EJ20G ECU with IAC issues

[farfrumwork]

Cool. My Rob chipped ECU is working... except for the IAC control.

Am I the only one to install the Rob chipped ECU and converter to a EJ22T longblock (with stock heads/sensors)? It seems like most reports are from EJ22T/DOHC combo's.
Any other issues out there with the IAC control?

Basically it acts like the IAC is reacting absolutely backwards. It won't idle well (very low, fighting to stay alive) cold OR hot, and can feel like a vac leak under normal driving. I get an immediate and constant Code 24 (IAC), which I never had previous to the EJ20 ECU install.

I've been looking through all the IAC and EJ20 posts here and have found some mention of switching the IAC leads when using the EJ20 ECU with the EJ22T engine/sensors. I may bullet the leads by the connector bank at the battery and see if switching them works...

Thoughts?
-Chad

[wtdash]

I initially ran the EJ20G ECU on my stock EJ22T. No issues w/the IAC....Mine idled better w/the EJ20 ECU.

Also, FWIW, I have an extra unchipped Z4 EJ20G ECU and it worked fine, too.

TD

[farfrumwork]

damn, well that kills that theory... maybe. Yours is a '90 right? I think there were a few different IAC's used throughout the years. The EJ20 could play nicer with earlier IAC's (?)m than with my '93.


I did use different sources for +12v and GND. But still a switched +12v, and nearby ground. I don't see how this would affect only the IAC operations without affecting the main output of the converter (ignition control, which seems right on).

thanks!

[wtdash]

^ My IAC should be from my '93 SS donor....but I'm not going to guarantee it...I've swapped a lot of stuff on my car over the last few years. But it's definitely an EJ22T IAC, and not from the original '90 EJ22e.

[Legacy777]

All the ej22t motors used the same IAC valve. Only the 90-91 MT non-turbo's got the two wire IAC valve instead of the three wire.


Chad,

Can you elaborate what you did for the +12v and ground? Where are you tieing into for the switched 12v and ground leads? The 12v switched isn't as big a deal IMO, but depending on where you get your power, it could be lower voltage if the wiring isn't as good.

For the grounding however, it's much more critical IMO. The stock ECU grounds itself to the intake manifold. There is a ring terminal on the back side of the manifold on the driver's side. I would recommend grounding the ECU to this spot, and then adding a ground lead from there to the negative side of the battery. This will help eliminate any variation in ground voltage differences. Give that a shot and let us know how it runs.

[farfrumwork]

Hey Josh,

I only thought of the wiring as I've found mention from a couple others about having to swap the "close" and "open" leads for the IAC (something about different wiring, not different IAC's, between years...) Haven't gotten to this though as it seems less than likely.


Anyhow - power/ground for the converter: I pulled the switched 12v from what I think is one of the main ignition wires (I have an Alpine alarm that uses this as well), and I grounded to the steering collumn (where other accessory grounds are located). I would think that the power/ground for the converter would only affect the ignition operations, but electrons have conspired against my natural thought process in the past... the ECU is powered/grounded just as stock.


I will reiterate that I had ZERO issues with the IAC (or anything else for that matter) prior the install. I have now double and triple checked all of my work and other related sensors - everything is solid.

It appears that the IAC is still operational (not stuck), as I can alter the idle rpm through the allowable adjustment of the IAC solenoid, and it will revert to the preset default (~1200rpm) when I unplug the IAC. With the IAC plugged in, and adjusted to idle at >1000rpm, it will not respond to load increases like it should; I hit the DEF button or step on the brakes and it drops idle - not increases. I think that either the ECU is not controlling the solenoid properly or the ECU is trying to drive the IAC backwards ("open" "close" wiring).
All is fine when off idle when the IAC is no longer involved.

I will tie my convertor ground into F47 #14 tonight and see if that helps.

Thanks for the input - this has been driving me nuts! (I hate issues I can't resolve - you have no idea how much time I have spent searching IAC issues and general operational details of PWM solenoids... oy)


-Chad

[Legacy777]

Yeah, I'd try swapping the open & close pins to double check.

Regarding the wiring. If it's on the igntion converter, yeah I agree, it's probably not as big an issue. I would also suggest adding an additional ground lead from the negative terminal of the battery to the intake manifold ground. It can only help.

Let us know what you find out.

[farfrumwork]

Well, I moved the converter ground to F47 #14. I had the F47 plug out so why not.

I also swapped the F47 #1 & #2 (IAC open & closed). Now you would think that this would either fix my issues or make them worse (and more than likely the later). I wouldn't say it's better - but it did idle a higher than before, ~1300rpm vs ~500-750 (same, stock IAC solenoid position) but is still throwing a code #24 (IAC) and running a 2-3second oscillation of 250rpm. if that makes any sense. And it is still not reacting at all to any load application.

It looks like the ECU is not driving the solenoid. Is that a valid conclusion?



oh yeah, I have extra grounds run from the batt to the pass head, alt area, and rear engine bay wall. This has been installed for years...

[Legacy777]

Yeah it sounds like something is up with your ECU.

[Legacy777]

Chad, split your topic from the original thread.

[farfrumwork]

That's cool.

I am going to try to "unchip" the ECU per Rob's input and see if the tune has something to do with this (or at least eliminate some variables).

I'll get there!


*on a side note, I will have a new (or another) car starting tomorrow... let's just say I'm still in the Legacy family but my new ride has me buzzing - like a Bee or something.

[farfrumwork]

OK - FIXED!!


After trouble shooting remotely with Rob, we determined the ECU must be hosed. I sent it back to Rob, and he confirmed (ECU is bad.. in a weird way, but bad nonetheless).

I have a new 'chipped' ECU in the car now and all is well
Hopefully I can dyno it soon too.

-Chad

[Legacy777]

Good deal. Glad to hear you finally figured it out.