'00 civic hatch, with swapped b16a2, garrett t3/t4, obd2b to obd1 harness, p28 & hondata: turbo's installed and working well when the car's warmed up, but after cold start, if you blip the throttle, the idle starts loping up and down about 400 rpm. it's tuned with Hondata s200b and the idle valve is fine, idle was great before the turbo/hondata was installed, and it goes away after a minute if you start driving.
Also, there's a popping from the exhaust, sounds like misfires, when at hot idle but the A/F is fine the whole time.

any ideas?

 

i have the same problem with my n/a setup, check all the hoses and connections on the i/m, make sure they havn't come loose.

 

no, they're all fine, I installed it myself and checked it numerous times after having the IM off, and it only happens on cold starts, if it was vac, it would happen all the time

 

then ur idle valve is not fine... its on its way out. get used to it or change it. after it take a full on dump it'll be perminant til u change it..

 

why would the idle valve be no good all of a sudden? within 12 hours of sitting. Could it have something to do with the hondata tune, I believe there is an IAC setting when tuning hondata?

 

it's the pcs valve that sits on the fuel rail and has a hose going in to the charcoal canister, and one hose going to the intake manifold, unplug the connector on the sensor and see what happens, should help a lot.j it's an obd2 to obd1 thing because obd1 doesn't have that, so the obd1 ecu doesn't control it properly and it lets too much air in to the intake manifold causing the idle to fluctuate.

 

Thanks Projekteg, I was hoping you'd see this post, I'll give that a shot, much appreciated.

 

SUCCESS!!! you're the man projekteg, you've saved me a lot of headaches and a few bucks I'm sure. I assume that will change the tune now though, is this so?

 

no, it won't affect the tune, it's just some emissions bull ---- to pull the extra gas tank fumes in to the intake manifold so they don't go in to the atmosphere. unplug the hose on it that goes to the charcoal canister also so the gas tank can still vent.

 

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