IAC and high idle after swap

Natoe · Post by **Natoe** » Wed Feb 22, 2006 6:33 am

all the wiring is completely done, ej22t in my 95 impreza, ive driven it and it pulls great at 9psi, runs really smooth, but has a messed up idle.

the idle bounces between 3k and 2k... it slowly falls to 2k then will bounce up a few hundred rpms, over and over... it even does it in gear if i decel too low in rpms.

ive searched a ton but cant figure it out.

the middle wire on the IAC is power, 12v correct? there is something weird that makes the IAC valve get hot even if i havent ran the car... only when the battery is plugged in. im getting the correct voltages for the IAC for the open and close ends, but cant test the power since it doesnt go to the ECU. (i used my 1.8L plug and so it has power from the same spot as before, since the plug is the same.

i DID take my TPS off, but i put it back in spec.... on the laptop scantool, the "idle switch" is ON until i give a couple mm of throttle it goes OFF which i assume is correct.

also, does it matter if i dont have coolant going to the IAC? when i blocked it off for a different setup, i forgot to hook it back up, but im assuming its like the throttle body and it isnt NECESSARY..
no difference between manual and automatic IAC's?

any ideas? thanks!

legacy92ej22t · Post by **legacy92ej22t** » Wed Feb 22, 2006 1:12 pm

I think you should have the coolant lines hooked up. It keeps the IAC from freezing and/or getting sluggish.

I had really weird idle issues after my swap too but they eventually went away and smoothed out. I also readjusted my TPS and that seemed to help a lot.

In terms of the electrical, I'm no help there, sorry.

vrg3 · Post by **vrg3** » Wed Feb 22, 2006 2:31 pm

Natoe wrote:all the wiring is completely done, ej22t in my 95 impreza, ive driven it and it pulls great at 9psi, runs really smooth, but has a messed up idle.

Remind us -- what ECU are you using? What's your wiring harness consist of? What IAC valve are you using?

the middle wire on the IAC is power, 12v correct?

Correct.

there is something weird that makes the IAC valve get hot even if i havent ran the car... only when the battery is plugged in.

Something's a little weird there... Is the same true of other things like the ignition coil pack or the purge control solenoid?

i DID take my TPS off, but i put it back in spec.... on the laptop scantool, the "idle switch" is ON until i give a couple mm of throttle it goes OFF which i assume is correct.

There's a more precise spec, but that should be the right ballpark.

also, does it matter if i dont have coolant going to the IAC?

Yes, it does. The IAC valve's static position is determined by the temperature of the coolant flowing through it. With the coolant lines not hooked up, it'll always act like the engine is cold. This may be a large part of your problem.

no difference between manual and automatic IAC's?

Not on turbo models.

Your throttle cables aren't too tight, are they?

Natoe · Post by **Natoe** » Wed Feb 22, 2006 11:32 pm

thanks for the detailed reply, ill have to take off a bunch of crap again to fix the IAC coolant lines, but ill definetly do that.

its a 93 turbo ECU, 1.8 engine harness, except i kept all the MAF/boost stuff connected to the legacy ecu, cut the wires off of the 1.8 ECU and spliced the corresponding ones to the legacy ECU.

the IAC gets hot, and for a while the O2 sensor was hot as well while the rest of the engine was cold, not sure about purge or coilpack. (does this have something to do with my self-shutoff control diode thingy?)

for the TPS, i did the .7mm its has continuity, and at .9mm it doesnt, so i think its good enough atleast.

the throttle cable is fully closed.(had to ghetto rig by drilling the hole bigger for the end of the cable but its perfect)

thanks again! must be the coolant lines, they go from the water pipe-IAC-TB if im thinking right.

vrg3 · Post by **vrg3** » Thu Feb 23, 2006 3:00 am

By "gets hot" you mean it has power supplied to it, not that it's reaching high temperature, right?

