GR86 Rough Idle

[Hicko]

Hey folks,
My 86 has about 600 miles on it so far and I've noticed after going for a drive and being sat in neutral, handbrake on, engine idling, its not the smoothest of idles. Don't get me wrong its not awful and its mostly smooth but every other second or so th revs will dip just a little (maybe 50?) and I can feel the engine vibrate for like a split second.
I've done a fair amount of sleuthing and it does seem to be a pretty common thing even on the older models so I'm trying not to be too concerned but I figured I'd ask around with the new owners to see if anyone else has noticed this 'quirk' ?
I always let the car warm up for 15 mins before I take it out, and I mostly keep it under 4000revs for now but from time to time the temptation is too much lol

 

[Someday]

You warm it up by letting it idle for 15 minutes? That would be bad for the engine. What you describe is same as mine I think

 

[leosayer]

I always let the car warm up for 15 mins before I take it out

A complete waste of fuel and will leave a horrible smell. Just get out there and drive it as soon as you have started the engine.

I get the odd vibration from mine too - as far as I can work out it's normal behaviour. It's a highly tuned engine with limited sound proofing, not a Lexus!

 

[Hicko]

That would be bad for the engine.

Please, go on, describe how idling an engine is bad for it. I'm genuinely curious, because my WORD everyone has an opinion on engine wear in and care but almost nobody will actually provide any kind of tangible proof behind their opinions.

 

[Conscript]

Please, go on, describe how idling an engine is bad for it. I'm genuinely curious, because my WORD everyone has an opinion on engine wear in and care but almost nobody will actually provide any kind of tangible proof behind their opinions.

Low engine speed means lower oil pressure. The engine will be slower to warm up and the oil wont be moving around the engine as well while it does so. I believe with most modern engines the advice in general is to start up and move off as soon as possible, and just drive gently until up to temperature.

In reality, it probably won't do much harm to a new, modern engine to let it idle for 15 minutes before driving, but it's also not really benefiting you either and just wasting fuel. I do wonder if it might actually be the cause of your issue though - with the old car, I used to find that a battery disconnect would cause the car to idle rough afterwards. It would sort itself out eventually, and sometimes it would be quicker if you let the warm engine idle for a bit. I'm guessing that there is a 'learning' process in the ECU whereby it determines a stable idle. If you are letting the engine idle from cold, perhaps it's throwing that off? So when you get the car warm, it's idle is then a little rough.

 

[Hicko]

My reasoning for it was because I read an article from an oil inspection lab (the people who give you the materials readouts found in your oil) and the suggestion for engine break in was to drive the car normally in the full rev range (for a few reasons) but ensure that the engine is thoroughly warmed up before hand each time for at least 15 min

There’s sooo much inconsistency and armchair debate on how to break in an engine it’s just frustrating. The fact that Toyota doesn’t even mention swapping oil and filter after break in, even though it’s recommended all over the place is just another example.

 

[leosayer]

My reasoning for it was because I read an article from an oil inspection lab (the people who give you the materials readouts found in your oil) and the suggestion for engine break in was to drive the car normally in the full rev range (for a few reasons) but ensure that the engine is thoroughly warmed up before hand each time for at least 15 min

I would suggest the 15 minute warm up refers to gentle driving from cold before using full revs, not 15 minutes idling on your driveway.

 

[LukeC22]

Yeah, I had heard that boxer engines were very smooth (although this might be reserved for a Porsche flat six) so I was expecting a slightly gentler idle but mine is also kinda rough so I’m guessing it’s just another quirk of the car, like the speaker grill/A-pillar squeak.

 

[Conscript]

I would suggest the 15 minute warm up refers to gentle driving from cold before using full revs, not 15 minutes idling on your driveway.

Yeah I think maybe you might have misinterpreted it slightly @Hicko . I take that to mean. drive gently for 15 minutes, make sure the oil is up to temp, then start using the full rev range. I'd suggest maybe switch to doing that for a while, then see if it has any effect on your rough idle. Might not be the issue, but worth a shot.

I do agree though, the whole thing is a bit nebulous and full of contradictory info sometimes.

 

[leosayer]

Yeah, I had heard that boxer engines were very smooth (although this might be reserved for a Porsche flat six) so I was expecting a slightly gentler idle but mine is also kinda rough so I’m guessing it’s just another quirk of the car, like the speaker grill/A-pillar squeak.

the flat 6 in my 993 is pretty lumpy at idle... the whole car shimmies from side to side on its springs!

It does smooth out with some revs though. The GR86 is like a limo in comparison.

 

[Edgey]

What concerns me is at start up from cold the engine immediately races to around 2000rpm before dropping back to a steady idle a minute or so later. The worry is cold oil not lubricating thoroughly all the important internals, big ends etc.

 

[ZN8]

There’s sooo much inconsistency and armchair debate on how to break in an engine it’s just frustrating. The fact that Toyota doesn’t even mention swapping oil and filter after break in, even though it’s recommended all over the place is just another example.

There really is, I delved into it (both run in and a 1k oil change) and my conclusion was to ignore everyone and follow what the OEM recommends.

 

[FRAJ]

It is not the smoothest idle, but better than the previous generation.
Apart from being gentle on it from cold, I don't think there is any other warm up process required. The Engineers at Toybaru have already tested it to death in every climate in the world.

 

[Hicko]

The Engineers at Toybaru have already tested it to death in every climate in the world.

Even Scunthorpe?

 

[ZN8]

What concerns me is at start up from cold the engine immediately races to around 2000rpm before dropping back to a steady idle a minute or so later. The worry is cold oil not lubricating thoroughly all the important internals, big ends etc.

It will be fine, the engine isn't made of glass, 100 years of progress in engine and lubrication technology means we don't have to worry about it.

 

[86GR]

Yep, I think they all run a little rough.

Regarding idling to warm up, it is supposed to be bad because the fuel system will squirt in extra fuel when it is cold as it doesn’t vapourise as well. The extra fuel strips oil from the bores so you potentially get more wear. The engine will warm up much more quickly being driven under light load load than sat idling.