Another Supercharger Idle problem thread | Starting to get desperate
 

Hey, Seb is doing me a solid and helping me on my idle issue. It is definitely something with the Z, not tuner related.

I believe these issues are all connected, but can't figure it out. I experienced very similar behavior on the on the stock A-W Stillen setup. I am also seeing this on the A-A kit. Pulling my hair out... almost 2 years with these idle issues.

Z never had idle problems before the supercharger install at 50K miles. Has 60K now. I did the install myself. I'm on the mid-experienced level "mechanics" wise. Full lift at home, had multiple projects in the past.

1) On cold start, sits at 900-950 with no issue. When things start to heat up, after some long driving, idle goes above 1,100-1,200 and can't seem to get it down.

2) When I put the clutch down while rolling to a stop, the idle surges between 950-1200. When I finally do stop, it takes a bit to come down.

3) If I free rev, as the revs come down, stops at 1,500-2K and "blurps" (stops, momentary rise, then falls). I feel this is related to above

Attached some VIDS:

High HOT idle:
https://drive.google.com/file/d/1rzc...ew?usp=sharing

Idle Surge while rolling to stop:
https://drive.google.com/file/d/1rs8...ew?usp=sharing

Descending Idle "blurp":
https://drive.google.com/file/d/1tnO...ew?usp=sharing


THINGS DONE SO FAR:

Boost leak done and what was found was addressed. Tried idle relearn but when it's hot, I can't complete because it is high.

Leakdown test ~8%.

Also, I went through some threads and some mention that the A-A kit "Deletes" the PCV. Is the actual PCV fitting replaced with a straight through fitting and then vented to atmosphere? I kept my PCV on but just vented to atmosphere.

Throttle-bodies were replaced with new ones

Supporting mods:


350z HR Nismo (MAF Tuning w/UPREV)
Uprev GT MAFs
A-A kit with 1.5" recirc Tial (on a filter)
Stock clutch/flywheel
Motordyne TDX
Stock Cats
9lb pulley (seeing almost 10psi)
Venting PCV to atmosphere through a mishimoto catch can
ID1050X injectors
Walbro 255 fuel pump(modified in-tank regulator)
Mishimoto T-stat
OEM 370z plugs (1+ step colder for 350zHR, gapped .032)

UPDATE:

Just added a fitting to replace the PCV so it's straight through the mishimoto catch can to atmosphere. Did not help.

When you say you replaced your throttle bodies, which did you replace them with: OEM or EPS? (I believe there was a third option at some point but don't recall 100%)

At first, I bought used ones from a low mileage Z. Then I got new Factory Hitachi throttlebodies. Although, these ones say Hitachi on them, not Nissan. Issue was seen before and after all the replacements.

Also forgot to mention, I made a custom TB cable for the driver's side. Each wire has hi-temp silicone-based sleeve and also individually shielded. They are then grounded. Still did not help. I'm using brand new cables I picked up from TopGunz.

.. tempted to do the same for the MAFs cables, but not really sure. It's a lot of work and I did not see a change when I did the TB

Just checked all hoses for kinks or awkward bends. All my hoses have factory style clamps on them. Didn't see anything out of the ordinary.

Going to use a vaccum smoke tester to pump the exhaust tomorrow and check for leaks.

I also have a brand new factory fuel pump assembly and a new Walbro 255. Going to reinstall and recheck my previous work.

Have you tried to take off the catch cans? Sometimes they can keep pressure in and since you took away the pcv system maybe some how it is getting stuck in there? I know precision turbo suggest to not have one for this reason.

I ran without a catch can initially with the A-A kit. I installed one just to rule this out. In both cases, still saw the weird idle as described.

Hey man,

I've been on this journey with Supercharging my Z since January/February. Stillen supercharger kit with the SOHO Motorsports A2A kit. I am still going through getting the car to a stable state as well. I just found another hose that was cut by the serpentine belt. I digress.

I used to have a very rough idle with an UpRev tune. Even rougher when a vacuum hose popped off unbeknownst to me. Hose was reattached but idle was still very rough. Last week I got re-tuned through EcuTek and it idles stably at around 688-700 rpm.

Just with that, I thought it worth the switch to EcuTek and a different tuner.

I'm still dealing with the engine heat issue. I went from 50/50 stock coolant to Waterless (temps were way too high still), and now in the process to switching to distilled water and water wetter. Then, I found the cut hose.

Good luck, man!

If he's using Seb, the problem is guaranteed not to be his tuner. Also, I'm betting he's already on Ecutek :twocents:

I'm on a 350z HR using Uprev. No MAP sensor so Ecutek wouldn't be worth while.

Have you checked your cats? I ended up replacing the engine because my tune was too rich for the cats and it melted it and sealed it up...

I went and got headers and test pipes to go with the new engine. Worth a shot?

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Oh yeah... duh! :facepalm:

Interesting, I would think that going too lean (increase in heat) would cause the cats to go. I have a lift at home, so i'll put it up this weekend and check the cats. I used to have HFCs and I blew through those. I put stock cats on and has only been 1K miles tops on them with the S.C. Cats have 50K miles on them. I have been planning on using some testpipes and welding on some Cats from a v8 or something.

I just learned that after I'd melted my HFCs. Basically running rich has excess fuel that exits the engine and into the cats causing another detonation/combustion. In this case, it's a lot hotter than the exhaust since the cats are having to deal with direct flame which exceeds it's heat tolerance and causes it to fail.

When HFCs failed, it sealed up and blew back debris into the engine. Hopefully, this isn't the case with you.

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