Thread: Idle Surge / Hunting Idle - 200sx SER with Avenir swap

The idle fluctuation was a temporary fix. It went back at it after I played around with the TPS. Apparently something was set wrong which caused the ECU to think the TPS was ON all the time and it wasn't actually in idle mode.

Im still tearing my hair out over this issue. The RPMs just keep jumping up and down.

I did a smoke test and boost leak test. No leaks.

Anyone in the Chicagoland area want to drive by and help me take a look? I'll pay for your time.

TPS is not the cause it's the effect ... Just fixed this same problem on a buddy's FC .. Let me explain a little bit what's happening because then it'll make some sense. You have too much air "somewhere" going into the motor so it goes high .. The ECU doesn't see TPS sufficient enough to know that you are driving so it tries to preevent the runway rpm because it sees no TPS off of idle there for it over-run fuel cuts ... So check for missing Throttlebody screw. Try clamping off the hose that goes to the idle valve with vice grips maybe the valve is stuck open or not working .. Use carb cleaner to spray around the entire induction system and listen for engine to change tone or speed ..


Sent from my iPhone using Tapatalk

Finally got her running correctly. I'll post pictures and videos in very short order! Thank you everyone for your help. It's great to know that such forums exist where people have an understanding of these cars.

Here's a little walkaround of the car's exterior. You can tell how much I love this car

And of course, another video which includes engine sounds

So what was the problem/fix? Writing that in this thread may help someone else searching with similiar issues. Thanks

Sure. It was a mixture of a few different things. Initially my idle was jumping up and down sporadically. I just took things step by step to achieve the final result that I have now. Boost leak test and smoke leak test were important (had to factor those out as a first order of business. I also used a Nissan Consult cable to monitor values in realtime on my computer. Extremely helpful device.

Then I did the following-

1. Adjust TPS so that it's between .45 and .48 volts
2. ensure throttle body screw is out enough where the throttle cable doesnt stick, but low enough to ensure that the throttle body is closed at idle.
3. Pinch IACV hose to constrict air going into the valve. This brings the idle down to a manageable level. When it's fluctuating and jumpy, it's nearly impossible to get it into base idle/timing mode.
4. Put car into base idle/timing mode and set the timing to 15 degrees
5. reset the TPS
6. unpinch IACV and idle should get back to normal
7. fine tune idle using the idle screw on the IACV

To clear EGR codes, I just plugged in the EGR temp sensor and EGR solenoid. They aren't really doing anything (just dangling really), but they have prevented the CEL from coming on (at least for the time being).