I've noted recently that there seems to be some wiring differences between the '88-'89 Si's and the '90-'91 Si's...

For example, A17 is the EACV along with A11 on the '88-'89, but it's blank on the '90-'91s...

B2 is the tandem valve control solenoid valve on the '88-'89, blank on the '90-'91s...

B3 is the A/C clutch relay on the '88s, but it's the Fast Idle Valve on the '90s.

B10 & B12 are crank angle sensor wires on the '90s, but they're both blank on the '88s...

etc, etc, etc...

Could this be important? My car DOES have a weird running problem, and I've heard of other cars with this problem too.

 

Here's what i have on my mitchell repair at work:

1991 crx dx
A-17 :blank on 90 91. goes to jumper connection on 88-89
A-11:eacv on all (88-91)
B-2:tandem control solenoid (90-91)(88-89) same
B-3:a/c compressor control on all (88-91)
B-10 Blank on 90-91blank on 88-91
b-12:shift lock control on 90-91 blank on 88-89
How is your car running now? i remember you disconnected your o2 sensors a while back. Did you try replacing your o2 sensors? I am in the process of getting a b-16 in my rex.If i'm not mistaken you do live in canada? The wiring may be different. HTH see ya later.

 

Car's running alright, except it always runs rich... sometimes goes to full lean at part throttle and stays there unless you give it more gas. I just don't understand it . The O2 sensors are still disconnected, and raising or lowering the fuel pressure affects mileage but doesn't change how the car runs. I think I'm going to try switching the pins between the two O2s like people have suggested... thanks for checking those pinouts for me

 

What do you think that an O2 sensor does? Do you think that it needs to be hooked up? hmm

 

Don't get your neckhairs up... basically, the problem when I hook the O2 sensors up is that a pair of cylinders leans out to the point of detonation during part throttle. Disconnecting the O2 sensors solves the problem. The car runs EXACTLY the same otherwise if they're connected or disconnected.

That's the problem... it's like the air/fuel ratio coming out of the engine isn't dependent on anything, including fuel pressure (which should obviously affect the ratio, but doesn't).

 

I only have a 1 single wire o2 sensor on my B16a rex, and i have no problems. Whats all this talk about a second o2 sensor? I thought that was only in post OBD cars?. My current setup is a 91 CRXsi with a PW0 ecu, and the stock wiring harness. The car runs beautiful. Please give more info on the second O2 sensor.

 

I've only got a blurry pic of the dual O2 sensor setup... sorry, no digicam. But here it is:

As you can clearly see, two O2 sensors in the downpipe, one for the #1 and #2 cylinder pair, one for the #3 and #4 cylinder pair. I'm going to try swapping the O2 sensor pinouts today (actually using the O2 sensors), and see if that changes anything . It would be nice to not have a CEL!

 

Did you wire in the second sensor? or what? i'm using a B18a header with single sensor, and like i said, no problems whatsoever.

 

Also, i'm using a PW0

 

The sensors were both connected initially. In order to solve the detonation problem, I disconnected both sensors from the ECU, but left them connected to the air/fuel ratio meter. I have a toggle hooked up so I can switch between the two sensor outputs whenever I feel like it, so I can still see what's going on.

Rio, is your ECU chipped? I've determined that the ECU (mine, anyway) will only detect the lack of the O2 sensors if you've just done a WOT run up to about 4000 rpm, then just leave it in gear and let it compression brake for about 5-10 seconds... sometimes it'll throw a CEL if you leave it in gear to compression brake (as in when you're going down a mountain) for about 20-30 seconds. I've completed an 800-kilometer roadtrip in a single day without the computer detecting the lack of O2 sensors. If you're not running a chipped ECU try doing that and see if it throws a code 2 for the secondary.

Anyway, I just switched the outputs for the O2 sensors... secondary pinout into C16, primary into C8, and it works PERFECTLY now . Hallelujah! Best 10 minutes work I ever spent...

But it still idles rich .

 

No, I just have a stock PW0. I have never ever run into an O2 sensor code. I compression brake, highway, you name it, never any code. Plus like i said, the car runs and idles fine. What i was trying to ask you, is did your car come stock with 2 O2 sensors (i dunno since its a canadian model ) or did you wire in a second sensor? I wasnt even aware that the B16as had 2. It might be possible that the cars equiped with the PW0 ecu only had single sensors, thus my lack of a code. Also, whats your milege like?

 

No codes? Interesting.

Yes, the B16A came stock with 2 O2 sensors. Far as I know, ALL B16As came with two O2 sensors. See if I can find some info for you on it...

Another pic of the 2nd O2 plug wire...


About halfway down under "Now how about some wiring?" is mention of it... also, you can see "Primary O2 sensor" (pin C8) and "Secondary O2 sensor" (pin C16) in the wiring table.

On the HASport site under "Electrical Differences" they mention the 2nd O2 sensor...

I could find more but I'm sure you believe me . The Canadian versions of the CRXs are pretty much the same as the US... only 1 O2 sensor. You're typically supposed to add a wire for the 2nd O2 sensor, which I did with shielded wire.

Mileage for my car is usually about 400km's to a tank at ~39psi fuel pressure. I don't know what miles/gallon that corresponds to, since we buy gas in liters up here. With the stock D16A6 I was getting ~350km's to a tank, so there's no problem there .

 

Crazy stuff. Maybe its my PW0. My ecu is fine, and does throw codes for bad sensors, so that isn't it. Who knows.