I recently swapped the ecu in my 99 GS-R to a Hondata tuned OBD1. Now it surges pretty bad, but only with this ecu. If I swap my original OBD2 back it doesnt surge, though it runs pretty crappy. I've tried everything that has been posted on here about surging, even changing all my gaskets.(TB, Intake,etc...) Any ideas, Maybe a bad tune?

 

Unplug the EVAP solenoid and it will get rid of the surging.

 

you might have a little air in your cooling system... that happened to mine when i swapped it. i took it to the shop and they took the air out of it no problem.

 

I unplugged the EVAP and it didnt make a difference. I've tried bleeding the coolant several times, that didn't seem to help either.

 

Then, the problem exists with the basemap. The IACV duty cycle is set way too high.

 

Kinda what I was thinking. Time to try tuning myself!

 

Well I hooked my laptop up tonight and started going over all the paramaters and it seems that my base idle was set too high. The target idle is set at 950 and the idle screw alone was holding it over 1k. So when the IAC would activate it kept kicking in the fuel cut circuits. I adjusted the screw to bring the idle back down and its all good now.