Stuck at High 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)
- FMU (RRFPR)

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...:)

[silvia240]

did you notice any temp changes? i.e. temp is high or low?

[ChillyWilly3]

The temperature gauge reading was stable during this whole affair, and it was showing what I normally expect when the engine has reached optimal operating temperature.

I think I might know where you're going with this. I thought about whether the electric fan turning on caused the idle to rev higher, but the outside temperature that week was on the cold side. Even if it did turn on, it should have stayed on for only a certain amount of time (until it reaches a certain temp) then shut off, so that the idle goes back to 750-900 rpm range. But it didn't.

Well, this week it has gone back to its normal idle rpm of 800. Not sure what happened. :confused: This might be a clue for somebody out there.

Anyway, thanks for the advise. I'll do some more research.