96 lt4 sluggish. No bottom end
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Heel & Toe
Joined: Jun 2025
Posts: 23
Likes: 0
96 lt4 sluggish. No bottom end
Picked up a 96 lt4 with 80k on the clock. Have had a 96 auto car and wanted a bit more power and a stick. Car drives and operates perfectly other than is an absolute dog. I expected to be able to at least bark the tires some while rolling in 1st and nailing it but it is quite boring. I dont notice any more pickup than the auto car and maybe even less.
it will peel out if i rev and dump the clutch but still no setting back in the seat feel to it. I have plenty experience with cars to know it should do better than this.
There are no codes. have gone through the fuel system. Upper 30s psi when full throttle. The cats arent clogged (at least with a vacuum gauge test). Newer plug wires. Airways look fine. Maf is clean. Spark advance is 14 at idle. Upper 30s under wot. The tps reads 100 percent at wot.
I do have a scanner that gives real time data of sensors but i dont know what alot of that stuff is. What else could it be? The car runs like a top through the rpm band, just slowly. If i didnt know better, id just say these cars are pigs, but with 330 hp and 3.45 gears it ought feel better than my auto car. The opti looks original but no misfires, sputters, or other weird stuff.
it will peel out if i rev and dump the clutch but still no setting back in the seat feel to it. I have plenty experience with cars to know it should do better than this.
There are no codes. have gone through the fuel system. Upper 30s psi when full throttle. The cats arent clogged (at least with a vacuum gauge test). Newer plug wires. Airways look fine. Maf is clean. Spark advance is 14 at idle. Upper 30s under wot. The tps reads 100 percent at wot.
I do have a scanner that gives real time data of sensors but i dont know what alot of that stuff is. What else could it be? The car runs like a top through the rpm band, just slowly. If i didnt know better, id just say these cars are pigs, but with 330 hp and 3.45 gears it ought feel better than my auto car. The opti looks original but no misfires, sputters, or other weird stuff.
Advanced
Joined: Jul 2016
Posts: 66
Likes: 12
Lt-4 manual
Picked up a 96 lt4 with 80k on the clock. Have had a 96 auto car and wanted a bit more power and a stick. Car drives and operates perfectly other than is an absolute dog. I expected to be able to at least bark the tires some while rolling in 1st and nailing it but it is quite boring. I dont notice any more pickup than the auto car and maybe even less.
it will peel out if i rev and dump the clutch but still no setting back in the seat feel to it. I have plenty experience with cars to know it should do better than this.
There are no codes. have gone through the fuel system. Upper 30s psi when full throttle. The cats arent clogged (at least with a vacuum gauge test). Newer plug wires. Airways look fine. Maf is clean. Spark advance is 14 at idle. Upper 30s under wot. The tps reads 100 percent at wot.
I do have a scanner that gives real time data of sensors but i dont know what alot of that stuff is. What else could it be? The car runs like a top through the rpm band, just slowly. If i didnt know better, id just say these cars are pigs, but with 330 hp and 3.45 gears it ought feel better than my auto car. The opti looks original but no misfires, sputters, or other weird stuff.
it will peel out if i rev and dump the clutch but still no setting back in the seat feel to it. I have plenty experience with cars to know it should do better than this.
There are no codes. have gone through the fuel system. Upper 30s psi when full throttle. The cats arent clogged (at least with a vacuum gauge test). Newer plug wires. Airways look fine. Maf is clean. Spark advance is 14 at idle. Upper 30s under wot. The tps reads 100 percent at wot.
I do have a scanner that gives real time data of sensors but i dont know what alot of that stuff is. What else could it be? The car runs like a top through the rpm band, just slowly. If i didnt know better, id just say these cars are pigs, but with 330 hp and 3.45 gears it ought feel better than my auto car. The opti looks original but no misfires, sputters, or other weird stuff.
Last edited by z06 guy; Jun 6, 2025 at 10:19 PM. Reason: Addition
Drifting
Joined: Feb 2008
Posts: 1,537
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From: NE Ohio
2024 C4 of the Year Finalist - Unmodified
Thread Starter
Heel & Toe
Joined: Jun 2025
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thats what i was expecting having owning other sports cars that will with even less hp than this. The fuel filter is the very next thing. I havent done it yet but am not expecting that to fix it.
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Heel & Toe
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Le Mans Master
Joined: Feb 2000
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From: Epping NH
Yeah, the stock fuel pressure on an LT4 runs between 41 and 47 psi. I'm assuming the basics have already been checked, spark plugs, wires, fuel filter. The MAF could definitely be the issue if it is aftermarket.
