Idle stays @ 2k rpm and yoyo

[SexyRed]

Hello,
I just recently installed a used motor in my nsx. The complete motor has very low miles.

Symptoms: upon start-up the idle stays at 2000 rpm and seconds later the rpm would jump up and down 1500 to 3000 rpm. Even when engine warm symptoms persist.

I pulled the codes:
code 13 = Atmosphere pressure.
code 21= front spool valve - the front spool oil pressure connector is kinda damage .

code 36 = tcfc signal.

Bascically code 13, and 36 per the manual is to replace the TCS module or ECU. I have access to another nsx to swap parts if necessary.

I have pulled the clock fuse, the ALB 2.3 fuse, TCS fuse, and the number 5 under the dash without any change.

Additionally, I have a relay or module that is missing - it is label SHINDENGEN. It is located in the center, between the Main Relay and RECTRACTER Modules. What is this module I am missing?

Any input is appreciated.
Danny

 

[NSX-Racer]

Idle behaviour should have nothing to do with the TCS. I suspect a mis-tuning of the idle valves at the throttly body (had this "sawtooth" or "rollercoaster" effect too and solved it after some research in the service manual). Of course if the ECU is the problem my advice is obsolete.

Otherwise you may also look here .

 

[NSXTech]

Sounds to me like you missed plugging in the EICV under the throttle body.
Its soooo easy to miss. (ask me how I know) Its the small 2p round black conn under the valve on the back side of the t-body. If thats plugged in, it sounds like you have a vac leak somewhere- I would check all vac hose connections again. The baro sensor is inside the ecu, and rarely goes bad. If you did not have this code with the old engine, it is probabally a wiring problem. Code 36 is present because of a suspected hard code (13) which means the TCS CU is in the pending failsafe mode.

Let us know what you find.
HTH,
MB

 

[NSX-Racer]

Sounds to me like you missed plugging in the EICV under the throttle body.

Would be interesting to know if your car is TBW or earlier (model year?). The throttle body and the plug Mark wrote about (isn't it the plug that has to be unplugged when you adjust the idle valves at TBW cars and replug afterwards?) is different on these model versions. AFAIR this plug is not under the throttle body at my '98 car but a bit more higher.

 

[NSXTech]

Its a safe assumption (on my part) that it is not TBW as code 36 for TCS was eliminated in these models. All TBW cars use code/subcode routines like the ALB system for TCS probs. The connector I mention is under the valve, not the t-body. On TBW cars it does not excist at all- it is integral in the throttle motor asy.

MB

 

[NSX-Racer]

Thanks for the info, Mark, I was fooled by your sentence in the previous post:
" the EICV under the throttle body."

 

[NSXTech]

If I had written what I meant to say, then you would have known what I meant was not what I wrote, so you would have had a clearer understanding of what you were supposed to gleam from my post.

:wink:
MB

 

[SexyRed]

Thank you Mark and Nsx-Racer,
I will look up the EICV when I get home. If you know what page it is in manual I would also appreciate that.

Yes, the car is OBDI 1991 manual tranny.

Additionally, I also installed a new "used" used wiring harness. The car did not have this symptoms on the previous motor. Though I did check the check diagnostic code on the previous motor.

Danny Lai

 

[SexyRed]

Mark,

Do you mean the EACV? it is connected. I have recheck all the vacuum lines everything seems intact.

Any better better description in finding the EICV.

Danny Lai

 

[canuck]

Also, be sure the cooling system is thoroughly bled. H/A vehicles will also get the "idle yo-yo" if air pockets are messing up the coolant temperature sensor readings.

HTH

 

[NSXTech]

Mark,

Do you mean the EACV? it is connected. I have recheck all the vacuum lines everything seems intact.

Any better better description in finding the EICV.

Danny Lai

Danny, Yes. Same part. At this point, most likely scenario is a wiring or ecu prob. The baro (PA) sensor is critical to a/f, and therefore idle control. It tells the ecu your altitude, and therefore air density. It is either grounded or open, telling the ecu you are in Death Valley, or in the Himalayas when you are not. Just playing the odds, the used harness you installed is a bit more suspect, though one may have trashed the other (ecu being the 'fuse')

I would suggest doing the tests on pages 11-54 and 11-55 of the SM.
Lacking the pinout tool shown, you can access D5 by backprobing it at the ecu. 'D' is the bottom of 4 connectors on the left side (as you view it) of the ecu. '5' is the third wire down in the row closest to you. It looks like this:

O1 O2
O3 O4
O5 O6
O7 O8
lock[O9 etc​

'lock' being the tab you squeeze to get the connector out.

NOTE to others- this pin arrangement is differant on OBDII cars.


PMme if you have any questions.
HTH,
MB