What causes an engine to cut out when stopping?...

Post by **NafemanNathan** » Mon May 11, 2015 1:50 pm

Yep, it has an ATR one fitted, and no, I didn't know. If you'd have asked me I'd have just assumed there was an OBD1/OBD2 difference, not an ATR/Prelude difference. I would have also thought after looking at the wiring in my car and assuming whoever installed it and got it running knew what they were doing, that either IACV could have been used if the wiring was there (Hence the new 3rd wire), as I had no idea either AEM EMS or Hondata couldn't work a 3 wire ATR IACV.

Glad I do now though!

So where will that 3rd wire run if it's of no use?

Strange as well though that my car hasn't always had this cutting out issue... It's only been the past month or so.

Post by **Merlin** » Mon May 11, 2015 1:57 pm

From the 5th gen serivice manual, 2 wire:

The 3rd wire on the ATR must go to the ECU? The IACV only takes signal from the ECU (on the Lude anyway).

On the Prelude Pin 1 is earth and pin 2 goes to to pin 12 of connector A on the ECU.

Post by **NafemanNathan** » Mon May 11, 2015 2:06 pm

Merlin wrote:One thing that confuses me is how your loom has three wires? I am sure that 4th and 5th gen IACV's are the same?

Only just seen this edit Merl.

The loom didn't have 3 wires, the 3rd one (possibly the blue) has been introduced in order to connect up the ATR IACV's 3rd wire. So my question then was where does that blue wire go if the AEM can't use it?

Although Rich does say "it can only properly control a 3 wire IACV", maybe it can work a 3 wire, but just not well for whatever reason. I did unplug the IACV and the car starts exactly the same, but as soon as I was at the bottom of my road and waiting at the traffic lights, it was idling at 2000rpm. As soon as I got to my folks (2-3 minutes later), with the engine still running, I plugged the IACV back in and the idle settled right down instantly, so it is working.

... Just not well if it's causing the car to drop it's revs to 0 when stopping.

Post by **Merlin** » Mon May 11, 2015 2:14 pm

NafemanNathan wrote:Only just seen this edit Merl.

Sorry I know I am bad for that

NafemanNathan wrote:So my question then was where does that blue wire go if the AEM can't use it?

It could still be in the ECU connector but the ECU wont use that functionality. Not all of the ECU connector has pins in it. Maybe whoever did the swap recreated what the ATR's wiring was like and installed it in that pin location on the ECU connector?

If you could get hold of an ATR wiring diagram it would clear it up.

Post by **NafemanNathan** » Mon May 11, 2015 2:20 pm

Yeah, this was what I was going to do. I'll unbury the ECU and hopefully see that blue wire connected where the ATR manual (if I can find one) suggests it should be.

Therealjj91 · Post by **Therealjj91** » Mon May 11, 2015 4:48 pm

I've just read through all this and I had a very similar problem yesterday when we were mapping my car, he managed to map it out in the end and it was something to do with the ecu running on a closed loop so the ecu was constantly trying to think for it self and adjust so then we changed it to open loop and it sorted it straight away.

Shiny · Post by **Shiny** » Mon May 11, 2015 4:54 pm

Nath, i have a CD with an ISO of ATR ESM on. PM me your address and i'll try and remember to burn a copy and post it to you.

Shiny · Post by **Shiny** » Mon May 11, 2015 4:59 pm

Any use? There are other pages beyond my comprehension!

Post by **Lude-dude** » Mon May 11, 2015 4:59 pm

you could probably do with the ATR ecu pinout?

isn't that just obd2 anyway?

Post by **Merlin** » Mon May 11, 2015 5:00 pm

Shiny wrote:Any use? There are other pages beyond my comprehension!

There you go, the 3rd wire is to main relay

I think I might know why (just hypothesising though). The diagram shiny put up says that the IACV is opened when the engine is started to increase revs. Since the ATR does not have an FITV all the idle control (both cold and hot) is done by the IACV.

In the Lude the cold idle is assisted by the FITV.