97 C2500 5.7 cuts out/loses power driving

[aaronb]

So you removed your cats? What did you do about the post cat o2 sensors. Did you have the truck tuned to eliminate them? If not, that's going to be part of your issue. The truck will run like ****.

 

[mutanay]

So you removed your cats? What did you do about the post cat o2 sensors. Did you have the truck tuned to eliminate them? If not, that's going to be part of your issue. The truck will run like ****.

Yeah found that out today. i did not get a tune. I wasn't aware of that when the guy told me i did not need to do anything once the cats were removed. Im thinking of just putting back the cats and screw the tune. It was indeed the O2 sensors

 

[df2x4]

So you removed your cats? What did you do about the post cat o2 sensors. Did you have the truck tuned to eliminate them? If not, that's going to be part of your issue. The truck will run like ****.

I've always been under the impression that the post-cat O2 sensors on the Vortec trucks are just there to see if the cats are working, and that the pre-cat sensors handle all the air/fuel stuff. Is that not the case?

My red truck still has cats, and I had a post-cat O2 sensor die in it once. Cats were fine, sensor just died for whatever reason. I drove it around for a week or so before I got it replaced and I never noticed any loss of power or anything strange at all, just the check engine light.

 

[GarrettGmc]

Makes me wonder if previous owner messed up something. I was told he had check engine light an replaced the o2 but forgot to ask before or after the cat. But still going to check fuel pump and filter.

 

[aaronb]

I've always been under the impression that the post-cat O2 sensors on the Vortec trucks are just there to see if the cats are working, and that the pre-cat sensors handle all the air/fuel stuff. Is that not the case?

My red truck still has cats, and I had a post-cat O2 sensor die in it once. Cats were fine, sensor just died for whatever reason. I drove it around for a week or so before I got it replaced and I never noticed any loss of power or anything strange at all, just the check engine light.

I gutted my cat a couple years ago to see if it was clogged up, after gutting.
My truck ran like crap, it ran rich, stumbled and would backfire getting into the throttle. Didn't tune out the post o2 sensor. The post cat sensor threw a code shortly after gutting the cat. I replaced the cat and the post o2 sensor and no more issues.

 

[mutanay]

I gutted my cat a couple years ago to see if it was clogged up, after gutting.
My truck ran like crap, it ran rich, stumbled and would backfire getting into the throttle. Didn't tune out the post o2 sensor. The post cat sensor threw a code shortly after gutting the cat. I replaced the cat and the post o2 sensor and no more issues.

Sounds like what I am about to do. If i can get my truck running like those 10 minutes after the tune up, then I will be more than happy. Who needs a loud obnoxious truck anyway. I am cool putting the cats back in and the o2 sensor.

 

[str8fan7]

my 94 5.7 didnthe same thing and it ended up being the ignition control module under the rotor. after i replaced that i have not had anymore issues...