I suspect it does have to do with your self-shutoff control diode thingy. Can you tell me exactly how you did it? In the meantime you may want to disconnect the battery when parking for a while to keep it from draining.

I do think the coolant lines are largely (if not completely) responsible for this problem. They don't have to go through the throttle body necessarily, but do run them through the IAC valve.

Natoe · Post by **Natoe** » Thu Feb 23, 2006 3:34 am

by getting hot, i mean that they they are acutally hot to touch... the O2 sensor got too hot to touch, while the iac was just pretty warm...

what i did was i added the diode between the self-shutoff and the backup power supply. dont remember which end went where, but i think it only turned on one way...

it did not work connected to the ignition switch.

maybe the backup power supply has 12v always? instead of being ignition switched? are there any other ignition switchd wires i could try?

vrg3 · Post by **vrg3** » Thu Feb 23, 2006 3:41 am

Well, the oxygen sensor is supposed to get hot -- it has a heater. But the IAC valve shouldn't. I guess maybe when the ECU's off it allows current to flow, so maybe the valve is stuck on. Ooh, that's not good for the valve.

Yes, the backup power supply has +12V always. That's why it's there.

Try the ignition switch again. If it doesn't work, then we'll have to figure out why. Connect the cathode of the diode (the end with the stripe) to the self-shutoff control wire. Connect the anode to the ignition switch wire.

Natoe · Post by **Natoe** » Thu Feb 23, 2006 4:10 am

yeah i knew the O2 sensor can (but still shouldnt), but the iac was definetly hot

i just called my dad to have him disconnect the battery since im at school now, its been plugged in for like 36 hours though... i can certainly tell you that i tried both ways with a diode on the ignition swich, multiple times and the ecu was not getting power (no CEL with ignition on) maybe its the diode im using, i dont know much about them but i think it was a 3A

vrg3 · Post by **vrg3** » Thu Feb 23, 2006 4:21 am

That diode should be fine.

So you need to figure out why that wire is not at +12v when the ignition is turned on.

Natoe · Post by **Natoe** » Thu Feb 23, 2006 6:43 am

i havent metered it, ill do that, it might have just been me being stupid and incapable that caused it to not work like it should have.
thanks for your help, ill post when ive gotten to work on it

555BCTurbo · Post by **555BCTurbo** » Thu Feb 23, 2006 7:21 am

Hey Natoe...I live in Monmouth (go to WOU)...we should meet up sometime and check out each other's rides!

Let me know!

Natoe · Post by **Natoe** » Thu Feb 23, 2006 7:43 am

PM'd you!

vrg3 · Post by **vrg3** » Thu Feb 23, 2006 3:22 pm

Heh, well, I'm guessing you may have had the wrong wire or something, which is why I'm asking you to try again.

Natoe · Post by **Natoe** » Thu Feb 23, 2006 9:48 pm

im sittin here with the TB and breathers and intake stuff off the turbo, and this may be a silly question but does it matter which way coolant flows through the IAC or the TB? the only way i can do it without taking off the intake manifold is like...... water supply---TB left---TB right---IAC right---IAC left---water pipe or wherever it goes. (left being drivers side)

it may seem a little backwards but the way i have it this would be most simple even though it looks like it would flow coolant backwards through the IAC. thanks

for the ignition switch wire, its solid yellow, not smaller gauge (bigger) like the other power wires, im sure i had the right wire. i WILL however try it again once i get her to idle right.

vrg3 · Post by **vrg3** » Thu Feb 23, 2006 11:56 pm

No, I don't think it matters.

The ignition switch wire is green-with-yellow-stripe on some cars -- airbag models, I think.

Natoe · Post by **Natoe** » Fri Feb 24, 2006 4:01 am

crap, well i fixed the coolant lines.... and it still did the same idle thing. maybe just because i didnt burp it good enough and there was air there? i dont know i got it to 200degF, i think it may be something else, but its got to be the IAC still.

for "timing advance" on your scantool, its 18ish at idle, when i free rev it like jumps to 50!

under boost it pulls back to 15ish though, is that normal?

vrg3 · Post by **vrg3** » Fri Feb 24, 2006 4:12 am

It'll take a little while to get all the air out of there, since it's kind of a high point.

