Fluctuating Idle?
 

Car runs perfect but tends to surge between 750~650rpms. The idle is set to 750rpm tuned on Uprev. Doesn't give me too much of a problem driving and no check engine light. Maybe I'm overlooking something. The last thing I touched was the intake. Besides that nothing has changed and the problem ONLY persist when the car is warmed up.

Couple things that I haven't tried:
1.Clean MAF sensor/Throttle body

2.Oil change and cleaning out VTC sensors and changing gaskets.
(Maintenance things)

3.Check for vacuum leaks. Not sure if this will randomly pop up but will try.

4.New coils? Spark plugs are fairly new (500 miles~)

Just out of ideas and like I said the car runs fine with no issues. Not sure if it's a misfire or something of the sort but certainly seems like one. Anyone ever have a similar issue and what worked out for you? I'm a busy guy working through the week but for now I'll just like some things maybe I can check until the weekend on my spare time.

DO NOT TRY AND CLEAN THE TB, OR MAF!

If you screw those up they are literally trash and hardly ever do they actually need a cleaning. Do a TB reset by doing the pedal dance and or unplug the battery for like a couple hours.

Do a vac test first, check the tune make sure it's tuned properly. Then check coils and plugs.

Maybe even injectors maybe one is going bad. He'll make sure injectors are seated properly. Common spot for vac leak is injectors when people remove them and don't seat them properly.

------ UPDATE --------------

Found a major leak on my Y pipe. The flex pipe was torn and letting out a pretty bad amount of air. Put a dollar just to see it flap around like jello....

Now my question is, will this cause a misfire/ rough idle? It IS near the O2 sensor and have read that this can cause the same problems that I'm experiencing. I'm pretty certain this is the problem. Has anyone ever had a similar issue?

Just ordered a new Y pipe (Motordyne XYZ) since it was leaking anyways.

Thanks for the help. I've just tried looking for vacuum leaks. Sprayed around the plenum and throttle body. Tried various ways as well to get spots that may have seemed to leak and no luck. As for the injectors they haven't been touched at all since I've gotten the car. The closest I've been to touching them were replace leaking valve covers. This was about 6+ months ago. I won't rule this out but if a new Y pipe doesn't fix the issue this is probably my next to check area.

I've also tried mixed variations of moving the coils around and also had a Z buddy to borrow a for sure working coil to swap around cylinders.

If it's near the sensors I'd say yes. You're allowing excess air to contact the sensors throwing off its calculations and adjustments. Wouldn't think it would throw a misfire but it sure doesn't help.

Exhaust leaks can cause weird problems. One of my exhaust gaskets between my Y pipe and Bank 2 Cat blew out 6 weeks ago. I could easily tell something was wrong before the CEL came on as the leak was easily heard when driving at low speeds (really annoying in parking garage at work). This is just a few inches difference from the leak location you're describing. Both are downstream of the O2 sensors and I still had a CEL pop because of the O2 sensor in the Bank 2 cat. I didn't experience rough idle problems, but I could tell the engine wasn't running at it's best. Power output seemed slightly down, fuel economy was also affected. In the end, I decided to slap on R-Pipes and got a re-tune done.

Note: Crappy O'Reilly Gasket. I was in a pinch after doing my clutch (requires dropping exhaust system from cats back in my case), and forgot to order some good quality ones online prior to starting the job, so I hoped for the best with those Oreilly gaskets. Even with high-temp gasket maker, it still blew out, but lasted almost a year. Using the Z1 gaskets now, much better fit and seem much higher quality.

Yeah mines isn't necessarily a leak it's almost a hole lol. I know this is bad and to be honest I had always thought it was normal after test pipe installs for the DE to have a "hiss" on deceleration and revs. Over time I'm guessing my flex pipe stretched open bigger. Now it's a prominent leak (hole about the size of a dime) and upon checking again just for any other leaks I have I discovered the driver side is leaking as well. Not nearly as bad as the passenger side. I believe this is still the issue only because metal expands and letting out more air with the leak which explains why this only happens when the car is in full operating temperatures (190F - 200F~). AGAIN I will update after the Y pipe arrives and installed.

Fuel injectors seem to be all firing and in all orderly condition. DID NOT take off my plenum to inspect them yet but I did have a yard long screwdriver and fiddled my way around to listening to each injectors and they're all firing. This doesn't eliminate one of them leaking or clogged though. Also to mention I do ONLY pump 91oct and only that since getting the car 3 years ago. I doubt fuel would be clogged.

I pretty confident this isn't a vacuum leak. Correct me if I'm wrong but if a vacuum leak is present shouldn't the revs be higher or fluctuate above my set rpms (750rpms)? Tried another bottle of carb cleaner to go around and got fancy to spray around the lower plenum as well and no luck.

-------------------------UPDATE--------------------------

Y Pipe is changed and still having the issue. Kinda scratching my head on this one now...honestly can't think of anything now either but I guess I'll be looking at injectors next weekend...anything else someone could think of for me to check?

Tried flashing my previous tune before the current one just to make sure and still having issues. Just kinda stumped now.

STILL NO CEL!

-------------------------------FIXED----------------------------------------


Heat shield on intake had a open pocket so when the cooling fans kicked on it blew hot air towards the intake and disrupting air flow. Adjusted my heat shield and VIOLA! Worked like a charm. So if anyone is having a idle issue then...be sure to check your heat shield! Sometimes it's the simplest things that will cause you headaches.

(I should mention I am running the LMT 4inch intake as well in case anyone else runs into this issue.)

I have the same thing and I can tell you what I have done over the last few thousand miles which made no difference to the idle (to fix other issues, but I've noticed the idle fluctuations are still present). Replaced MAF sensor, cleaned the throttle body, disconnected the battery overnight to reset the ECU, replaced spark plugs, replaced ignition coils, replaced fuel injectors, replaced fuel pump, and replaced fuel damper. I recently replaced my alternator as it had 170,000 miles on it and was only putting out 13.9V and that made it much better...but it is still there.

Throttle bodies
 

If any of you guys are interested I have two practically brand new OEM Hitachi throttle bodies for sale! Let me know