LS1 sluggish at low RPMs
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Teching In
Joined: Sep 2004
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LS1 sluggish at low RPMs Guys,
My 99 SS LS1 runs very sluggish in 6th gear when trying to accelerate from 70 mph. When I try to pick up speed, it feels like it is missing....
NO Codes.....
Any thoughts?????
My 99 SS LS1 runs very sluggish in 6th gear when trying to accelerate from 70 mph. When I try to pick up speed, it feels like it is missing....
NO Codes.....
Any thoughts?????
I'd start with the regular maintenance and tune-up to ensure the engine is getting the proper fueling, air, spark, etc. If that doesn't help, I'd consider down-shifting and putting the engine higher into its powerband 
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If the air filter is dirty replace it,and spray the MAFS sensor with some MAFS cleaner.
And check/change your spark plugs. Also Pull the intake and clean it out with some carburetor cleaner, and on the heads do the same with the intake runners. After you get it all back together install a catch-can. it should run smoother in 6th.
Or you can just down-shift into 5th, or 4th .
or 3rd 
i love having 4 gears to chose from when passing...hell 5 if you're doing ~50
uncorking the TDs at 4000rpm to pass someone is GREAT!!!
untill you get pulled over 20miles later
i love having 4 gears to chose from when passing...hell 5 if you're doing ~50
uncorking the TDs at 4000rpm to pass someone is GREAT!!!
untill you get pulled over 20miles later
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From: Denver International Airport, Colorado USA
That is very common when using a .50 overdrive and attempting to accelerate. A LS1 is barely making ~100 Hp at that Rpm and gear.
If you have tuning software and log it, you will see that your MAP (or load) is actually quite high at that Rpm when you attempt to accelerate. In essence you are lugging the engine.
Having two overdrives in a car with as much power as a LS1 is a real luxury. In the 'old days' people who have loved to have had that. It lets you add aggressive gearing (3.73-4.10) and still cruise at relatively low Rpms at highway speeds.
You simply can not use a 2nd overdrive to accelerate your engine. I have seen the MAP go to its limits when you try it. It probably is not good for the engine. Down-shifting is what you have to do.
Hope that helps. Good luck, and take care of that engine!
..WeathermanShawn..
If you have tuning software and log it, you will see that your MAP (or load) is actually quite high at that Rpm when you attempt to accelerate. In essence you are lugging the engine.
Having two overdrives in a car with as much power as a LS1 is a real luxury. In the 'old days' people who have loved to have had that. It lets you add aggressive gearing (3.73-4.10) and still cruise at relatively low Rpms at highway speeds.
You simply can not use a 2nd overdrive to accelerate your engine. I have seen the MAP go to its limits when you try it. It probably is not good for the engine. Down-shifting is what you have to do.
Hope that helps. Good luck, and take care of that engine!
..WeathermanShawn..
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Teching In
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I have a almost the same problem My car also does something similar but when its cold.. when in turn it on its good for about 15 sec and then it start feel sluggish. Everything mechanically is great and. I got new spark plugs, spark plug wires, the ignition coils and wires are good, compression is good, fuel pressure is good, new fuel filter also there is no vaccum leaks and all ground cables are good... but It still not 100% good but I really don't know what it can be anymore
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One of my most consistent tests I do to identify ignition components being faulty is drive a car at high load at low rpm. If I have worn plugs or a weak coil it'll show when I do this.
So also as stated try a set of plugs, maybe wires if you haven't changed them in a while. If it still does it you could have a weak coil.
You really need to watch it on a misfire monitor though, it's always hard guessing over the internet if what you say feels like a misfire is for sure a misfire.
I was gonna say check the cats for being clogged but if it comes and goes it may be fuel supply causing it. Try the fuel filter first, if that doesn't help check the fuel pressure and flow, I test flow by opening the bypass valve on my tester with the car running. It should supply enough fuel to put a good stream out of the tester and the car continue running.
TECH Addict
Joined: Mar 2013
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Hook up a scanner and watch the timing, it may be pulling timing at times causing your problem. I had something very similar, was pulling 8 degrees at times. The intake was CAKED thick with carbon.
Teching In
Joined: Dec 2017
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I also think its the timing because it's not constant it just does it like 3 minutes after I turn on my car and also when its already warmed up. Do you think that can cause a raw gas smell at the exhast??
Joined: Aug 2007
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From: Turnin' Wrenches Infractions: 005
That is very common when using a .50 overdrive and attempting to accelerate. A LS1 is barely making ~100 Hp at that Rpm and gear.
If you have tuning software and log it, you will see that your MAP (or load) is actually quite high at that Rpm when you attempt to accelerate. In essence you are lugging the engine.
Having two overdrives in a car with as much power as a LS1 is a real luxury. In the 'old days' people who have loved to have had that. It lets you add aggressive gearing (3.73-4.10) and still cruise at relatively low Rpms at highway speeds.
You simply can not use a 2nd overdrive to accelerate your engine. I have seen the MAP go to its limits when you try it. It probably is not good for the engine. Down-shifting is what you have to do.
Hope that helps. Good luck, and take care of that engine!
..WeathermanShawn..
If you have tuning software and log it, you will see that your MAP (or load) is actually quite high at that Rpm when you attempt to accelerate. In essence you are lugging the engine.
Having two overdrives in a car with as much power as a LS1 is a real luxury. In the 'old days' people who have loved to have had that. It lets you add aggressive gearing (3.73-4.10) and still cruise at relatively low Rpms at highway speeds.
You simply can not use a 2nd overdrive to accelerate your engine. I have seen the MAP go to its limits when you try it. It probably is not good for the engine. Down-shifting is what you have to do.
Hope that helps. Good luck, and take care of that engine!
..WeathermanShawn..
It shouldn't feel like it's missing though. I agree with the above comments that the gear is too high for that speed and you should downshift but it should have trouble accelerating in that gear at that speed but it should be smoothly.
One of my most consistent tests I do to identify ignition components being faulty is drive a car at high load at low rpm. If I have worn plugs or a weak coil it'll show when I do this.
So also as stated try a set of plugs, maybe wires if you haven't changed them in a while. If it still does it you could have a weak coil.
You really need to watch it on a misfire monitor though, it's always hard guessing over the internet if what you say feels like a misfire is for sure a misfire.
One of my most consistent tests I do to identify ignition components being faulty is drive a car at high load at low rpm. If I have worn plugs or a weak coil it'll show when I do this.
So also as stated try a set of plugs, maybe wires if you haven't changed them in a while. If it still does it you could have a weak coil.
You really need to watch it on a misfire monitor though, it's always hard guessing over the internet if what you say feels like a misfire is for sure a misfire.