The LT4 is underrated at 330 hp. In reality, it is more like 345 based on a lot of dyno results posted over the years. GM downplayed it a bit because, back in 1997, the new LS1 in the C5 was not quite up to par and came in under the LT4 in horsepower. And let's be honest, who was going to buy a brand new C5 if the outgoing C4 LT4 had more power? So GM marketing conveniently fudged the LT4 hp numbers down.
Personally, I ran a 12.9 at 109 MPH in the 1/4 back in the late 90s. It is easily a 4.5 to 5 second car 0 to 60. The car should push you back in the seat launching from a dead stop.
The LT4 is underrated at 330 hp. In reality, it is more like 345 based on a lot of dyno results posted over the years. GM downplayed it a bit because, back in 1997, the new LS1 in the C5 was not quite up to par and came in under the LT4 in horsepower. And let's be honest, who was going to buy a brand new C5 if the outgoing C4 LT4 had more power? So GM marketing conveniently fudged the LT4 hp numbers down.
Personally, I ran a 12.9 at 109 MPH in the 1/4 back in the late 90s. It is easily a 4.5 to 5 second car 0 to 60. The car should push you back in the seat launching from a dead stop.
Pro
Joined: Oct 2012
Posts: 580
Likes: 121
From: Grapevine TX
Probably not it but something easy to check, make sure the oil isn't overfilled. I saw this once a long time ago where someone kept adding oil and the car was real sluggish due to the crank whipping through all that oil.
Instructor
Joined: Aug 2024
Posts: 108
Likes: 71
The LT4 definitely pulls stronger up top making it feel like it has less torque than it does. Your timing seems correct. 37-38* advance is right where it should be. I’d put a stock MAF on it and see what that does. Here’s Brandon’s (he’s on the forum) LT4 acceleration on a stock car with Corsa exhaust. Does this look like your acceleration?
Thread Starter
Heel & Toe
Joined: Jun 2025
Posts: 23
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The LT4 definitely pulls stronger up top making it feel like it has less torque than it does. Your timing seems correct. 37-38* advance is right where it should be. I’d put a stock MAF on it and see what that does. Here’s Brandon’s (he’s on the forum) LT4 acceleration on a stock car with Corsa exhaust. Does this look like your acceleration? https://youtu.be/1KhUPwgqJBM?feature=shared
these are low 13 second cars. They got to have some launch to them or they would never make it. I think the cats are partially plugged. Got to check
Instructor
Joined: Mar 2021
Posts: 169
Likes: 25
I'd change that maf and get a scan on it. Depending on how long it sat before you bought it, gas mightve turned or had 87 put in it.
Another couple things to consider, auto cars will always feel faster from from take off due to the first gear and torque multiplication from the stall. Just stomp and go. Also, here in phx, it's over 130 on the streets right now and my 5spd Z24 DD that feels pretty peppy and quick, feels like a dog now sucking in all that hot air and the tires nice and hot and grippy. Food for thought.
Another couple things to consider, auto cars will always feel faster from from take off due to the first gear and torque multiplication from the stall. Just stomp and go. Also, here in phx, it's over 130 on the streets right now and my 5spd Z24 DD that feels pretty peppy and quick, feels like a dog now sucking in all that hot air and the tires nice and hot and grippy. Food for thought.
Burning Brakes
Joined: Jun 2022
Posts: 845
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From: Florida
I think a better measure of torque on the LT1/4 engines would be a rolling start in first gear at WOT. Does it bog down, does it go at a decent rate, or does it smoke the tires? In doing this, things like clutch dumping are factored out, so it's really all engine.
Doing this in my own car, the tires never spin. Rather the car accelerates at a decent rate. Nothing mind blowing or that makes me say "wow".
For comparison... Doing the same in my former 2009 Vette with traction off was a dangerous endeavor. The car would be all over the place. My 88 Trans Am GTA would behave similarly, slightly less violent.
Intake manifold design has a lot to do with bottom end torque. The LT1/4 engines are at the opposite extreme of the TPI engines. They gave up low end torque for higher RPM power. Very short vs very long runners.
I wish I could drive a completely stock and properly working LT4 so I could compare to mine.
Doing this in my own car, the tires never spin. Rather the car accelerates at a decent rate. Nothing mind blowing or that makes me say "wow".
For comparison... Doing the same in my former 2009 Vette with traction off was a dangerous endeavor. The car would be all over the place. My 88 Trans Am GTA would behave similarly, slightly less violent.
Intake manifold design has a lot to do with bottom end torque. The LT1/4 engines are at the opposite extreme of the TPI engines. They gave up low end torque for higher RPM power. Very short vs very long runners.
I wish I could drive a completely stock and properly working LT4 so I could compare to mine.