remove the cable from the throttle body.

Step 2. Unscrew the module

Step 3. Pull up the wiring, blackwire red stripe (it just runs along a crevise, not hard)

Step 4. Go on the foot well and find where the wire comes in. Behind and above the clutch pedal. Remember its the fairly thick 1/4 inch black wire with a red stripe. Find the plug. Unplug it.

Step 5. This is the hard step. If you want to save the unit to put it back in at a later date your gonna have to slide the wire out through the rubber gromit. Putting the gromit back into place in the firewall is sort of a pain in the ass but whatever. If you dont care just cut the wire and your done in 5 minutes.