Possibly A Big Problem

Cdale2k · February 13, 2008

Ok, so my truck does this really strange thing. At low Rpm, runs great, but when i hit above 3800, or 4000 Rpm, the truck runs hella lean, and has no power at all. Now I have changed my front o2 sensors before the cat (only cause the old ones died after 180k miles), and added a different muffler to it to get the low end back pressure back. Now I have used a scan tool to watch my fuel trims and everything looks to be in spec. So I was wondering if you guys had any idea what could be causing this. Thanks in advanced

Linderman

99silverado1500 · February 13, 2008

Well it isnt a race car, I mean it will pick up at 4000-6000 to a good point, but a 5000 lb rolling wall doesnt accelerate like a corvette. What leads you to believe that its running lean at that RPM?

BurroWDMS · February 13, 2008

Ok, so my truck does this really strange thing. At low Rpm, runs great, but when i hit above 3800, or 4000 Rpm, the truck runs hella lean, and has no power at all. Now I have changed my front o2 sensors before the cat (only cause the old ones died after 180k miles), and added a different muffler to it to get the low end back pressure back. Now I have used a scan tool to watch my fuel trims and everything looks to be in spec. So I was wondering if you guys had any idea what could be causing this. Thanks in advanced
Linderman

Fuel filter changed lately?

67ChevyRedneck · February 13, 2008

Fuel filter, fuel pressure regulator, maybe fuel pump going out?

2004GMC1500CC · February 13, 2008

Ok, so my truck does this really strange thing. At low Rpm, runs great, but when i hit above 3800, or 4000 Rpm, the truck runs hella lean, and has no power at all. Now I have changed my front o2 sensors before the cat (only cause the old ones died after 180k miles), and added a different muffler to it to get the low end back pressure back. Now I have used a scan tool to watch my fuel trims and everything looks to be in spec. So I was wondering if you guys had any idea what could be causing this. Thanks in advanced
Linderman

Clogged cat?

Cdale2k · February 13, 2008

Yea, I know it shouldn't be anything like a corvette, its just that its no where near how it was a couple of weeks ago. And I haven't had my fuel filter changed recently. Probably 85,000 miles ago, if not longer. And how would i check my cats to see if they are clogged?

2000DV4.8 · February 13, 2008

Yea, I know it shouldn't be anything like a corvette, its just that its no where near how it was a couple of weeks ago. And I haven't had my fuel filter changed recently. Probably 85,000 miles ago, if not longer. And how would i check my cats to see if they are clogged?

I'd go ahead and change the fuel filter. It's cheap, easy, and you're past due.

And if your cat's are bad, your exhaust will smell BAD of rotten eggs.

Cdale2k · February 13, 2008

Well currently my exhuast does smell, but thats because i have a new cat back system. So its the paint and stuff like that. But running a straight pipe, and lean could have burned up the cat, couldn't it?

BurroWDMS · February 15, 2008

Yea, I know it shouldn't be anything like a corvette, its just that its no where near how it was a couple of weeks ago. And I haven't had my fuel filter changed recently. Probably 85,000 miles ago, if not longer. And how would i check my cats to see if they are clogged?

Oh my. 85000 miles? Run to the parts store (RUN) and change that fuel filter out. It's cheap and easy, and it's something that needs to be done A LOT more often than you are doing it.