Catalytic Converter Removal

I am about to have exhaust system replaced due to rust (already had frame replaced) and the shop says I have 2 CC in the system. They said they would take to CC's out of the exhaust if I wanted. Question is this, is the a good or bad move to do this ? I have read both pro and cons to this. Better mileage would be great for sure if that is a fact


Thanks

Maachuu aka Larry

 

Where do you reside?

If there is a tail pipe emissions check you would most assuredly fail.
Cats are a good thing, don’t get sucked into the “high flow” cat nonsense. ALL cats built today are of the high flow type, back when these monsters came out and weighed like 90 lbs, they were very restrictive.
You won’t benefit much if you remove them.

 

We don't have the inspection stations anymore in MS and then they didn't even check emissions

Thanks

 

If the truck is running good, there is no reason to remove it. Do you have a CEL light lit and how long has it been on?

It takes thousands of miles with the truck ruining in "open loop" to kill the cat(s).

Secondly, these trucks are very desirable. People from states with emission testing can not buy it if the cats are gone.

As for the exhaust being rusty, the complete exhaust from the cat back is only around $180 and they are easy to change in your own driveway.

If you remove the cats, the CEL will always be lit and the truck will use more gas since the engine is always running in "open loop".

"Open loop" is similar to running with the choke engaged on cars that had carburetors.

I'm really surprised that your mechanic suggested removing the cats.

 

The sensor after the cat reads the same as the one upstream, it can tell you if the cat is plugged as the gases change. It does not tell you the cat is good or bad in real time, just says “hey, burn is not within spec, check it out” which is one reason you never run race fuel in a cat equipped vehicle...

 

You betcha.

Because it's illegal, even in states with no inspections. It's a Federal law, and a shop that gets caught doing this for hire can get in big trouble.

I've seen troopers doing random roadside pull overs (of groups of vehicles, not individuals), checking tags, registrations, licenses, lighting system function and using mirrors to detect the presence of converters.

As far as the running of your truck, it will be louder. Yet poorer performance. Unless you can fool the ECU to think the cats are there and healthy. The move from OBDI to OBDII (with the post cat O2 sensors) in '96 made the removal of cats much more complicated.

 

According to exhaust shop, I have to have all the way from manifold back sue to the rust.


Thanks

 

When was the frame done? If recently the exhaust should have been done as part of the process, as they'd have to have had it apart to get the motor out.

 

Yes, that is correct, does not mean the cat is bad, it is telling you look here and perform some diagnostics. The code reader is a tool to be used to locate a trouble area, it is not the Bible of repair.

Scanning with a code reader and saying, the code says you need a MAF sensor without checking the systems or parts that surround the area and recommending a clean first is what TECHNICIANS do, a MECHANIC checks everything around and uses his head to determine the best action. Which is why I say, the cat can still be good even with a code, the wiring could be bad, the sensor, the plug, the pins in the ECU.....

 

Maybe I’m just a different kind of wrench, I trust nothing the computer tells me. You can have a cat bad code and have a bad sensor, you can also have a good cat, good sensor, but have a melted or broken wire and the code of bad cat comes up. Until cars carry things like passenger jets do, there are gonna be variables that need to be dealt with first.

Example, had a Nissan Juke read bad MPI for a wiper malfunction. It was not the MPI, it was the motor, which tested good both physically and live action diagnostic computer tests. There is a code for the motor, which did not hit.

 

@Running Man The P0420 code (cat malfunction) rarely means the cats are bad. Unless your truck has 200k+ on it. I've dealt with it on like 3 separate occasions in the past 3-4 years. First time it happened I took it to my mechanic to get the code read, he said the cats were bad and needed to be replaced and it would be really expensive. I thought hmmm, truck only has 130k that can't be. That was the moment I stopped taking my car to the mechanic. The most common problem is some sort of exhaust leak, usually very small holes that are hard to find, or ones that are more obvious (see below). The first time I dealt with it I was getting P0420 cause my catback rusted off (see picture below lol). Replaced that, code went away but all the readiness monitors wouldn't run. A week later cel came back on. This time it was bad rear O2 sensor. MY POINT being that P0420 can mean a lot of things, and a lot of times the other checks won't even run until the first problem is resolved (O2 sensor was also bad but I didn't get a code for that until the leak was fixed). This makes sense because the loop for testing O2 sensor signals couldn't even run properly because the proper amount of exhaust gas was not flowing by the rear sensor. The computers on these trucks and cars in general use discrete logic and inputs to turn on the CEL. Your brain can be smarter than the ECU and with enough thinking, and understanding of the system, you can make a better judgement than the ECU. This is why mechanics get paid the big bucks, or at least the good ones...

 

It's absolutely possible, but in the northeast at least most people just replace the cat thinking its bad from getting a P0420 which fixes the problem like 99% of the time. But in reality it is only fixing the rust and the cat wasn't bad. Could've gone with a much cheaper fix if you troubleshoot it for like an hour (check cat temperatures, look for holes, etc).

 

No we don’t, I used to get 40 per flag hour and never had to adjust my times or sit on a vehicle to make the time. Now I’m offered 18-20 per flag hour and have to work slow and adjust times if I go to fast.....which is why I’m done with it.

Labor prices went up, mechanics pay went down. The response is “ we have hundreds of techs wanting to work here” if you don’t like it we can just get another.

The best line from employers is, good reliable help is so hard to find......

You mean that all the 21 yr old master mechanics from UTI can’t actually fix anything?

Time to get another...

 

I will never go to a dealership or chain shop. I completely agree that how good a mechanic is, is gauged by years of experience and learning not formal education. However, that doesn't necessarily translate to pay and it is hard to differentiate between the two sometimes I guess. My family has used the same mechanic for a long time, he's on the more expensive side for a private shop. But he does good work, and will always explain stuff to you if you ask him. I've been trying to teach my family more and more about cars so they know what they're talking about and don't get ripped off by shops.

 

frame done back in March but no mention of exhaust at that time

 

Dealers are not all bad, you need them for the latest in software, warranty, and recalls.

You are right though most dealers care not bout the customer, they are too focused on the late 90’s early 2000’s way of operation......sales sales and more sales.... service and parts run the business not sales and “CSR” scores...

 

Well it didn't rust out between then and now.

You might consider seeing if they'd admit it should have been part of the process at the time.

Or if your shop is giving you accurate info. Manifold back is kinda unusual.

 

How does a stainless steel exhaust "rust out"?

 

Not all stainless steels are the same, the shit used on missiles and space craft is not the same as an exhaust or steak knives.

Exhaust also goes through thermocycles and that causes stainless to lose the stainless property over time, plus salt, road grime, rock impacts, animals, small children, and zombies that go under the truck cause dings and scrapes which allows the corrosion to set in.