Stuck at Higher Idle/Idle Surge

[ChillyWilly3]

I have a 1996 Nissan SE with an Nsport Stage I turbo. I didn't post this in the Turbo KA section because I think other than checking for loss of pressure in the I/C, this idle problem sounds like something common (or so I think).

I was driving one day and decided to push the turbo for the first time. I shifted from 2nd to 3rd gear, but because I'm a putz, I missed 4th and revved the car to 4500-5000 rpms when I hit the accelerator. I eased off and downshifted and decided that it was time to end my little experiment and just go home. Well, I noticed while cruising slowly to my neighborhood that at neutral (it was downhill), my idle was stuck at 2300-2500rpm. It stayed that way even after keeping the car off for 5-10 mins.

After 30 mins, the idle then showed 1100-1200rpm. I test drove the car and notice that after letting off the accelerator (getting ready to stop), the idle will surge from 1100 rpm to 1500 rpm every time. The car is currently at this state.

The IACV is brand new and the EGR section was removed and blocked-off. Normal idle was tested before and after turbo install and it showed 750-800 rpms as expected. I initially thought the TB butterfly was getting stuck because of the erratic change in the idle. However, I had cleaned and carefully blocked off the TB throughout my turbo install. It's still a suspect until I clean it again of course.

I did a search and came out with these things I can do to troubleshoot my problem:

- Clean TB connectors- Clean TB (Butterfly getting stuck?)- Disconnect/reconnect battery (Reset ECU?)- Install my A/F Gauge (Running rich?)- Check for vacuum leaks (I/C piping and vacuum hoses)

I can just change the idle via the idle control on the intake manifold but that's my last resort (I need to know what caused this).

You're input is appreciated...

[bj180sx]

have you tried adjusting the idle. Also I would definately check for vacuum leaks. Might also check accelrator linkage and claen any debris on it.

[ChillyWilly3]

Thanks. I will check for vacuum leaks this week and tighten all hose and piping connections as well as the accelerator linkage. Changing the idle via the valve is my last solution. If the idle got changed somehow, I need to know what caused the change.

One question though about leaks, I have a boost gauge that shows the vacuum as well as pressure readings from the intake mainfold side. It shows a solid 20 inHg vacuum even after the incident. If there was a leak wouldn't it affect the pressure/vacuum and I should see this reading change? Just wondering...

Also, I started hearing my alternator whine now. I have no significant load on the electrical system (stereo system is bone stock, etc.). I'm not sure if my alternator is about to go bad or not, but I read that if the alternator is not charging adequately, the voltage regulator informs the ECU to bump up the idle. Could this also be a possible culprit? I'll go to Autozone and have them check my alternator anyway to see if it's charging correctly.