I am gonna try and explain this the best I can. I have a 99 accord with a v6. The motor was a distributor motor. The motor I put in is a coil pack engine from I think a 00 accord. I swapped the ecu and harness as well. Had a few problems as far as the immobilizer because the wire for the immobilizer was in a different spot on the plug from the 99 to the newer engines.

The issue I am having now is the surging idle. I have been over every cause of the surging idle. The tps sensor, the iacv, coolant and many others. So I pulled up the wiring for the ecu again and found that I do not have a wire in the plug for the tps output signal. Its in connector A which is the one from inside the car. The only harness I didnt change.
In the #31 spot on the 01-02 models is a yel/grn wire for the -throttle position sensor output signal-. The ecu I have is from a 02.
I hope I have explained it the best I can. The only thing I can think of is that I am going to have to use an ecu from a 00. Does anyone else have a thought?

 

The surging idle issue is probably due to something else other than ECU pin A31.

Pins A13, A22, and A31 are applicable to the 01 for the ABS/TCS, which a 99 didn't have. See post #17.

https://www.hondaaccordforum.com/for...p-56150/page2/

 

I have been over everything else I can think of. Pretty much everything that has been posted that can cause it. I have even pulled the whole intake manifold and re did everything down there. Gaskets, hoses, elbows. All just to make sure there wasnt a vaccuum leak I couldnt get too

 

The picture you provided me of connector A shows that the wire in the 31 spot is blue/red. The one that my honda mechanice friend brought me from the American Honda Motor co website shows the #31 spot is a yellow/green wire. But either way they both are coded as (THLOUT) which stands for (throttle position sensor output signal.) And its description is (sends TP sensor signal.)

I am using the motor and harness from a 2000 I believe. But the ecu is from a 2002. And the connector A plug is still the factory 99. The #31 spot only shows its for 01-02. So I am thinking if I get the ecu from a 2000 I should be good. But honestly I have spent so much money replacing all this other stuff thinking it would fix the surging idle. I am trying to get some opinions before I shell out more money for another ecu

 

My sources are also from American Honda's site. You're correct that THLOUT stands for throttle position sensor output; however, that signal from the PCM is going to the throttle position input for the ABS/TCS Control Unit, which the 99 Accord doesn't have. TCS is Traction Control System.

 

But if I am using an ecu that does have that could this be affecting that? I went looking because I had an extra ecu and it turns out the ecu I have is from a 2000. So I may try it just to see. We had the vin number from the other ecu but I do not have it for this one. Do I have to use the vin number from the ecu to code the key to the car?