86 Sport, emissions removed. Otherwise stock.

So I was trying to fix my hesitation issues by grounding the pressure sensor as prescribed by the TSB.

I'm supposed to ground the brown wire with a black stripe (BrB). Slight problem, I don't have one.

There was 4 wires on the plug. Two of them were black (white stripe and, I think, brown). Didn't really pay much attention to those because I wasn't supposed to.

Other 2...

Brown, white stripe, black rings about every 3/4".
Brown, pink (faded red?) stripe, black rings about every 3/4".

IIRC, the black were on the top of the plug (near the connector hump) and the brown were on the bottom.

Ok, neither of those are Brown with a black stripe as far as I can tell. Am I missing something blatantly obvious?

 

I've a 86 and two 87. ALL have a brown/black wire that is ground.

88 models went to a pure black wire for the gnd wire.

The gnd wire should be on the top row next to the Black/White wire.

Black/White......battery voltage

Brown/Black.....gnd wire

Brown/White.....five volt ref voltage

Brown/Red......output from the sensor to the ECU pin 2B

 

Ok, I guess one of the black wires was actually brown then. So... the blatant thing is that I'm blind.



Thanks again Hailers.

 

OK, I looked again. 2 are definately black, 2 are definately brown...

 

Covered here as well:

http://www.aaroncake.net/rx-7/grounding.htm

I believe that I pulled my wire colours and locations directly from the FSM.

 

"Locate the ground wire (this is the brown/black wire on '86-'88 cars, and the black wire on '89-'92 cars) "

I have a black wire with a brown stripe (I think, I'll look tonight)... is that the same as a black/brown wire?

Edit: 86 Sport

 

Yes. The first colour is always the primary colour, second colour is the stripe.

 

You say "brown/black" in your write up (same as Hailers).

If that means, brown with black stripe, I don't have that.


Also, in my last post I meant to say

"I have a black wire with a brown stripe (I think, I'll look tonight)... is that the same as a brown/black wire?" Instead of black/brown

Which, from what you said about colors, is not. Sorry for the confusion.

 

The plug should look like the jpg attached. BrB in the upper right hand corner. Pure black on your car probably.

For some reason you don't seem to be recognizing the STRIPE on the brown or black wires.

The Black/White is 12vdc

Pure black (BrB on 86-87) is gnd.

Brown/White is five volts ref voltage

Brown/Red is the output to the ECU and Boost gauge.

Virtually all those BrB wires are ALL spliced together in the EM harness and terminate at pin 2C on the ECU where they get grounded evidently THRU the ECU to the gnd terminal on top of the rear rotor housing.

I read the factory service bulletin and it said the extra gnd was added because of a problem with the AFM. Since the gnds are all mechanically spliced together inside the EM harness, they used the easily accessible gnd wire at the boost/pressure sensor. Make sense? Got me. That didn't fix my hesitation on my 87 n/a (now turbo). Eventually I found the gnds at the ECU and soldered an extra gnd to them about six inches up the EM harness from the plug and terminated it at one of the studs that hold the ECU bracket in place. By removing that gnd I can make my hesitation come and go at will. I leave it connected all the time.

That said, this does not work for other people who've tried it. Seems to be a hit and miss thing. The extra gnd at the boost sensor certainly didn't work for me.

IF you have two black wires in the upper corner socket, it would sound to me like the factory already reworked your harness. That fix was only for early 86-87 cars, not later.

 

I do wear glasses, but I can see stripes... Like I said, I have an 86, so it should be BrB, which I don't have.

Have that.

Don't have that.

Have that.

Have that.

I don't have two black wires in the upper corner socket (or do you mean "sockets"?). I have one which isn't solid black, IIRC. It's black with a brown stripe.

I'll check again in a few hours when I'm off work. Maybe I'm just seeing them wrong, which I hope. If so, that'd make things alot easier. But... I don't think I am.

 

Maybe your '86 is one of the early models that had the little differences like the coolant overflow tank located in a different place, higher center console, etc. It could be possible that the wires are slightly different as well. I have one of the early models so I can check to see what color its wires are if you want..

 

Sure. My overflow tank is on the driver side front corner. Is that an indicator?

 

Yup, mine is too. I'll try and check those wires after I get home today..

 

Thanks a bunch.

Hailers:

If my car was already fixed by a dealership, there would be an additional wire spliced in near the boost sensor. Correct?

 

I looked at my connector again.

B | B/W
------------------
Br/W | Br/R

So yeah, the wire that's SUPPOSED to be Br/B is just B.

Considering this is an 86... is that indicative of something? Such as, it's already been "fixed". There's not an additional wire spliced in anywhere that I can see.

 

sorry I didn't get back to you yesterday.. long day at work. Anyway, for what it's worth, again I have one of the early 86's with the coolant overflow tank on the driver's side and the wires coming from the pressure sensor are as Hailers described:

 

You could always take a multimeter, and check the readings on each of the wires :-P

That'd be the easiest way of checking which wire is which..I've learned the hard way, NEVER trust the colors the FSM references too. They change practically mid-year it seems, per state (California models, anyways), and different country (Canadian model..)...

 

I did.

B: 0
B/W: ~12
Br/W: ~4
Br/R: ~2

So, my B is what's supposed to be Br/B. I'm just not sure why...

 

Regardless of what people here will tell you, mazda changed some of the wiring colors during the years. The only thing in the manuals that can be relied upon is the pinout position on the plug, not the actual wire color.

I used to try this "fix" back in the day and I personally never saw it fix anything. ITs cheap and easy and one of several grounding points you can try. I have found the TPS adjustment has more to do with the hesitation than the pressure sensor in my own experience.

 

Kinda what I figured. Thanks for clarifying though.

 

Here's a silly question...where is the pressure sensor? What does it look like?

 

It's a small black rectangular box (rounded sides) on the passenger side (U.S. spec) firewall bolted to the strut tower.

 

Back from the dead. I ground the black wire and everything seems good. I remember Kevin telling me when he rebuilt my engine that it appeared that there had been a previous engine swap done. So, I'm guessing that the wiring harness was switched at that time.

I'll take a pic of my awesome (humor ) ground later at some point. I put it on the UIM for now until I can find a bolt that fits the water pump (there's an open threaded hole). I think M8 x 1.0 for reference.

 

just don't ground the B/W wire like I did by accident (doh!) because I was sloppy and didn't meter the wirse. It blew a fuse that I apparently missed when I checked the fuse box the first time, so I thought I had fried my ECU or something until a couple weeks later i double checked the fuses and fixed it.

 

I had every other wire in the FSM except the Br/B and did have a plain B (98% of the time a ground). Unfortunately I didn't have the hesitation yesterday prior to the new ground (it comes and goes). I guess only time will tell.