2014 5.3 cat's plugged? limp mode under load at 3000 rpm

[4banger]

My buddies truck, he's on a budget so looking for more info on this, the stealership wants $4900 cad to fix. 

 

Here's what happens, towing the cargo trailer, gets to about 80-90 kmh (50 mph) and try to push it any harder or when hills come and needs to add power it goes into limp mode and speeds drop right off, seems to be around 3000 rpm, runs great under that, throw the hazards on and limp up the hills getting passed by everyone. He loves his truck and even more that it got him home from a long hunting trip even thought it was a slower trip home dealing with this.

 

What's the cheapest easiest solution? He has a mechanic that can do most things but was having trouble figuring it out so took to dealership who said it was cat's and it will be near $5k fix.

 

shoot just realized I dropped this into the wrong sub-forum?

Edited November 10, 2023 by 4banger

[Bikerjon]

Create an opening in the exhaust before the converters. Plugged/restricted converters will cause excessive back pressure in the exhaust system. I would suggest loosening the nuts on the studs at the exhaust manifolds except that they will be rusted solid and probably break off causing you more problems. I have used a hack on older vehicles when I knew the converters were plugged. Torch a couple holes in the exhaust pipes before the up stream converters to relieve the back pressure, You can then test drive the truck and verify the condition. I am not suggesting that you use this hack but I have done this successfully on some older vehicles. You could then decide if you drive the truck in this condition or replace the cats. $4900.00 sounds like a hell of alot of money for this repair. I bet a good exhaust shop could do this for a lot less with after market cats.

[Silverado4x4]

19 hours ago, Bikerjon said:

Create an opening in the exhaust before the converters. Plugged/restricted converters will cause excessive back pressure in the exhaust system. I would suggest loosening the nuts on the studs at the exhaust manifolds except that they will be rusted solid and probably break off causing you more problems. I have used a hack on older vehicles when I knew the converters were plugged. Torch a couple holes in the exhaust pipes before the up stream converters to relieve the back pressure, You can then test drive the truck and verify the condition. I am not suggesting that you use this hack but I have done this successfully on some older vehicles. You could then decide if you drive the truck in this condition or replace the cats. $4900.00 sounds like a hell of alot of money for this repair. I bet a good exhaust shop could do this for a lot less with after market cats.

I just dont understand this reply just to see if your cats are plug by drilling holes or torching holes

in the exhaust pipe before the cat now you have ruined the exhaust system by doing that and have to replace the pipe instead of just replacing the cat. Say the cat is not plugged now you have to fix what you did, if the cat is plugged now you have to replace the cat and the exhaust pipe. To me that not the way to do it to see if you have a plugged cat.

[Grumpy Bear]

 

8 Best Catalytic Converter Cleaners (2023 Guide) (mechanicbase.com)

 

Then figure out why it plugged. 

Edited November 11, 2023 by Grumpy Bear

[CamGTP]

Limp mode always throws a code, I would want to know what that code is before jumping into any repairs.

 

And you'd know if the cats were plugged if you just took a temp gun to the exhaust or if they started glowing red at night.

[mjm-1957]

If you suspect a clogged cat or restricted exhaust remove the front O2 sensors and road test.

[Kevin0311]

cheap scan tool (accutron) can watch the 4 o2 pre/post cat temps, my 14 needed cats oem setup was expensive took a chance on napa brand for less than half the cost has been fine for a year and few thousand miles. My codes were cat related codes even swapped 4 new o2 sensors before replacing to tripple check. i tried a can of catclean didn't work. mine didn't clog for no reason had other issues making it run rich for long time with check engine light on that was ignored.

[Mshawn]

On 11/11/2023 at 2:04 PM, mjm-1957 said:

If you suspect a clogged cat or restricted exhaust remove the front O2 sensors and road test.

After reading this post. Finally a correct step in the right direction in troubleshooting. You’re going to turn on the check engine lights and have to clear codes but if you remove the o2 and drive and it has a lot more power, yes the cats are plugged. I’m responding to this in the assumption that you do not have access to a quality scanner. Anyway from there you can decide what to do. I would call a few exhaust shops get a price on aftermarket converters.