Rough idle?
Thread Starter
Burning Brakes
Joined: Jul 2019
Posts: 791
Likes: 679
From: New York Sitaye
Rough idle?
I know it's a pushrod small block, but there is a pretty distinct vibration at idle.
Again, I know there is a 6.2 liter motor right behind my head, but there is a very strong vibrations when stopped. The car is warm, but still within break-in period (200 miles)
Am I feeling something out of the ordinary here?
Again, I know there is a 6.2 liter motor right behind my head, but there is a very strong vibrations when stopped. The car is warm, but still within break-in period (200 miles)
Am I feeling something out of the ordinary here?
Melting Slicks
Joined: Sep 2013
Posts: 2,235
Likes: 1,160
From: montreal quebec
I noticed the same thing...it’s as sexy as hell!
Its more noticeable upon ignition,the rear actually shakes a little...I don’t know if it’s by design,one thing is for sure,the cylinder firing order seems different then my LT1 C7.
Its more noticeable upon ignition,the rear actually shakes a little...I don’t know if it’s by design,one thing is for sure,the cylinder firing order seems different then my LT1 C7.
Safety Car
Joined: Nov 2011
Posts: 3,814
Likes: 1,554
did a vid on this, run rpm's up to 2200, hold there for several minutes ( as per GM ) could just be soot build up is all, we have seen many and did this after calling then and went away
Last edited by RickConti@Coughlin; Aug 6, 2020 at 05:39 PM.
Burning Brakes
Joined: Sep 2019
Posts: 1,089
Likes: 668
From: Orange County, CA
You have seen this on sub 500 mile on the odometer, recently delivered, cars?
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Thread Starter
Burning Brakes
Joined: Jul 2019
Posts: 791
Likes: 679
From: New York Sitaye
You do realize most high performance cars are making double that these days... The 458 (a decade old now) was making 125hp per NA liter.
Once more, I realize that it's a large pushrod V8. I am just concerned something is off.
I will try keeping the revs at 1/4 throttle for a few mins to see if that clears the throat. I was worried I had a motor mount problem.
Once more, I realize that it's a large pushrod V8. I am just concerned something is off.
I will try keeping the revs at 1/4 throttle for a few mins to see if that clears the throat. I was worried I had a motor mount problem.
Safety Car
Joined: Oct 2015
Posts: 4,128
Likes: 616
From: St Louis Area IL
I know it's a pushrod small block, but there is a pretty distinct vibration at idle.
Again, I know there is a 6.2 liter motor right behind my head, but there is a very strong vibrations when stopped. The car is warm, but still within break-in period (200 miles)
Am I feeling something out of the ordinary here?
Again, I know there is a 6.2 liter motor right behind my head, but there is a very strong vibrations when stopped. The car is warm, but still within break-in period (200 miles)
Am I feeling something out of the ordinary here?
Pro
Joined: Feb 2012
Posts: 545
Likes: 85
Question: What is RPM during rough idle?
Fact: Lots of threads about LS3 rough and irregular idle (which is typically 500-550 RPM hot). Also TSB on this, which instructs technician to tell owner that this is normal.
Speculation: Low idle RPM is driven by CAFE, and rough idle is a consequence of low RPM. It's not a cam lope "rump-rump-rump...".
Fact: Lots of threads about LS3 rough and irregular idle (which is typically 500-550 RPM hot). Also TSB on this, which instructs technician to tell owner that this is normal.
Speculation: Low idle RPM is driven by CAFE, and rough idle is a consequence of low RPM. It's not a cam lope "rump-rump-rump...".
Thread Starter
Burning Brakes
Joined: Jul 2019
Posts: 791
Likes: 679
From: New York Sitaye
Every DD I even owned was a V6, turbo 4, or TT V6.
I did own a '76 Ferrari 308 for a while though. It was pretty much the other end of the spectrum. 3.0 carbureted OHC V8 with a 7700RPM redline. I got rid of the point ignition and put it an MSD system. I would turn on the ignition, give it a couple of squirts with the throttle, and it would crank right over. No choke necessary.
I was concerned that I broke a motor mount, or if Jim Bob forgot to torque something down.
Advanced
Joined: Aug 2002
Posts: 89
Likes: 29
From: LA area
Car is alive with a rough idle
I loved that in my 2001 FRC Z06.
Just sitting at a stop light was a good experience 😀
Last edited by C8HTC2020; Aug 8, 2020 at 03:24 PM.
Intermediate
Joined: Feb 2022
Posts: 26
Likes: 3
I have similar issue just dropped it off at shop it vibrates when idle and when I am say driving 40mph then accelerate it vibrates/hesitate never stalls but it vibrates/skips/gargle is the best I can describe it almost like something is missing ex a misfire or bad gas or a exhaust leak not sure if it’s normal but it’s in the shop today I have 2022 with 1700 miles on it. Hopefully they will determine the issue I don’t think it’s normal to vibrate like that when idle and acceleration any thoughts on this issue
Melting Slicks
Joined: Sep 2020
Posts: 2,839
Likes: 2,165
From: Kelso, Wa
Known problem for cars that aren't driven hard enough. If it's only 200 miles and therefore not yet broken in, it may still be in "learn mode" and should clear up soon. If not, after the 500 mile break in, do an Italian tune up.
Instructor
Joined: Jan 2022
Posts: 121
Likes: 24
From: Simi Valley,Ca
The firing order on the C8 is 1 8 7 2 6 5 4 3 and the LT1 has GM's standard firing order of 1 8 4 3 6 5 7 2 . I don't know if this will have more vibration or not.
Racer
Joined: Aug 2004
Posts: 482
Likes: 80
From: Florida, Tampa Bay
If only a tuning was availabel I'd have a diferent cam and much choppier idle. I miss my SBCs and LS1s that shook you around at a stoplight. Darn cam phasors take all the fun out of things these days.
Intermediate
Joined: Feb 2022
Posts: 26
Likes: 3
Ok so my C8 2022 appears To have a miss fire when going from V4 to V8 mode but it is not a complete Mis fire because the check engine light doesn’t come on, so my dealership is waiting to here from GM to see how to repair it, it can be a Cylinder or something else but they recommend that they keep it at the shop until they confirm the issue to prevent further issues. I should hopefully know something next Wednesday-but to recap I am getting a rough idols and vibration when it’s idol and when I accelerate midway the car staggers struggles slightly it sounds like a rumble sound then kicks in.