That 18 degrees -- is that in gear or in neutral? In neutral it should stay at a steady 15 degrees. In gear it should bounce around 15 but can vary around to as low as 10 and as high as 30.

50 degrees of advance when free-revving is normal.

Natoe · Post by **Natoe** » Fri Feb 24, 2006 5:28 am

15 or 18, i was just guessing, but all those numbers were not in gear just sitting and free revving, driving around it would still go up to like 40 with light throttle, but WOT it went back down in the teens.

IAC should be like 40% once its idling right correct? its at about 20% right now i believe.

ill top it off with coolant, and run it again tomarrow to see if it gets the air out. i ran it for 15minutes today though...(didnt burp it though)

vrg3 · Post by **vrg3** » Fri Feb 24, 2006 2:26 pm

Check again -- make sure timing is fixed at 15 degrees BTDC when idling out of gear. If it's not, check the neutral switch.

Yes, the IAC duty cycle should be somewhere around 30%-45% when the engine is idling warm, according to the FSM.

In my experience, what actually gets more air out is heat cycling the motor rather than just running it. Warm it up fully (until the radiator fans come on), then cool it down as much as you can, and repeat.

Natoe · Post by **Natoe** » Sat Feb 25, 2006 1:07 am

it seems to get a little lower idle every time i run it hot.. gonna go do it again and ill do the heat cycle thing. i also got the wrx fuel pump in there finally

it feels so great (cep the slipping clutch)! now i just need to do the awd swap, i even have everything i need.

thank you so much vrg! as usual you helped save another car from certain death.

Natoe · Post by **Natoe** » Sun Feb 26, 2006 8:06 am

ok well, i fixed the ignition switch diode, and it works now like it should! i think it just wasnt working before because other things were wrong at the time, grounds especially.

the idle is still kinda bouncy, more so when its warm. i get a random check engine light sometimes when i come to a stop, but it idles better when its on, then it goes off when i drive away.

other than that i drove it a lot today and it feels great! thanks again for all the help.

vrg3 · Post by **vrg3** » Sun Feb 26, 2006 8:17 am

Glad you got the power sorted out.

It may take a little time to figure the idle out.

What's the trouble code behind the CEL?

A slightly bouncy idle is sometimes caused by a small vacuum leak.

Natoe · Post by **Natoe** » Mon Feb 27, 2006 3:25 am

well i have checked the vaccum lines extensively and even put clamps on where they arent needed so im not sure.

how can i read the CEL code since its in my impreza? i read about how to read it from the legacy by connecting the black wire.... but i dont know on mine

what would happen if my closed/open ends were switched (im pretty sure they are right, but they opposite compared to my 1.8IAC)? it seems to idle at 750-1000 at cold startup and once its warm it gets to 1500-2000... just a thought.

vrg3 · Post by **vrg3** » Mon Feb 27, 2006 4:11 am

You can try the starting fluid check to look for vacuum leaks. Look around the intake manifold gaskets and stuff.

Hook up a switch between the ECU's "read memory" pin and ground, and one between its "test mode" pin and ground. Then you just hit the switch to set the mode.

It seems possible that if you switch the open and close sides you'd get the behavior you're talking about. Check the continuity against the wiring diagram.

Natoe · Post by **Natoe** » Mon Feb 27, 2006 10:27 am

starting fluid check.. heard of it but dont know, ill try and figure it out. maybe i didnt tighten my TB down good enough... it has an old cruddy gasket on it as well.

read mode is with the car off and test mode is the driving one? im still confused, how can i do the read mode and get the CEL to flash? are you saying i ground it?

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IAC and high idle after swap

IAC and high idle after swap

Re: IAC and high idle after swap