Im pretty sure both of my cataylitic converters are going out on my 2000 silverado, so im thinking about just cutting the cats off. ive heard you get better gas mileage without the cats anyways. the only other thing is ive got 4 02 sensors one in the back and one in the front of each cat. the front ones should be fine but what can i do to the rear ones to keep the check engine light off. Also is there anything else that will be affected without having the cats?

simple answer no. just replace them. you will not beable to keep the check engine light off, and it will probably end up getting worse fuel milage.

I'm curious why you think your 8 year old cats are going out. And the previous post is correct. Your MIL is never going to turn off without cats.

well all 4 02 sensors were bad for a long time, im getting terrible gas mileage, maybe 9.5 mpg, ive changed out all the regular mant. parts, like plugs, fuel filter, etc.. Also when i get on the gas at about 35 to 40 mph it feels like i have no power at all, it feels like im towing 10,000 lbs. and ive heard that clogged up cats can cause bad gas mileage and decreased engine power. idk ive looked into just about everything else and replacing the cats was what i came to. im fairly sure i have a vacuum leak around my intake manifold too but that wouldnt cause bad gas mileage and low power would it?

Yes you can cut them off. And you CAN get the light to turn off. Summit racing has 02 sims that plug in to the sensors and fools them. I took them off my 02 5.3 and it sounded like ass I noticed no MPG improvement or power. In my oppionion I wouldnt take the cats off on newer vehicles, if anything buy some magnaflow hi flow ones.

im fairly sure i have a vacuum leak around my intake manifold too but that wouldnt cause bad gas mileage and low power would it?

Ummm, no. A vacuum leak causes better gas mileage and power. :shaking:

Of course a vacuum leak at the intake causes negative issues.

So now the question is....why do you think your engine has a vac leak at the intake??

im thinking i have a vaccum leak beacause when its cold or has been sitting for a while it doesnt start very good. it will start right up but the second after it starts it almost dies.. then it starts to surge, you could say. the rpms go from 800 to almost dying.. four or five times (first 20 sec. its running) then its fine and wont do it anymore the rest of the day. im thinking its getting too much air causing the fuel mixture to be too lean. Also GM's are bad about leaky intake manifold gaskets i have heard.

Have you checked or replaced the fuel pressure regulator? My father had some starting issues on his 2000. Turned out to be caused by the fuel pressure regulator. Once replaced, the problems ceased.

yeah well ive thought about it maybe being a regulator or fuel pump.. but if i slightly open the butterfly (im talkin less then 1/32 of an inch probly) it will start up perfect everytime. so to me thats saying its getting fuel, idk if that would rule out the regulator or not though. but when the butterfly is opened a little the throttle position sensor will sense that therefore sending more fuel which makes the fuel mixture just rich enough to start fine. thats what im thinking, could be wrong though.

Your intake gaskets need replacing. Comon problem with 5.3 and 6.0 of those years. My friend just bought a 02 and had the same problems,replaced the gaskets and presto! idles good, alot better fuel mileage and no stalling.
don't be trashing those cats yet. If you do there worth about $75. each scrap.

Loosen the flanges on the exhaust manifolds and take it for a quick drive. If it runs better than it has in a while, the cats are probably clogged. I just went through this on my neighbor's Astro van.

Make sure you find out why they went bad. It could have been running rich with your bad O2 sensors, but I have never heard of 4 O2 sensors going bad all at once.

Then replace the cats.

Remove cats remove rear O2's, use HPtuners or such and remove MIL for rear O2's. The Dishes are done bitches!

The cats will not effect the mileage unless plugged up.

I am interested to hear your final solution. My dads truck 02 GMC is having the same start up issues, but he hasn't said any thing about loss of power. I replaced the fuel regulator and it did not help. It is extremely hard to start when cold, but does OK the rest of the time. I have heard the fuel pumps on these are junk. Could it be the pump has a hard time priming at first and then can keep up. My dad's only has 60K and he only drives it couple time a month. I sure would like to get it fixed.

well all 4 02 sensors were bad for a long time, im getting terrible gas mileage, maybe 9.5 mpg, ive changed out all the regular mant. parts, like plugs, fuel filter, etc.. Also when i get on the gas at about 35 to 40 mph it feels like i have no power at all, it feels like im towing 10,000 lbs. and ive heard that clogged up cats can cause bad gas mileage and decreased engine power. idk ive looked into just about everything else and replacing the cats was what i came to. im fairly sure i have a vacuum leak around my intake manifold too but that wouldnt cause bad gas mileage and low power would it?

well the old skool... way to check if your jive is clogged is to unbolt the exhaust and drive it and see if there is a difference.

im thinking i have a vaccum leak beacause when its cold or has been sitting for a while it doesnt start very good. it will start right up but the second after it starts it almost dies.. then it starts to surge, you could say. the rpms go from 800 to almost dying.. four or five times (first 20 sec. its running) then its fine and wont do it anymore the rest of the day. im thinking its getting too much air causing the fuel mixture to be too lean. Also GM's are bad about leaky intake manifold gaskets i have heard.

take a spray bottle or even carb cleaner and spray around your intake till your jive boggs or ya what ever.

take a spray bottle or even carb cleaner and spray around your intake till your jive boggs or ya what ever.

I prefer the method w/ a propane torch. Take a torch, open the valve, do NOT light, run it along all vacuum lines/intaks gaskets. The idle will run high when you find your leak due to burning the propane.:D

[QUOTE=hperiman;8034149]I am interested to hear your final solution. QUOTE]

i will be sure to let you know as soon as i get time to fix it. hopefully this weekend will be nice and i can replace my intake gaskets if i find thats where the leak is. its been raining just about all week so i havent been able to even look at anything really. then if ive still got problems ill try loosening the flanges on my exhaust manifold like Mark was saying and see what happens.