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Idle Glitch ??

 
Old 05-15-2019, 07:12 PM
  #21  
Dave in Pa
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Originally Posted by Velocity_Vette View Post
Have you ever owned another LS car? The LS generation of GM V8's have a different firing order than the Gen I and Gen II's prior and it can produce what is at best a 'unique' idling profile, especially if all you've ever intimately been around is LT or anything of that order.

If you have pulled codes (you can do this yourself with the car's DIC. Google it and find the YouTube video), you have no codes relating to the PCM, and the car overall appears to be running right then either (1) the car has some sort of shelf tune you weren't told about (I doubt it with just a Corsa cat back and a K&N filter, since those really aren't power mods and throwing a tune at that wastes money) or (2) at the absolute worst there's some general maintenance items lacking. On my second point for example the car may only have 31K miles and the plugs are rated to 100K but the wires are rubbing and rubber over time deteriorates exposed even sitting in a garage. If deterioration occurs in spark plugs wires it increases resistance = lesser than ideal spark.
This is great information, thanks! No I am positive the "lady" did not have anything else done to the car. As far as the Techron, I picked up two, one say fuel injector cleaner the other say fuel system cleaner. So which one should I put in the tank first? Get the feeling that they may not be/do the same thing? Thanks Dave
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Old 05-15-2019, 09:36 PM
  #22  
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Originally Posted by Dave in Pa View Post
This is great information, thanks! No I am positive the "lady" did not have anything else done to the car. As far as the Techron, I picked up two, one say fuel injector cleaner the other say fuel system cleaner. So which one should I put in the tank first? Get the feeling that they may not be/do the same thing? Thanks Dave
I'd just throw both in when I did a fill up. Put them in first, then fill the tank. One is obviously for injectors, the other is more a maintenance item to keep your gas gauge working proper. They tend to go haywire without it. Stuff builds up on the sending unit and it won't report fuel level.

I'd be checking the harmonic balancer and see if that's running true. That's the first thing I can think of that'll cause a cyclic vibration. Not a great piece of news if so, but I'd rather know.
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Old 05-16-2019, 04:50 AM
  #23  
Rob 02
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^ This gentleman has been around and knows his onions.

It is always good when he replies.
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Old 05-16-2019, 02:15 PM
  #24  
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Originally Posted by Rob 02 View Post
^ This gentleman has been around and knows his onions.

It is always good when he replies.
Well thanks, but ther'es guys on here who've forgotten 3x what I know about C5s. Even still, sometimes it's even good to get the wrong answer, if for nothing else than to eliminate possibilities.

The HB can sometimes be tough to see and be sure of. I work in a machine shop, so I look at a lot of spinning parts. It's easy to have your brain get fooled by dirt on it causing a illusion and not see the actual part running out. Seen it in videos here in the past. They're tricky. Another good thing is sometimes you can watch the belt real close (gotta check both ) but they'll have a bit of a cyclic flutter too, telling you something is wonky. Doesn't always mean it's a HB, but that is the wear part so most likely...

Having also done a lot with HP Tuners, I can say that there's a few things in a tune that can do this As a car ages the tune is no longer as ideal as it was when the motor was new. The recovery rates set for RPMs on the idla often times get to where you have a tiny bit of "hunt" for rpm. Very common when you've got a big cam and nobody set them up right. On a much smaller scale, it happens with a stock motor too.

But in his case, low miles car, one owner, with almost certainly the OEM balancer, and he just did some high rpm runs.... That's where I would start.
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Old 05-16-2019, 03:43 PM
  #25  
Dave in Pa
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Originally Posted by K-Spaz View Post
Well thanks, but ther'es guys on here who've forgotten 3x what I know about C5s. Even still, sometimes it's even good to get the wrong answer, if for nothing else than to eliminate possibilities.

The HB can sometimes be tough to see and be sure of. I work in a machine shop, so I look at a lot of spinning parts. It's easy to have your brain get fooled by dirt on it causing a illusion and not see the actual part running out. Seen it in videos here in the past. They're tricky. Another good thing is sometimes you can watch the belt real close (gotta check both ) but they'll have a bit of a cyclic flutter too, telling you something is wonky. Doesn't always mean it's a HB, but that is the wear part so most likely...

Having also done a lot with HP Tuners, I can say that there's a few things in a tune that can do this As a car ages the tune is no longer as ideal as it was when the motor was new. The recovery rates set for RPMs on the idla often times get to where you have a tiny bit of "hunt" for rpm. Very common when you've got a big cam and nobody set them up right. On a much smaller scale, it happens with a stock motor too.

But in his case, low miles car, one owner, with almost certainly the OEM balancer, and he just did some high rpm runs.... That's where I would start.
Thanks a lot!!!!!!!!! Dave
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Old 05-17-2019, 12:10 AM
  #26  
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Originally Posted by K-Spaz View Post
Well thanks, but ther'es guys on here who've forgotten 3x what I know about C5s. Even still, sometimes it's even good to get the wrong answer, if for nothing else than to eliminate possibilities.

The HB can sometimes be tough to see and be sure of. I work in a machine shop, so I look at a lot of spinning parts. It's easy to have your brain get fooled by dirt on it causing a illusion and not see the actual part running out. Seen it in videos here in the past. They're tricky. Another good thing is sometimes you can watch the belt real close (gotta check both ) but they'll have a bit of a cyclic flutter too, telling you something is wonky. Doesn't always mean it's a HB, but that is the wear part so most likely...

Having also done a lot with HP Tuners, I can say that there's a few things in a tune that can do this As a car ages the tune is no longer as ideal as it was when the motor was new. The recovery rates set for RPMs on the idla often times get to where you have a tiny bit of "hunt" for rpm. Very common when you've got a big cam and nobody set them up right. On a much smaller scale, it happens with a stock motor too.

But in his case, low miles car, one owner, with almost certainly the OEM balancer, and he just did some high rpm runs.... That's where I would start.
GREAT info !!...when you speak of "As a car ages the tune is no longer as ideal as it was when the motor was new" I attended an auto diagnostic seminar years back taught by Dr. Norman "Doc" Nall....Doc Nall has been an automotive instructor for over 40 years and was instrumental in the development of OBD 2 back in the 90's working with the EPA...he told us and it was new to me that the automotive engineers "tweak" the PCM as a car ages...I guess things like injector pulse width and some other things...he didn't say exactly what...those things are "proprietary info" by the manufacturers !!
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Old 05-17-2019, 12:20 AM
  #27  
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One thing most over looked is the air filter...I had issues with real low idle speed and found completely clogged air filter. Easy check.
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Old 05-17-2019, 01:13 AM
  #28  
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