LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

How Smooth does your LT1 idle?

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Old 04-28-2005, 05:23 PM
  #16  
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Re: How Smooth does your LT1 idle?

Originally Posted by Randy L
I was wondering if I have a problem or if it was normal. I notice that my '97 LT1 doesn't idle "smooth as butter". The tach shows a steady 800RPM, but I can sense a slight "roughness" in the idle, which may be interpreted as a slight miss. I recently changed the Opti, serpentine belt, plugs and wires, and water pump all at the same time. It idled the same way before the service. It doesn't sputter or try to die on me..I just never really noticed that it idled "rough". No SES codes are on either.
While at speed, it runs great.
I know exactly what you're talking about...

I have a 111,600 mile '95 A4 Z28 (bolt-on only) that runs perfectly, but the idle is a bit rough. Like you, my tach reads steady, but the car does have a slight "shake" to it (especially when fully-warmed up). Although, it never feels like it's going to sputter or die like you said. And I've had all the usual service done too (plugs, wires, fuel/intake flush, opti, etc.). But yeah, it always idled the same way even before I had all that stuff changed too.

Personally, I just think this is typical of LT1's in general. I've also heard many people say this about this motor. Think about it, it is a Small Block 350. It's not going to idle as smoothly as the newer designed V8's of today. And honestly, the LS1 in my sig idles noticeably smoother. In fact, the LS1's were designed to have a smoother/quieter idle than LT1's had.

If the car drives perfectly and holds a solid/steady idle (and does not show any misfire codes), then don't worry about...

Mike
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Old 04-28-2005, 05:24 PM
  #17  
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Re: How Smooth does your LT1 idle?

mine seems to idle fine, i mean, i have to flick the gauge cluster to get the needles to start moving(dont know why), its the accelerating part that is ****ty
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Old 04-28-2005, 08:08 PM
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Re: How Smooth does your LT1 idle?

Originally Posted by BUBBA
If your "tach" is reading 800 and the tachs usually read a couple hundred high, I'd guess that you might actually be idling too slow. My pcm is progsrammed to idle at around 950 with my little bitty cam and if idles quite nicely.

However, if I was reading 950 on my tach, I would, in reality, be idling around 750 which would probably mess with my idle. (M-6) JMHO
Yup, my tach is about 200rpm high. Incidentally, so is the one in my Caprice. Hmm...
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Old 04-28-2005, 09:09 PM
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Re: How Smooth does your LT1 idle?

lopes and chops like a sonbitch ,altho it is pretty consistant. Hotcam with car programmed to idle at 750 , i love the sound !!!!
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Old 04-28-2005, 10:24 PM
  #20  
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Re: How Smooth does your LT1 idle?

noticed tonight that my car idles crappy as hell. I mean it idles at 500-600 with an occasional quiver. ... what could be the problem?
new opti,wires,plugs,coil,fuel filter..
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Old 04-29-2005, 01:24 AM
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Re: How Smooth does your LT1 idle?

when my car idles it'll give a little shake here and there, but the tach is steady. looked at it with my autotap and no miss fires, no knock, 0 change in rpm.
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Old 04-30-2005, 03:06 AM
  #22  
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Re: How Smooth does your LT1 idle?

What got me to wondering if I actually had a miss was that even though the tach showed rock steady, I felt that SLIGHT shake and the oil pressure gauge jumped up & down noticeabley. Could be that the OPG sending unit is a little dirty.
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Old 05-07-2005, 09:22 AM
  #23  
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Re: How Smooth does your LT1 idle?

Originally Posted by Randy L
What got me to wondering if I actually had a miss was that even though the tach showed rock steady, I felt that SLIGHT shake and the oil pressure gauge jumped up & down noticeabley. Could be that the OPG sending unit is a little dirty.
There is a delay circuit built into the tach that keeps it from snapping around with quick changes in RPM (probably because GM couldn't get it to idle dead smooth), so the oil pressure sending unit is actually registering the slight changes in RPM.
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