Power loss

[Antonio757]

I have a 2002 Chevy Tahoe and I just replaced the exhaust system with a maganaflow. The problem I’m have is that I’m experiencing a major power loss when I’m accelerating after being stopped. Any idea as to what may cause this?

 

[B-train]

Are there any engine codes present? Maybe fuel pressure? Also, a high flow exhaust may make the truck drive diffently than the OEM. Are you sure that you're just not hearing more noise than normal, leading you to believe you should be going faster?

 

[StormTrooprSubZ71]

If the problem started after your exhaust install check your O2 sensors, did they leave them unconnected. Do you still have your catalytic convertor installed? If your exhaust is too free flowing you might not have enough back pressure.

 

[Marky Dissod]

I have a '02 Tahoe and I just replaced the exhaust system with a magnaflow.
The problem I’m have is that I’m experiencing a major power loss when I’m accelerating after being stopped.
Any idea as to what may cause this?

Can you compare the OE exhaust system to the magnaflow?
If your exhaust is too large in the wrong place(s) it may not have enough SCAVENGING.

 

[Antonio757]

Are there any engine codes present? Maybe fuel pressure? Also, a high flow exhaust may make the truck drive diffently than the OEM. Are you sure that you're just not hearing more noise than normal, leading you to believe you should be going faster?

There’s no engine code but the service engine light is blinking. The scanner from Auto Zone didn’t pick any up. Not sure why. It’s definitely a problem. I filled up my tank about 4 pm yesterday and ran out of gas 10 am this morning.

 

[Antonio757]

Can you compare the OE exhaust system to the magnaflow?
If your exhaust is too large in the wrong place(s) it may not have enough SCAVENGING.

I’m not sure what that means exactly but I had it installed by a shop.

 

[Antonio757]

If the problem started after your exhaust install check your O2 sensors, did they leave them unconnected. Do you still have your catalytic convertor installed? If your exhaust is too free flowing you might not have enough back pressure.

The O2 sensors are new and the cats are new also. I went through a tank of gas in less than 24 hours.

 

[Joseph Garcia]

I do not believe that the replacement of only the muffler itself would cause any backflow pressure change issues that would significantly cause negative performance.

I believe that something else changed with the installation of the muffler. If you are getting a service engine light, there must be underlying trouble codes that are causing it to light. I'm not sure what scanner you are using, but if it is not a full service bi-directional scanner, it is probably missing the trouble codes that are present.

 

[Fless]

I do not believe that the replacement of only the muffler itself would cause any backflow pressure change issues that would significantly cause negative performance.

I believe that something else changed with the installation of the muffler. If you are getting a service engine light, there must be underlying trouble codes that are causing it to light. I'm not sure what scanner you are using, but if it is not a full service bi-directional scanner, it is probably missing the trouble codes that are present.

^^x2^^

Any issues prior to the exhaust install?
How many miles or hours did it take to drink the full tank of fuel?
Were the catalytic converters retained?
Are the oxygen sensors connected and working?

 

[strutaeng]

but the service engine light is blinking. The scanner from Auto Zone didn’t pick any up.

Service Engine blinking means you have a misfire and running the vehicle like that will inevitably damage your new catalytic converters!

So try to figure out why you have a misfire is your underlying issue, but there may be more issues. Once you fix that, your power will come back.

 

[Antonio757]

I do not believe that the replacement of only the muffler itself would cause any backflow pressure change issues that would significantly cause negative performance.

I believe that something else changed with the installation of the muffler. If you are getting a service engine light, there must be underlying trouble codes that are causing it to light. I'm not sure what scanner you are using, but if it is not a full service bi-directional scanner, it is probably missing the trouble codes that are present.

The check engine light was on prior to the cat and muffler installation. One of the codes it was reading at first was due to a clog cat.

 

[Joseph Garcia]

The check engine light was on prior to the cat and muffler installation. One of the codes it was reading at first was due to a clog cat.

Are you saying that you changed a cat in addition to changing the muffler?

 

[strutaeng]

Are you saying that you changed a cat in addition to changing the muffler?

Maybe he changed the cats because they were damaged because he had a misfire before?

Argh...I hate when we don't get the whole story or history from OPs.

Nothing against you OP, but it's always best to give us big picture and background, then explain your problem so folks here can understand what's going on.

 

[Scottydoggs]

There’s no engine code but the service engine light is blinking. The scanner from Auto Zone didn’t pick any up. Not sure why. It’s definitely a problem. I filled up my tank about 4 pm yesterday and ran out of gas 10 am this morning.

flashing cel means multiple misfires. you either need a tune up super bad, or the cats are clogged up. if the lights flashing fix it asap. pretty much means theres a catastrophic event going on.

next time it flashes, scan the truck running, dont turn it off or you'll clear the pending code making the cel flash.

 

[Fless]

flashing cel means multiple misfires. you either need a tune up super bad, or the cats are clogged up. if the lights flashing fix it asap. pretty much means theres a catastrophic event going on.

next time it flashes, scan the truck running, dont turn it off or you'll clear the pending code making the cel flash.

^^x2^^

Using that much fuel seems to indicate that it's dumping fuel into the cylinders. Doing that will kill the (new) cats, and soon. Based on the plugged cat that you replaced, this has been going on for a while. Should look at misfire counters, fuel trims and fuel management to verify. Might need someone with diagnostic knowledge to put their hands on it.

 

[Antonio757]

flashing cel means multiple misfires. you either need a tune up super bad, or the cats are clogged up. if the lights flashing fix it asap. pretty much means theres a catastrophic event going on.

next time it flashes, scan the truck running, dont turn it off or you'll clear the pending code making the cel flash.

I’m thinking the misfires are from my leaking valve covers. Getting them fixed asap!

 

[Mudsport96]

Bad crank sensor, coils, plugs, wires, injectors, cam sensor or intake gaskets. Those are really the top things that will cause misfires.
Leaking valve covers would have to leak so much oil that they would set the exhaust manifolds on fire before they would cause a misfire.

 

[blondie70]

I just had the oem muffler removed and a Magnaflow installed yesterday. Truck runs great Good luck with yours.

 

[Antonio757]

Maybe he changed the cats because they were damaged because he had a misfire before?

Argh...I hate when we don't get the whole story or history from OPs.

Nothing against you OP, but it's always best to give us big picture and background, then explain your problem so folks here can understand what's going on.

Yes, that cat and muffler has be changed. I think it the leak I’ve found from the value cover in the left side.

 

[RST Dana]

Yes, that cat and muffler has be changed. I think it the leak I’ve found from the value cover in the left side.

Valve cover leak won’t cause a misfire or a CEL. Something else is the issue.