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2003 chevy trailblazer_lt
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Discussion Starter · #1 ·
Hi I've got an 03 trailblazer with around 180k. I've begun noticing that i lose alot of speed when going up hills. I live in an area where i go over one on my way to work and no matter how much speed i build up (around 60-65) I'm down to 30-35 half way up the hill. Its not even a very large hill. I will note I had the cat completely replaced last year after a regular inspection suggested it needed to be replaced (it was really gunked up and probably never touched before). I did notice alot more power after having the cat replaced, I've also replaced the throttle body (about a year an half ago). Could this be an air intake issue or does anyone have any similar experience and possible solutions?
 

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2004 gmc envoy_slt
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Couple ways to address this to verify if cat is once again clogged. Have a backpressure test done on the exhaust or temporarily remove the upstream O2 sensor (located on exhaust manifold), and go up the hills you have to problem with. If there is an improvement in performance, you have a bad cat again. It is very unusual to have a cat go bad that quickly, so there maybe something going on with the engine.
What is the operating temperature as shown on the temp gauge? Should be around the 210 mark. If it is below that, you may have a stuck open thermostat. With engine running cooler than expected, the computer will feed more gas and this causes a rich mixture that will ruin the cat. Good luck.
 

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Are there any OBDII codes? Have you checked the fuel pump pressure?
 
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I understand. More of a case of here is another piece of information to rule this or that out.
 
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Discussion Starter · #7 ·
Thank you all for the information. I'll have the cat checked out by a different shop on monday and see what they say. I was also wondering if it may be a fuel issue perhaps the pumps wearing out or maybe even the filter is clogged (i had it replaced about a year ago so i'm not due to have it changed again for a while).
 

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Did you have the fuel filter changed or the fuel pump last year? If you had the fuel pump changed, was a Delphi or an ACDelco pump put in?
 

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OK. Thanks for the info. I tend to change my fuel filter every 2 years or 30,000 miles unless I get some "suspicious" gas.
 

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Discussion Starter · #12 ·
So i've had the pump and cat checked by two shops (i'm a car guy in training) both don't seem to think their the problem. I don't have any codes and outside of straight flooring the pedal i can only go maybe 40 mph up hills. Even with a nice fast head start i'll slowly lose momentum and drop down to 40-45 half way up. I'm still pretty stumped.
 

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Well, if you really want to rule out the fuel pump, get a fuel injection system pressure gauge, connect it to the fitting by the fuel filter, and see what your fuel pressure is. If you don't own a fuel injection system pressure gauge, you can "borrow" one through the tool loaner program at O'Reilly, Advance or Autozone. You leave a deposit on the tool and then when you return it, you get your deposit back.

FYI fuel pressure specification for your 2003 TrailBlazer is 50 - 57 psi. If the pressure is even 1 psi lower than 50 psi, you need to replace the pump because it is likely weak and dying. Trust me on this. Also, if you don't want to replace your fuel pump again in the near future, use only a Delphi or ACDelco pump. The cheap, no-name one's are known for their short lifetimes (as little as 10 days).
 
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