Variable Resistor Adjustment
 

I am curious about the Variable Resistor (VR).

I am leaning out my idle, as it's very very rich. I did all the steps in the FSM (which were very easy) and turned the screw on m VR and it didnt change the idle much.

My reason for this post i simply to ask if my VR should change my idle alot? Or a little. I have no frame of reference for how much it should change things. The cap in the TB changes the idle a ton and i didnt know if the VR was the same way.

I will unhook it and ohm check it later but before I did that, I just wanted to ask.

Did you jumper the intial set coupler first. W/o the jumper it won't change at all.

Yeah. made a wire with 2 spade connectors and plugged them into each of the plugs in the initial set coupler. i did it like the FSM picture showed me. and when i did that, my car started up as if the BAC was unplugged so i'm fairly sure i did it right.

i think so anyway. lolz

Did you turn the screw to full rich then to the complete opposite direction to see if there was any change? I think the position of the idle adjust screw on top of the throttle body plays a role in how much the Variable resistor affects idle although I might be wrong on this. On my car there is a perceptible change related to the resistor setting.

Yeah, i had it both ways. it changed the idle by about 50 to 100 rpm. not alot but more than nuthin'.

The idle screw changes it a ton. right now i have the idle screw almost all the way down/in and the variable resistor is all the way on the lean side, i think anyway. lol.

someone else said to jumper the intial coupler to the negative battery terminal, but the FSM pic has it jumpered into itself.

The coupler on an S4 has 2 wires that are to be jumpered to each other while on the S5 it only has one wire which is to be grounded to the battery.

If the head of the adjust screw is practically all the way down that may be too much. Does your idle hold when coming to a complete stop after a cold start with the screw in this position or does it want to bog down?

It idles like a champ. My main reason for doing any of this was because it just seemed WAY to exhausty. to the point of my not breathing in to avoid it. my other RX7 wasnt that bad, but this one... whew...

I know what you mean especially when my car is in the garage.

So, am I right that the VR leans the idle right?

Yes, and a bit as well throughout the rpm band.

the factory setting is in the middle, so you can make the idle richer or leaner. since you're changing the mixture a little the idle speed won't change much.

so you turn the idle mixture to where the car idles the best. the FSM ( foxed.ca ) has a procedure to set the idle mixture and speed...

since its EFI, the variable resistor will ONLY affect the IDLE. mazda has an idle zone, and outside of that (1100ish rpms or 10%ish throttle) the variable resistor does nothing.

if your car smells, you may want to check the Air Control Valve

That's what I thought until I read the following from Bumpstart,

"actaully the bias is across the entire signal through out the range
but due to the log form nature of the sender output,, the bias is larger at idle than when its at WOT."

if the car is running rich enough, the variable resistor will have little to no impact on how the idle is affected. like if you rewired the fuel pump for example.

love the responses guys. my car is completely stock. When you said the Air Control Valve, did you mean the BAC? If so, I ohm checked it and it's good. I had it check for exhaust leaks, and there arent any. and it runs great. 26mpg, solid idle, no smoke or anything. just really strong.

ACV= Air Control Valve. Located on the opposite side of the engine. Houses a few different valves related to emissions. Air pump connects to this part.

I gotcha. I was thinking of replacing my air pump too.

Have a pic possibly of the ACV?

It's fairly large and sandwiched in between the port actuators and has a couple of solenoids screwed into it along with a couple of black cables.

If i get a new air pump - will it come with it?

Absolutely not, unless you foot the bill for it. They're two separate items.

lol. fair enough. air pump on here are like $25.. is an ACV a lot more?

thanks for helping me so far. i'm learning as fast as i can.

Do you know for sure that you car doesn't have one? If it doesn't then there would be a block off plate in its place. Just use the advanced search function to find of the cost for a used ACV in the for sale forum.


https://www.rx7club.com/search.php?searchid=9073665

as soon as i posted my thoughts, i looked it up and found one for $5.

As for having one, my car is completely stock so anything that Mazda put in it in 1988, it still has.

Then you already have one.

i will dive into the FSM tonight, but is the Air Pump and ACV hard to replace? They seem to be sitting right on top.

You can test the ACV via the FSM rather then replacing it just for kicks. The air pump is just a couple of bolts, one belt, and two hose connections if I remember correctly.

EDIT: To test the ACV though you need a working air pump.