Engine has a natural high idle...?
 

I picked up a 13' FR-S in July of 19' and have been driving it without any real issues for the last six months - I know the engine is roughly supposed to idle @ 650 +/-(10) RPM and the compressor/fans kick on and bring it up to 800 occasionally. Ever since my purchase, the engine has always had a steady idle of 975 +/-(10) RPM and if compressors come on, it goes to roughly 1050.

I guess my real question is what would the normal weakpoint areas be on the FA20 as far as vacuum leaks go, what I should double check besides clamps/intake tubing/torqued intake mani bolts - vehicle has 102,600 miles. Regular service history through a local dealer. It at one point stated it had an aftermarket ECU in it's Carfax Report so I'm curious to see if there's away I can tell if the ECU is flashed too, maybe causing that....?

It was probably turbo before.

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So I'm going to assume it may be a solid idea to invest in an OFT or something like that....?

A good tune by a professional is never a bad idea. If you're getting it tuned though you might as well fix/upgrade anything you don't like about car before going in.

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And I will throw this in, the RPMs can really fluctuate with the FA20. I’ve seen mine dip really low in slow traffic, and it will spike back up, almost stalling. I think this engine just has inconsistent vacuum pressure, or issues when the A/C compressor kicks in? It also doesn’t like to sit and idle for long. The overall theme for the twins is they are much happier being hustled around, anything else and they feel grumpy and inconsistent. [emoji28]
Oh and my car only has about 24k miles, so it’s not necessarily a mileage thing.


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Hell, I figure if your 2013 FR-S has 102,000 miles and is still running good, it deserves to idle a bit high. I'd leave it alone - ;)


humfrz

That's a pretty interesting conclusion to jump to.

I have a 2013, stock with TRD catback and intake. Bought at 42k miles, now at 54k and still idles perfectly.

It's a late model vehicle and I wouldn't tolerate anything less. I've let the car idle for 20-30 minute periods several times while working on the interior.
Dead steady idle. Fluctuation when AC comes on is pretty minor.

"If it's broke, don't fix it"?
Weird motto, but aiight.

To OP,

950rpm idle is pretty high. Like, possibly dangerously high if you have an automatic. At that engine speed, it will definitely engage the A/T and have you moving quite a bit faster than the expected 1-2mph 'parking lot creep'.
Even with a manual transmission, that might make some maneuvers slightly more difficult than necessary when shifting around at low speeds.

Aside from the technical issues, an idle of 950 would drive me up a wall.

I guess I would check obvious stuff first. If anything is unplugged or amiss in the engine bay. Maybe buy some MAF cleaner spray and do that as a sort of preventative maintenance.
Then check other items on the "regular tune-up" list, and go from there.

The aftermarket ECU note in the Carfax is interesting, but hard to know what to make of it. You might want to go back and re-read it to make sure it doesn't say something slightly different, such as "ECU reflash" by the dealership or such, which is not uncommon.

A bit weird for a regular old service shop to input "aftermarket ECU" into the service notes when changing the brakes or such. I probably wouldn't expect performance shops to participate in Carfax networks.

Especially a professional factory tune. I hear those are pretty reliable.