Rough Idle
 

I just got a 2013 Scion FR-S (have absolutely fallen in love with the car). I bought it second hand and the only thing that was ever done was it was given a Flex Fuel tune from delicious tuning. Now to my problem, or potential issue. I have heard the early FR-S was prone to rough idle and “rev hunting” at idle. I found that the issue was fixed with an ECU reflash. My engine still idles rough, it has a slight spike in RPMS every now and then when the fan is running. Shouldn’t the tune have fixed this issue? Or is the RPM spike a normal occurrence?


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Mine is 2014 MY15 and has a rough idle when cold.....fine when warm.

Tune and update are different.

I can apparently go to any Toyota dealership and have them reflash it for free. Think that’d be a good idea?


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If it already has a FF tune on it then that's likely a step backwards. Heck, they might not even be able to flash it at the dealer anyway. I'd get in contact with Delicious, and see if they could fine tune it.

I've heard some of these cars just don't like to idle well even with a tune.....just to make sure you're operating with fresh equipment...do you have decent spark plugs and air filter? Given it's a 13 it might be higher mileage..

Dealer wont be able to flash your ecu. Try cleaning the throttle body. Otherwise make sure intake hose clamps are snug. After that, dont worry about it.

Can you elaborate more on your issue? Does it idle rough all the time? Only when cold/only when at operating temp? Same with the rev hunting? Is the swing in revs a couple hundred rpm? is it 500 rpm swing? Are there any other mods on the car? Being it is tuned I would assume there are. Do you know what it was tuned for?

The more info you can provide the more likely and quickly we are to come up with a potential solution before we devolve into trolling.

If the A/C or Defrost setting is on, it's completely normal.
The pump clutching in and out puts an extra load on the engine periodically.

See this is the first boxer engine I’ve owned so I’m not entirely familiar with what’s normal about them yet, the “rough idle” I’m seeing may be something completely normal. I do have crickets coming from the high pressure water pump, I know that’s normal and there’s no real solution. As for the rev hunting, it occurs at all temperatures, but only when the fan is on, A/C or heat. If the fan is off while idling it will not happen.


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It only had 40k miles on it. All cylinders seem to be firing well, the rev hunting really only occurs when I have the fan on at idle (doesn’t matter if it’s a/c or heat). I hate doing oil changes so I get them done at a shop, they deemed the air filter in good condition (I’ve been going there for years and they do know what they’re talking about).


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Unless it's really dramatically swinging around on you this sounds pretty normal to me. If it's really concerning you your best bet would be to post a video of it acting up in here for better opinions.

I’ll do that when I get a chance. It’s not very dramatic, like we’re talking 200rpms maybe.


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Completely normal.

Thank you, like I said this is the first boxer engine I’ve personally owned so I don’t know all the “quirks” and fine details of them yet. This has definitely eased my stress on the issue and I can get back to enjoying my car.


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if it bounces a little bit at a stop light I think that is pretty normal. One way to test it is to put the car in sport mode and drive fast while full throttle and then suddenly slam on the brakes very hard. If you have an idle issue, you will likely notice it here. I believe that is where the idle complaints came from because I think some cars actually were stalling. If you are on the gas and then suddenly get on the brakes, the car should not stall or anything although im sure you will notice the idle still trying to "find itself" a bit but it shouldn't be bad enough that the car lurches, etc.