No Power? slow as a dog!

[MN MUDDER]

I got a 2000 Silverado. 5.3 that I cannot figure out why it has no power. I have a obd2 scanner that I have read and fixed problems through out the years. Recently I have replaced the fuel and air filter, plugs, maf, and 2 new knock sensors and harness( the ses comes on every now and then from that??) It has a flowmaster exhaust and a leveling kit. But The truck will be dead slow off the line and is almost dangerous. I hit the pedal and nothing happens. It's delayed throughout first gear than shifts and takes off like a rocket. It's really starting to bug me. Any help would be great, thanks

[MN MUDDER]

Really? Why's that?

Really? It's just a super 44 muffler

[02suburbanZ71]

Really? Why's that?

Really? It's just a super 44 muffler

5.3's need the stock exhaust because they need lots of back pressure do to the fact they make all torque at 4400. Put the factory exhaust on and unplug the battery.... See what happens. Lots of 5.3's lose low end torque with after market mufflers. Thats why i wont change mine

[MN MUDDER]

Well I have buddies with 5.3s that just cut out their mufflers and replaced with a straight pipe or glass pack and they claim it made really no difference with there power. Is it just a flowmaster thing?

[Chris]

5.3's need the stock exhaust because they need lots of back pressure do to the fact they make all torque at 4400. Put the factory exhaust on and unplug the battery.... See what happens. Lots of 5.3's lose low end torque with after market mufflers. Thats why i wont change mine

FALSE.

 

The muffler you chose matters. Flowmasters are common for robbing power on mostly stock applications. My 6.0 makes the torque in the same area as the 5.3. Most LS engines make the peak torque around 4000-4500. I have had aftermarket exhaust for years. Only lost power with a Flowmaster

[MN MUDDER]

Hmmm... Do you guys think it could be anything else but the muffler? It makes sense but I'm just weighing out my options

[Chris]

Unless you have internal engine issues, you are restricting the exhaust gas leaving.

[Doug_Scott]

Once the engine hits over 4k in first gear, does it start to pull better? Engine does not care what gear you are in(realistically speaking, not talking about being in high gear at a dead stop). What you may want to look into is getting a tune for the engine. There are torque management hits in the stock ECM to reduce torque in low gear. Ever notice it is not easy to spin the tires on dry clean pavement?

 

 

edit to remove double text

[Doug_Scott]

Unless you have internal engine issues, you are restricting the exhaust gas leaving.

 

This does not really make any sense. Did you get the wording correct for what you wanted to say? Adding a free flowing exhaust does not really restrict the exhaust gas leaving.

[Chris]

No. I didnt. Long day and I'm in bed. The flowmaster is more restrictive. I had one myself and consider it a 3 year mistake. It sounded decent but I did lose some power. If the muffer is the only modification on the truck it is likely the issue. Given the age something else internally could be a problem as well. A tune will help if the engine is in good health. I had a tune with the flowmaster and it felt better after I got rid of the flowmaster.

[Carder09]

Time for some LT headers with custom dual exhaust dumped before the axle!

[02suburbanZ71]

How about a seafoam treatment?

[MN MUDDER]

Already did seafoam, and yes it pulls a lot harder after 4 grand. It sounds great, but I have shut for lower end torque. I used to be able to spin my 35s on dry pavement but now it won't even think about doing it on wet pavement.

[desrtrat]

5.3's need the stock exhaust because they need lots of back pressure do to the fact they make all torque at 4400.

where did you come up with that info from the last thing you want IS LOTS OF BACK PRESSURE...

[kstruckcountry]

I doubt the muffler made it that bad... Has it always been like this? Or just after the muffler went on?

 

From the description it could be many things...