idle issues please help!

[tomcat5157]

ok so heres the deal. my car ran great until i put a new turbo on then it started doing some weird things. for instance upon start up it runs perfet idles right about 950 where its set. but when i drive it it surges up to 2000 and falls back to 1500 continuosly until i tap the throttle where it will sit at 1500 rpms. now the only thing ive done recently is the new turbo. its a tdo6h 20g turbo with external wastegate setup. now once i put the turbo on it ran fine at first with out a front 02 sensor. (couldnt get the old one out of the old o2 housing) so the next day i put the new o2 sensor in and now i have the idle issue. any feedback would be extremely helpful.
also it throws a 0505 code throttle curcuit malfunction.

 

[Nitrobasher]

Have you checked for boost leaks? The first question you should ask yourself with any driveability issues is "are they any boost leaks?"

 

[92AWDHX40]

http://www.dsmtuners.com/forums/articles-engine-fuel/191137-how-fix-your-idle-surge-problem.html



start here.

 

[tomcat5157]

ok so quick update there are no boost leaks tested it my self when i put the turbo on and again today. did notice something weird today though. when the car is in open loop mode ie front o2 locked out the car runs perfect idles perfect everything. now when its idling "weird" and i unplug the front o2 nothing happens. now i might be wrong but without an o2 sensor input isnt the car supposed to revert back to stoich? another weird thing front o2 volts on dsm link says either .20 or .80 no in between. thanks for the link i will take a look at it.

 

[CleverDSMusername]

could also be the Idle Air Control is going bad, my 1g n/t bounces around 1300-1800 at random and i recently had a customer come in for an inspection with a b18 swapped crx that had a bad IAC and it idled around 1500-2000 (bouncing around in that range)

 

[talontorque]

your p0505 code has to do with the iac motor. It probably went bad. So i would check there first

 

[dudeX]

I had a problem similar to this and it turned out to be the FIAV. I went ahead and deleted it with a block off plate I made from 1/8" sheet metal and it solved my issues. Apparently my isc could not adjust itself far enough to compensate for the additional air the FIAV was letting through. Before I would get the idle fluctuation from 1k to 1.5k until it warmed up but it would still fluctuate from 800 to 1000. After the delete it idles perfectly. Check out FIAV delete and I bet your issues will sound very similar. Hope that helps.

 

[tomcat5157]

ok sorry its been so long ive been out of town... nature of the job. thanks for the input I will be trying the fiav block off tomorrow. as well as replacing the iac. will let you guys know what I find out.

ok so I ruled out the fiav. any one have any idea how to test my iac motor? without replacing it.