Jonathan Doe

2001 CRV AWD auto, just did JDM swap due to slipping trans. Re-Used stock USDM intake and exhaust per the importers recommendation. Did CFK bypass. Now truck will only start and idle when cold.

I have cleaned and or replaced (swapped JDM and USDM sensors multiple times) the fast idle thermo valve, IAC and set the ignition timing and the thing will still not idle worth a crap. ***I have determined the IAC is WORKING but the ECU isn't using it.*** I can MANUALLY open it and get a smooth idle (9 volt battery and jumper harness i made). When following the Service Manual instructions to set the idle speed, once I unplug the IAC and Purge solenoid, nothing changes.

No SES light, TPS is working and reporting 10.2% at idle, perfect.

Thermovalve works like its supposed to so once the car warms up and it closes, car idles like crap. Will not hot re-start unless you feather the throttle. A/C compressor shuts off unless you add RPMs by the throttle. It runs great otherwise and drives fine minus the super low idle.

Did the ECM take a crap in the middle of my swap?? What else could cause the ECM to ignore/not command the IAC to open???

Any Vegas peeps willing to loan me a known good ECM? I really doubt this is the issue but the Service Manual flow charts are tapped out and nothing has worked. I have to use throttle cable tension to raise the idle high enough for the A/C to work, otherwise idle is 650 rpms at BEST (570 ish on average) even with idle screw falling out loose.

OneBadTurboCRV

Sorry, I don't frequent the Miscellaneous section...

TPS should not read that at idle. It should read 0% preferably.

Have you used a DMM and verified voltage feeding sensors? How about continuity / resistance from IACV plug to ECU? Bad wires happen...

Did you unplug your IACV and try setting the idle the correct way? I understand that you have "tried everything", but if you can't get it to idle above 650 RPM you have to figure that out first. Have you sprayed the whole intake down with carb cleaner (or the likes) to check for vacuum leaks? A massive one can cause issues.

You must understand that the IACV isn't needed for the vehicle to idle and is proven when you set idle by unplugging it. If you plugged in sensors wrong accidentally, it could have shorted something in the ECU. You need to start isolating parts from the ECU.

Which reminds me - Did you set valve lash and verify mechanical as well as electrical timing?

Jonathan Doe

The service manual says 10% idle and 90% WFO is the optimum? The TPS isn't adjustable anyways? The JDM one is but it was damaged so I can't use it.

Ran out of time last night to run down the wiring, but the car idled "ok" (not the greatest but good enough) on the USDM long block. We will still test the wires in the next day or so.

We did the "by the book" method for setting the air screw and the timing. Both are in spec but the ECM still won't command the IAC. A vacuum leak would cause the motor to rev, not low idle. I had a hot surging issue that I fixed due to a vacuum leak in the fast idle thermo valve o-ring.

When we unplug the IAC during the idle setting it sometimes*** sets the SES light for IAC open circuit so I know the sensors are correct. If you use the OEM zip tie mount locations it eliminates that possibility. I was very careful when removing the USDM to not break any of the zip ties and I remounted all of them. The power steering sensor is also near by and could be swapped but I'm sure it isn't due to the above mentioned SES light code. When you unplug it it sets a power steering sensor light. Same as the TPS.

Did not adjust the valves as the valve train is quiet and the motor runs very well all the way up to red line. We shorted the SCS connector and set the timing to the "red" mark per the manual. Did nothing to help the low idle.

Jonathan Doe

Bad ECM! FML!

lunar_rd1

Did you short it out or what?

Jonathan Doe

I don't see how, we only did a motor/trans swap.

The other day the A/C stopped working. It appears to be the ECM as well since I can jump the compressor clutch and it blows nice and cold like it should. I found a couple burned resistors:





I did find a local yard with an 01 so I pulled the ECM figuring that the idle and A/C would be instantly fixed, but it did NOTHING! Im really at a total LOSS...

OneBadTurboCRV

Sorry, I kinda had forgotten about this thread. Well, I don't know anything about the OBD-2 ECU circuitry so I can't help there. If I were you, I would make a thread in the Engine Management / Tuning sub-forum with the picture of the burnt resistors and an overview shot of the top of the whole board. There are some very knowledgeable people that repair ECUs for a living that may be able to tell you what burnt to get you headed in the right direction. Up to you

At this point I think you need to take a DMM and start probing and checking voltages and resistance from plugs to ECU. Something is either plugged in / hooked up wrong (I know, you say it's not) or being back fed somehow. Did you ever try swapping back to the stock injectors? Check the ELD? ALTC working correctly?

Just throwing out ideas here, but there has to be something that's being missed.

Jonathan Doe

Will do, thanks!

We checked by unplugging all the sensors with in "reach" of the IAC and each one sets the correct code. TPS sets a TPS code when unplugged, as does the power steering line pressure sensor.

Yup, no change, if anything it ran smoother on the JDM injectors, but oh well not changing them back in again.

I have no idea how to check it, but how does it effect IAC?

The WUT?

Only thing that hasn't been changed is the wiring harness and I get 11.5 ish volts at the IAC plug as well as an electrical load related RPM drop when plugging it back in...

OneBadTurboCRV

You are focusing on the IACV too much. ELD controls things like idle depending on electrical load, this would be something worth checking. ALTC input is Alternator Control and also controls things that can affect idle. Like I said, I would be checking everything at this point, there is obviously a short or problem somewhere to be burning up the ECU and causing things not to work.

Unfortunately I am not there to see what's going on first hand, too many times have I seen people "doing it right" only later to find out they have been doing it wrong all along. Either way, finding out what burned up first would be in your best interest IMO.

tony_2018

there has to be a cel light.....if the tps was off, or something was right ( even transmission) there is a cel for it.