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I have a 2016 Z51. The idle seems a little rough. Is that normal? Anyone experience the same situation. Probably could live with it, dread bringing it to a dealer even under warranty.
Normal. Rest assured that if there were ANY misfire, the computer would flash the "Check Engine Soon" each time and it will light it if the problem is persistent.
(Now if the light is on that's not normal, of course).
If it's really bothersome GM can do some remediation like padded shims, at least on the Cadillacs, not sure about the LT4.
But if you view it as a mark of a performance engine (and it's the performance camshaft that causes a slightly unstable idle), and know it's "right", it may not bother you at all! Doesn't bother me!
Open the hood and is the engine shaking at all when it runs rough? The previous owner of my car was a moron and the air filter was filthy. I replaced it with a K&N drop in AND cleaned the mass air sensor with electronics cleaner (they also make stuff branded for air sensor cleaning) I would give that a try and see what it does.
Fixed my problem and hesitation after both. Now it just runs like it should with MINIMAL built in rough idle as other has stated...
Put a race cam in and you'll find out what rough is ��
LOL! Back in the day I had a '56 Chevy that I built a 283 with a Duntov "30/30" cam for ... Sounded like a thrashing machine, and the C7 feels like a purring kitten in comparison...
^^
Yep, diesels don't have much intake exhaust valve overlap as they never get to the rpm where it's needed! That is what causes some of the "roughness in idle" in a high performance engine.
Just checked, and 41 years ago a 350 cid 1977 Vette had 180 hp and if you had the high performance engine L82 a "whopping 210 hp!" Some of the worst years for Vette engines; EPA rules, exhaust air injection, lean mixtures etc. (Had to modify the engine in my 1974 260Z, the start of exhaust air pumps, hot water in the intake manifold, lean metering needles in those twin Hitachi SU's etc. Headers that also eliminated the air pump, blocking the intake hot water, richer metering needles and my first use on Mobil 1 in those carb dashpots - solved the performance problems and provided more power!)
Now if you had a "real Vette" like a smaller 1957 283 cid engine with a Duntov cam you could get 275 hp! That cam had 78 degrees of overlap meaning the Intake valve started to open while the Exhaust valve was still open for 78 degrees of crank rotation! Talk about a bad idle! We loved it "In The Day!"
What is amazing to me, is the LT1 gets 460 net HP from 376 cid with low emissions and a reasonable idle that Duntov would have given his right arm to have!
PS: Joe, more info for you to google, like overlap, lobe separation, duration etc- if you want to learn!
Why would an intake valve start to open when the exhaust valve is still open? Doesn't fit the classic basic explanation of a 4 cycle engine with separate Intake/Compression/Power/Exhaust stokes! Because at high rpm it helps to fill the cylinder with more air-fuel! At low rpm makes the engine inefficient and stumble. Therefore high performance engines have a rougher idle that a grocery getter that never sees high rpm. However the overlap in the C7 cam is no where near that of the old Duntov cam. At idle that cam caused more emissions as well, which is why that dog of a '77 Vette engine was way down on power!
04-25-2018, 11:44 AM
Car Idle
