[dohcrxl]

Deal is I transfered an entire chassis/engine harness from a donor 88 crx si into my 90 si 'cause it was stolen and ripped apart. The idle on my d16a6 now surges from 1k to 1.5k when fully warm. I did all the basic surging idle "check fors" and still no resolution. I then checked for continuity from the ECU to the IACV and discovered there was a missing wire in the never before tampered with si harness.

Here's a picture:

The IACV has two wires 1- "a blue with yellow stripe" that goes to ecu pin A11 and a "black with yellow stripe" that goes to ecu pin A17. The wire that is supposed to go to A17 is missing out of the male ecu A-plug. I checked another 89 si that I have and that specific wire is NOT missing. I then looked at a wiring schematic and found that A17 is just a ground that is shared by other sensors including the main relay.

It gets interesting: I then hardwired a ground from the blk/yel of the IACV to A17 of the ECU. This changed the surging idle to a mere but constant 50rpm blip. Here's a picture:

It gets confusing: I swapped out different stock ECUs that I have and they all make the car run veeerrry differently. The pr4 runs flawlessly except for the 50rpm blip. One pm6 hesitates at low rmp and makes the whole car jerk on acceleration but screams to redline passed 3k. Another pm6 runs flawlessly except for a 200 rpm surge.

In all cases, the car returns to the original 1k to 1.5k surge when I disconnect A17.

This lead me to believe that in 88, Honda programmed the pm6 to accept a ground signal for the IACV from the other sensors that share that wire. But in 89-91, the IACV gets its own ground straight back to A17. There's only one thing wrong with this theory and that's that if this is so, the car should run right when I connect the hardwired A17. But... it doesn't.

I think that one of my pm6 ECUs is a 90-91 and I'm sure the other is an 89 which for some reason isn't gettting along with the physical wiring harnesses. I doubt it but has anyone every experienced this?

 

[Synoptic]

I made this for you

for the 1990 - 1991 ecu pinout in the file, it is hard to read it, but you can always use this : http://media.honda.co.uk/car/owner/medi ... 22/6-9.pdf, its the 1990+SiR ecu pinout. it's the same pinout, except for minor changes, like clutch switch, second O2, vtec, pressure switc, ELD and some alternator input. All important devices are conncted to the same pins.

You might want to check for continuity between A18 and the ground on the thermostat housing. This one is a VERY important ground.

 

[dohcrxl]

I dl'ed the file you made for me. When it finished and I went to open it, a window popped up telling me to "click the program you want to use to open the file." I'm computer illiterate so I clicked the first program on the list which was "Accessibility Wizzard." I realize now that that program wont open the file. I think I was supposed to use internet explorer to open it?

Now, everytime I go to click the file icon, it gives me the same message that says "There was a problem loading the file specified when running the Accessibility Wizzard." -thus I cannot change the program to be used to open the file. I tried deleting and re-downloading but that doesn't work either. I think my computer recognizes the file now? Please help.

Also, the link you provided for the siR isn't active. Is it possible to talk me through this? I will check for continuity from A18 to the T-stat ground tomorrow. Thanks for your help.

 

[bluecrxnc]

Reason his link doesn't work: He has a comma at the end of the URL
Here's the same thing corrected http://media.honda.co.uk/car/owner/media/manuals/CRXManual/62sh222/6-9.pdf

Now that you told Windows to use Accessibility Wizard with the .pdf extension it will continue to do so unless you change it. Go here http://ardownload.adobe.com/pub/adobe/reader/win/7x/7.0.8/enu/AdbeRdr708_DLM_en_US.exe and download Adobe Reader. Install and it will automatically associate .pdf with it's program. Then re-open file.

 

[toxiclows]

it is a PDF file... you need to download adobe acrobat to open it...
http://www.adobe.com/products/acrobat/readstep2.html

 

[dohcrxl]

OK so according to the link there is no wire at A17 which reflects my physical wiring. Only, I'm likely using a 90-91 ECU which the wiring harness is required to have and does have a wire at A17. How then do I make this 90-91 ECU work with this 88 harness?

What I'm thinking now is that in 88, the blk/yel is a shared power supply, the blu/yel is a ground fed to the IACV by the ECU to control it?

Then in 90-91 the IACV got a direct power feed from the ECU through the blk/yel A17 wire then the ECU sends a ground signal through the blu/yel A11 wire to control the IACV? If this is the case and I am in fact using a 90-91 ECU, hardwiring A17 should make it work but it doesn't.

What I really need to know now is why A17 is there on later model CRXs and what purpose it serves. Someone's gotta know.

 

[Synoptic]

OK so according to the link there is no wire at A17 which reflects my physical wiring. Only, I'm likely using a 90-91 ECU which the wiring harness is required to have and does have a wire at A17. How then do I make this 90-91 ECU work with this 88 harness?

What I'm thinking now is that in 88, the blk/yel is a shared power supply, the blu/yel is a ground fed to the IACV by the ECU to control it?

Then in 90-91 the IACV got a direct power feed from the ECU through the blk/yel A17 wire then the ECU sends a ground signal through the blu/yel A11 wire to control the IACV? If this is the case and I am in fact using a 90-91 ECU, hardwiring A17 should make it work but it doesn't.

What I really need to know now is why A17 is there on later model CRXs and what purpose it serves. Someone's gotta know.

ELD ?

 

[dohcrxl]

Not according to the schematic I have 'cause its shown with A11 for the EACV. I even looked at the one you provided also and yours shows A17 as part of the circuit for EACV in 88 then in 90-91 A17 is an empty spot. Something is all goofed with these diagrams because physically in the car, it's the other way around... 88 is supposed to have a wire for A17 but there is none in mine.

Besides all this, ELD on 88-91 si is B19. What diagram did you look at that shows A17 as ELD?