I plan on dynoing soon. So to be absolutey on the ball I reset my TPS, Idle speed and Idle Mixture. Eveything Is going good 'til I adjust V.R. It doesn't budge the Idle, with engine on ofcourse, so I end up disconnecting It and pulling out my Multimeter.

A-C: supposed to be 0.5 - 4.5 actual 4.6
B-C: supposed to be 0.5 - 4.5 actual 11.3

Both of them fell out of spec. Besides this, everything Is good. Should I replace the V.R considering I want accurate results come dyno results? I am aware that the V.R effects Idle only. Also, will be getting S-AFC In near future. Will the AFC take care of the potential "faulty" V.R?

 

ooops. I made a mistake. Disregard please.

Have you checked to see if the blck wire is grounded and the brown and white wire has 5 volts on it??? I'd measure the voltage at the ECU pin 2f and see if you getting input to the ECU and if you do if it is varying when the screw is turned.

I've noticed if the plug is pulled, the ECU defaults to full rich at idle.

The thing does sound out of spec though. That 11 whatever is out in left field.

 

Maybe the VR is turned all the way out in either dir,
which may give you out-of-spec readings. I would turn the VR so that you are midway between full L and R, and then check the resistance.

just a thought,
hugues -

 

As far as adjusting it goes, you have to have the initial set coupler jumpered for the ECU to do anything about adjusting it. All it is is a simple resistor, though.

Dale

 

I can turn the variable resistor, on either of my cars, without the initial set coupler installed, and the variable resistor will make the mixture go rich or lean depending on the direction of the turning. Same with pulling the plug on the variable resistor without the initial set coupler installed. The mixture will go full rich. Just FYI

 

I do the same with adjusting and no initial set coupler, and it also adjusts mine. I can't see why it would matter if the plug is jumped or not, since it's just adjusting the resistance between two points. And the only way to get mine running the one time was to unplug the connector JUST after the car started. Required two people, smelled like gas REAL strong, but at least it got me home from the Mazda Dealer.

 

RestoTII........yo, I've got one of those wideband 02 sensors and I've seen the reading go from a setting of 14.2afr to 12??? afr when the plug was disconnected while idling. Thats pretty rich. Thats running without a airpump so the 02 won't be confused by injected port air.

About the only good a initial set coupler seems to do on a 86-88, is to kill any feedback to the bac so the idle won't rise and fall from outputs from the ECU to the bac while you set the timing. Hmmmmmmmm. From what I just wrote the same could be said about the variable resistor. If you enrichen or lean the idle, there could be feedback from the ECU to the bac which might result in a rise or fall of the rpm's. Oh well.

 

That Is actually a good point and a point I did not Include. Oops. Even still, I did do just that but no cigar.

 

I always jump the Initial Set Coupler when adjusting Idle Speed, Idle Mixture as per FSM directs you too. I did In order TPS>Idle Speed>Idle Mixture when this confusion started.

 

I am primarily concerned with the out of whack specs I provided with the V.R. With It being In milli volts that Is enough to raise concern with It being way out of range!

To pay $174 can for a new one Is a big turn off.

But will the S-AFC be able to "mask" the V.R's malfunction?

 

pin 2F of the ECU shows voltage from variable resistor as seen by ECU. Specs are 1-4 V depending on the screw setting at the VR. This is really what matters IMO.

Hugues -

 

I missed the millivolts in the post. Where was the reference to millivolts??????? Millivolts is like a virtual open.

A junk yard will sell one for less than ten bucks.

I really agree with HUGUES. The first time I used the pages out of the CONTROL UNIT part of my 87 fsm, I wrote in pencil next to each item what I found. Next to the variable resistor I wrote 2.6v. That was several years ago. One to four is one to four.