What the hell is that thing?
 

Left the digicam at work, so no picture...

Just cleaned the engine, and hanging off/near the air filter is a control (I believe a potentiometer) that is marked only "L R" - a screw that rotates about 270 degrees. its screwed in place with two phillips, the control itself is round, about 3/4 of an inch diameter, and about an inch high. The overall size including the mounting bracket is about 1" x 2".

I've spent the last hour looking through the shop manual and Haynes with no look.

Its an 84 GSL-SE...


Anyone have any idea what this thing is?

i can check in my factory service manual and get back with you. a pic would help but i think we can get it sorted out. if i can find it, i'll let you know by tomorrow afternoon. dave

Idle mixture adjustment. Notice that it has some goop in the top that Mazda puts in there to discourage people like you and me from trying to tune using it. I think that step was intended for dealerships, actually...

Anyway, it adjusts idle mixture and is a potentiometer that sends a signal to the engine computer to adjust fuel flow during idle conditions. This has also been referred to as the idle 'gross' mixture, since it has an immediate effect on both idle speed and quality compared to the TB mounted idle speed adjuster(s).

It is recommended by factory and aftermarket manuals not to attempt to adjust this setting, since it can have drastic effects on hydrocarbon emissions from the EFI cars. I have adjusted mine in the past to tune the idle performance and it does have a very definite effect on the idle speed and quality of idle.

L stands for Lean, R stands for Rich, and this adjustment is only necessary if/when you have to replace this part after a failure. It is not used for any other purpose other than for emissions shops to adjust for HCO output during pre-inspection tune-ups. HTH,

Variable Resistor controls the fuel mixture at idle... recapping L D... nice car though L D...

Cool, thanks for the info...I was assuming "Left Right", which just didn't make ANY sense (as far as I could see) for an under-the-hood adjustment....

Its "Lean" and "Rich" I believe ;).

~T.J.