Okay guys. My car has always had the automatic computer in it. It's a p28-a52. The car was converted to a manual (not sure which tranny) and has a d16z6 mated to it. I was looking into buying a manual p28 and just swapping them out but I discovered that the automatic computer can be converted to a manual by removing two resistors on the bored (found somewhere on d-series.org).

I did this conversion and it was successful. I know this because my computer used to throw a CEL code 19 which is for the "Automatic Transmission Lockup Control Valve" and now it does not. It is still throwing a code 14, however, which is for the IACV. I took it off and cleaned it last night, and put it back. I'm still getting a 1k RPM + idle and fluctuating occasionally (800-1200 RPM). The only way I can get it to steady out AND idle in the correct range is to kick on the A/C and headlights, and the idle varies based on whether the condenser fan is on or off.

I disconnected my battery when I took my IACV off and cleaned it, and the computer is still throwing the same code after the fact. Any ideas?

 

Can you replace it with one you know works? You might just have a bad IACV and cleaning won't fix it.

 

so really your problem has nothing to do with the ECU conversion? you had a code 14 before the conversion?

you need to test the IACV circuit. The sensor itself could be bad or there is an open wire somewhere. check for voltage at the IACV power wire (ylw/blk). also check for continuity between the two IACV pins, should be 8-15 ohms i believe. dont have the helms handy

did you ever get the timing squared away?

 

IF the ecu you are using was not for that motor, then the IACV maybe bigger, or the tune maybe different hence the idle issues.

OBD2 IACV is bigger than OBD1 on a B18C5 running a OBD1 ECU for example.
therefore you need to adjust the duty cycle on the IACV in the tune.

dunno about D series sorry

 

the car is running a factory ecu so there is no ability to tune the IACV. i'm not convinced there are different "sizes" of iacv. there are different bolt patterns but as long as they match, i've never had any issue with swapping between all types of IACVs

 

I don't know if it was throwing code 14 before the conversion or not. It always threw code 19 since I had it and that had to do with the transmission conversion. I never bothered checking the other codes.


I believe I've got a spare IACV off my parts car laying around somewhere. I may try and hunt it down and clean it then swap it out and see how the motor performs.

The IACV that is currently on the car came off a skunk2 d series manifold I bought, and when I first put it on (over the summer) the car idled better than every before. But over the past 6 months its gotten worse and now it's back to where it was before I swapped them out.
I did however get the timing set right mechanically, but the ignition is still off. I'm getting a sputter/miss under 2k rpm when I open up the throttle. New plugs and wires are coming soon. Firing order is right according to the service bulletin.

 

Cleaned both the FITV and the IACV today, reset the FITV, adjusted the idle and it runs so much smoother. I disconnected the battery when I did this to reset the ECU today, and I actually swapped the IACV with one out from my parts car (95 civic ex sedan, manual tranny from factory), cleaned it thoroughly with brake parts cleaner, and installed it in place of the old one. The ECU is still throwing code 14 for the IACV now. I checked while the car was running and it is putting out a strong 13+ volts from the yellow wire that plugs into the IACV.

I am not sure how to measure the resistance, however.

 

sounds like there is a broken wire or short between the ecu and iacv, i believe its pin a9 on the ecu. you would need to use a multimeter to check for continuity in the wires

i had the same issue once and just ran a new wire from a9 direct to the iacv but that was when i was lazy and didn'y really know how to use a multimeter.

 

Do you have a link on how to test the iacv circuit? And pinouts on a p28/obd1 ecu?

 

I found the pinout writeup on line, but I have no clue on how the hell to determine which plug is plug "A" and which direction to start counting in haha.

 

iacv is definitely a9 on obd1 ecus. i do not have full wiring diagrams though.

 

Yeah lol. Maybe somewhere like phearable.net would have it.

 

Well, new development. Haven't had time to pull my ecu again and check the wiring, but today my car started developing a slight miss. Only happens at idle every couple of minutes, and occasionally when I'm cruising in 5th gear at about 2k RPM. Im thinking my idle is a little low, so I may back out the screw seat in the fitv a little bit more. Currently the car idles what I would say is about 650 rpm when warmed up.

 

You were only suppose to remove 1 resistor, and use a jumper in place of the resistor

 

How did u get ur code 19 to go off that is the only one mine is throwing an it is also a converted p28 automatic ecu? Tried to find it on d series.org but no luck...any help would be appreciated thanks

 

Blacksheep, here is the picture of my converted p28. I removed the r17 resistor and put a jumper in place of the resistor at r18



Bitcdawg, I found the write-up for this information here at d-series.org:

http://www.d-series.org/forums/diy-f...28-manual.html

 

Awesome bro i appreciate it