SR20 idle issues

[frsh2fourty]

Let me start off by saying, I have researched high and low and found plenty of threads describing my same issue, none of which ever get updated and I've tried everything suggested to no avail.

The setup:

Blacktop s13 SR
Stock injectors
Stock MAF
Stock turbo
7psi
FMIC, greddy BOV not recirculated
HKS exhaust with test pipe
Walbro 255 fuel pump
Adjustable FPR


The problem is my SR has idled really high for quite some. So I finally did the following below and now my issue seems worse.

On a cold start the idle will hunt for a few seconds then stabilize at 1600rpm and will stay that way even when it gets up to temp. If I rev it while idling or drive it at all after that it will start hunting/surging and the idle will jump from 1600-2000rpm rhythmically. I can get it to stabilize if I'm in gear and get the clutch just to the engagement point.

The wideband shows a solid 10 until I drive it and it starts surging at which point it does lean out when the idle drops.

I'm also getting code 34 for the knock sensor which wasn't an issue before.


Used the FRSport guide to set timing to 15* before pulling the manifold (Nissan Data Scan confirms its still set correctly)
Pulled intake manifold
Cleaned manifold
Cleaned throttle body
Cleaned IACV
Replaced all coolant hoses aside from the radiator hoses
Replaced all vacuum hoses
Recirculated the coolant lines that normally connect to the throttle body
New thermal intake manifold gasket
New OEM IACV gasket
New OEM throttle body gasket
Ran heater hose lines to heater core instead of having them recirculated behind the block


That was everything that was done to solve the high idle issue initially. The following is what I've done to troubleshoot this new issue

Checked for vacuum leaks spraying all over with brake cleaner
Checked for vacuum leaks by having a buddy blow cigarette smoke through the line that connects the manifold to the brake booster check valve - this did identify a leak that was fixed before I even discovered the surging issue
Checked for vacuum leaks by spraying soapy water all over
Double checked torque on the manifold
Double checked torque on the IACV
Double checked torque on the throttle body
Verified proper voltage for adjustment on TPS
Verified proper ohm reading for coolant temp sensor
Gave voltage to IACV to verify solenoid wasn't jammed up
Cleaned MAF
Replaced knock sensor with both a cheap aftermarket one from Amazon as well as an old one from a friend spare motor that ohm tested within spec (code still comes back but I'm going to double check wiring next time I'm at the shop)
Relearned the idle - initially after reassembly it was idling at around 2000rpm and I got it down to 1600
Flushed and bled coolant (I know its definitely bled because I took it to the track last weekend and it never overheated)


Other things worth noting

My boost gauge reads 20 at idle and jumps up to about 10 as the idle surges. Under boost it holds a solid 7psi.
I have the Nissan Data Scan app on my phone to connect to the consult port and the data display shows the timing getting pulled from 15 to 0 as the idle surges. I can post a screenshot of the other values when I go to the shop tomorrow if someone wants.
When I pinch that vacuum line that connects the intercooler cold pipe to the IACV the idle seems to stabilize but the car never dies
At the drift event the car ran but felt like it was down on power but not by much
It never really sputtered under boost


I may have tried some other things that I might be forgetting. But I'm looking for suggestions on what else I can do.

I'm about to put a feeler out on my local FB group to find someone with a spare MAF and ECU I can try, but if anyone sees this and is in the west Houston area let me know if you have ones I can try.

[zenkicpe]

I dont see injector o-rings and grommets listed...

[frsh2fourty]

I dont see injector o-rings and grommets listed...

The injectors were flow tested/rebuilt by a local company around July or August of last year so the o-rings weren't even on my radar tbh.

I did pull the rail off when I removed the manifold to clean the IACV but didn't pull the injectors from the rail so I suppose the grommets could be shot, though they looked fine on inspection before I reassembled everything and didn't appear to be leaking.

I suppose it wouldn't hurt to go ahead and replace them as I don't think I ever have...but is there a way to definitively identify that as the issue without just replacing them?

[OnTheChip]

This is a common problem with non-recirculated BOVs.

[frsh2fourty]

This is a common problem with non-recirculated BOVs.

People have mentioned that in some of the threads I've found, and I suppose that could be why the idle is high, but it doesn't explain the surging as I've had the swap in the car for something like 4 years with the BOV venting to atmosphere and its never done that. I'm not trying to argue against your suggestion, just trying to better understand the issue.

[Jefro240]

People have mentioned that in some of the threads I've found, and I suppose that could be why the idle is high, but it doesn't explain the surging as I've had the swap in the car for something like 4 years with the BOV venting to atmosphere and its never done that. I'm not trying to argue against your suggestion, just trying to better understand the issue.

