Specifics of Idle control on EJ25 with AT

[Ross]

I've just done a manual conversion on my '95 (JDM) legacy, EJ25D. I have it running with no codes etc, and all is generally well.

 

Now I have to fix some rough edges. First is the idle control..... Since it is an automatic ECU (manual EJ25s of this vintage are very rare over here, so I wont be doing an ECU swap) it likes to idle quite high to start with, but the computer does seem to be learning slowly how to fix this -- it now idles at ~1200, down from ~2000 when I first started it.

 

I suspect that, as it is at the moment, the computer will never have good control over the idle, since it doesn't know if it is in gear or not. It is wired as per most previous manual conversions I have found -- tricked into thinking it is in neutral constantly.

 

So, my main question is, will the ECU recognise that the VSS indicates that the car is moving and therefore not adjust the idle? Or will it try to adjust the idle when coasting in gear (throttle closed, in gear but ECU thinks is in neutral). This would obviously cause confusion.

 

A secondary question, does the ECU adjust the idle when in 'Drive' separately (or at all), or does it only adjust when in neutral or park?

 

Cheers.

[Fairtax4me]

There is a pin on the ECU that has to be grounded (on US models anyway) that tells the ECU whether to control for manual or automatic trans. Not sure if the pinouts are the same between the US and NZ models, but try searching the forum here and you might find which pin it is.

[Ross]

Yes that is on my list of things to do.

 

It's throwing a code 31 (TPS) now, I'm guessing that's because it's seeing the engine doing 3000+rpm with the throttle shut when in 'neutral'....

[Gloyale]

Trick it to think it's in Park, not neutral.

 

It keeps the idle high in neutral, espescially during and after coasting cause it thinks you are "between" shifts. So it keeps the idle up a hair for better synchro action.

 

unhook the wire you grounded for Nuetral, and ground the one for Park instead.

 

 

 

 

Either that, or better yet, cut the AT id wire so the ECU thinks it a Manual, and then hook up the Neutral switch in the trans. In this case do not ground either neut. or Park.

 

 

I don't think the TPS code is related.....check/fix the TPS adjustment first before messing more with Idle.

[Fairtax4me]

Might also double check the adjustment of the throttle and cruise cables. Just for kicks.

[Ross]

I need to keep the tranmission control computer in the loop for the moment to keep ABS going.... although I do have an idea how to get rid of it, I'll save that for another day. I'm presuming cutting the AT ID wire etc. to tell the ecu it's a manual will mess with this.

 

The reason I think the TPS code is related to the manual is that it is the only thing that's changed. It doesn't bring up the check engine light, just stores a code. I wouldn't be that surprised if the ECU was a bit confused about how the engine is reving so high in neutral with the throttle closed. May as well sort the gearbox issues before I start messing with it anyway.

 

We have fairly strict warrant of fitness standards here, and technically the car should get a low volume cert since it has been converted to manual, but if I get it looking and running nicely it wont be noticed -- so I do need to get this idle etc. sorted anyway.

 

So -- I might try the park instead of neutral suggestion first and see how that goes...... But I suspect I'll need to get the ABS working without the trans computer so I can get that out of the way.....

 

Cheers guys.

[Ross]

Has anyone actually heard of a conversion where the TCU has been removed, the ECU wired to know that it is now a manual, and the ABS tricked into working?

 

I've read plenty of talk about it on various forums, but never a verified case of it actually working in the end.

 

From what I've read, I'd need to:

--Ground the AT/MT ID pin on the ECU

--Remove TCU

--Ground the wire going from the TCU to ABS unit

--Atach the neutral switch to the appropriate ECU pin

 

Sounds perfectly reasonable that this would work, but it would be nice to actaully hear that it has been verified...