crxmatt

So my idle in my hatch is haunting when the light are on or the heat/ ac,
it idles perfectly When there not on I've replaced:
Iacv 4x and cleaned them all
Replaced tb gasket and swapped throttle bodies
Checked tps voltage
Bleed coolant
Replaced map sensor o ring and idle screw and iacv o ring
Checked the ect
Checked all vaccum lines

This occurred after running seafoam thru my engine a couple months ago
I cannot figure out the problem and I'm totally stumped if anybody has some advice I'd really
Appreciate it, I think I've read every idle thread on the Internet that I could find and
Tried every thing possible in the service manual

Sometimes I get a p0505 while sitting at traffic lights but no other codes except a p0420
Which has been there for awhile and before I run the seafoam thru it

The real Ryan

The factory service manual says to substitute a known working ECU if you have already tested for voltage at the IACV and the IACV it's self tests good. It's a fairly simple system the ECU sends proper voltage to the IACV to regulate the correct amount of air bypassing the throttle body. Try a friend's ecu.

crxmatt

I have tried a different p2t ecu from my friends si with no luck as well unfortunately.

hatchboiracer

just my two cent, check your injectors, they to can cause bad idle sometimes

The real Ryan

His CEL is for a fault in the IACV system and Catalyst System Efficiency Below Threshold (Bank 1) which means front o2 sensor. OP since you have tried everything else, I would replace that o2 sensor and go from there. I know it's not likely that a bad o2 sensor would cause this but you never know and it needs to be fixed anyway. I actually have the same problem but my IACV CEL trips randomly ( it will sometimes go a week with no issues) and I was also throwing a CEL for a front o2 sensor. I replaced the o2 sensor and so far the IACV has not acted up but I just replaced it a few nights ago so time will tell.

crxmatt

Im don't have a code for the primary o2 tho only for the cat I think I'm gonna try and replace my injector o rings next cause it couldn't hurt and many the seafoam at them up

The real Ryan

Well after replacing my faulty o2 sensor the IACV cel came back today. Reset the ecu and continued driving as normal with no problems the rest of the day. It will be fine for up to a week before the cel will pop up again. So scratch that theory about replacing the o2 sensor first. Only thing I have left to try is grabbing a conversion harness and pluging a P28 on there to test for a faulty ECU. Otherwise I'm in the same boat as you no idea what the culprit could be.

93delslow

a faulty 02 sensor will cause surgin idle.as far as iacv.... there are two of the exact same plugs. think black and yellow is one of the wires that is on the plug. check that. a obd1 ecu will hide some problems. stay with obd2 and fix problwms. i am running into that issue. fix the things that causes cel light on with obd2 than convert. but get rywire conversion... haveing problem with that to... hope this helps some...

crxmatt

My idle is the strangest thing I've ever seen some days it idles perfect some days it does whatever it wants to
I pulled off the valve cover and Checked the timing and it's good, checked base timing and fuel pressure and there all good
Anyone have any Other suggestions?

O and my wiring is right I did the 2 wire conversion and the plugs are all plugged in correctly

93delslow

also check your butterfly.. or throttle cable. mine does same thing and i pull up on gas pedal with my foot and isles at 800... but does it purge? like 1500=1000=1500-1000?