The Blitz SS I have on my S13 has been problematic to say the least. Originally when I got it, it wouldn't open. Finally got it working & worked fine for years. Then outta nowhere it intermittently started leaking as it wouldn't seal properly sometimes after opening. Then it got the point it wouldn't seal period. So I had no choice but to re-circulate it.

Don't use Brake Cleaner or a Cigarette... Get a propane torch and turn the gas on. Move it all over the BOV & even stick the end of the torch right into the BOV exit to force propane in & see if the idle changes.

Lack of re-circulation was never an issue for me. Idled fine as long as the damn BOV closed & sealed properly.

[frsh2fourty]

The Blitz SS I have on my S13 has been problematic to say the least. Originally when I got it, it wouldn't open. Finally got it working & worked fine for years. Then outta nowhere it intermittently started leaking as it wouldn't seal properly sometimes after opening. Then it got the point it wouldn't seal period. So I had no choice but to re-circulate it.

Don't use Brake Cleaner or a Cigarette... Get a propane torch and turn the gas on. Move it all over the BOV & even stick the end of the torch right into the BOV exit to force propane in & see if the idle changes.

Lack of re-circulation was never an issue for me. Idled fine as long as the damn BOV closed & sealed properly.

Makes sense, I'll give it a shot.

The BOV did come with the swap and I have no idea how long the PO had it before that so it could just be pretty old. It would be super odd if it just happened to fail completely right after I fixed the other stuff though.

[louisdaboois]

Makes sense, I'll give it a shot.

The BOV did come with the swap and I have no idea how long the PO had it before that so it could just be pretty old. It would be super odd if it just happened to fail completely right after I fixed the other stuff though.

The BOV sounds like it could be the culprit. Mostly likely the internal plunger spring is worn out or gummed up if it is, in fact, the problem.

Skimming through your list, it sounds like you've exhausted all of the potential vacuum leaks. This may be silly, but worth a shot at checking the ignition timing, spark plugs, fuel pump (adding a relay will help stabilize the voltage).

Hope this helps.

[frsh2fourty]

The BOV sounds like it could be the culprit. Mostly likely the internal plunger spring is worn out or gummed up if it is, in fact, the problem.

Skimming through your list, it sounds like you've exhausted all of the potential vacuum leaks. This may be silly, but worth a shot at checking the ignition timing, spark plugs, fuel pump (adding a relay will help stabilize the voltage).

Hope this helps.

I did reset the timing back to factory 15* using the writeup from FRSport before deciding to pull the manifold to clean the IACV, I'll add that in the OP. Nissan Data Scan shows the timing still set at 15* too before it starts hunting.

I did the fuel pump relay around the time I did the swap.

Plugs looked okay before the event this past weekend but I'm sure they are due to be changed after thrashing the car at the drift event this past weekend running as rich as it was.

[frsh2fourty]

So just to update since I finally got a chance to work on the car...

I tried the propane method to test for vacuum leaks including the BOV which didn't seem to show anything.

I finally broke down and bought a new IACV and installed it yesterday. That seemed to fix the surging idle but idle still won't go below 1600 RPM when warm with the idle screw closed completely and wideband gauge reads about 11.0 so its still running pretty rich.

I'm going to make a boost leak tester and try that sometime this week and I'll update again after that.

[mirandaturboFL]

Check your spark plugs and gap them to .032 to .029.

I had a similar issue and the causality was a bad O2 sensor and the wrong plugs gaped incorrectly. I'd try the cheap stuff before you get into changing the more expensive stuff.

[cbeuglas]

Also there is a set screw on the throttle body. It might have moved and holding the throttle plate open. Also check the throttle cable and make sure it is not holding the plate open

Sent from my SAMSUNG-SM-G930A using Tapatalk

[frsh2fourty]

Update time because I hate searching for problems and finding a thread with a similar issue where OP never posts the resolution...

First wanted to say thanks to the guys offering suggestions.

So Martin from RS Enthalpy did a local dyno day in town last week and I decided after testing and replacing everything I could think of it was time to see if a tune would help or at least pinpoint the problem. The tune was something I've been wanting to do for a while but didn't want to give him a broken car and waste both our time.

Prior to the dyno day he told me to send him my ecu so he could install his chip with a base tune. For some reason I got curious when boxing it up and decided to open it just to check things out. It never crossed my mind to do this when trying to track down my idle issue because I assumed if the car started and ran the ecu had to be fine.

Well I came to find out that the ecu already had an m377-1 multi board chip installed. So basically the entire 7 years I've had this swap, its been running on some random tune that the guy I bought it from never told me about. I guess whatever it was tuned for didn't come with the swap but it didn't make enough of a difference to really hinder the cars drivability. With Martins base tune the car idled smooth right around 8-900rpm and we got it tuned on stock fuel pressure, timing, and boost to make around 230hp which is exactly where I wanted the car to be.

tl;dr: rich condition and high idle were due to a random tune I didn't know I had.