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I have a 2004 trailblazer with a 4.2 engine it has a gremlin issue in the morning when you first drive it when it is cold it will al of sudden power out and run in surges for 20 second and then go back to normal, after it has warmed it doesn't do it anymore the rest of the day.Have changed fuel filter ,clean throttle body,replaced throttle pedal sensor.Have even had the dealer scan tool hooked up while it did it and showed nothing even check engine light doesn't come
 

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2004 gmc envoy_slt
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If there are no codes or check engine light on, I would suspect a transmission issue that does not come under the computer diagnostics.
 

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2007 chevy trailblazer_ls
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Thats a failure of the smog pump system. There is a pump on your left frame rail forward of the fuel tank, a control relay close to it, and there is a valve on the right side of your engine next to the exhaust manifold. Works only on cold start ups for the first thirty seconds or so. You’ll have to read up on it, most failures are with the relay or its fuse. Reduces emmissions on start up if I remember correctly. Hope this helpd.
TJ
 

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2002 chevy trailblazer_lt
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23 Posts
JOHN Deere makes sense, also check the PITA location and make sure the fuel pump wiring is good...too...I had a similar issue and it was the fuel pump starting to take a dive. Since then I did the VVT sensor and Cam Sensor, all the plugs to iridium and a new set of coils....all the bearings for the serp belt...boom she runs like a banshee I'm getting 17.4 ish city hwy driving per the computer....straight hwy my best has been 21.7 give or take if I'm doing 55 to 60....not sure if that mpg is good. It was always stuck at 18 when the TB was new. Good luck with find the issue, guy above makes sense too.
 

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2003 gmc envoy_sle
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70 Posts
Thats a failure of the smog pump system. There is a pump on your left frame rail forward of the fuel tank, a control relay close to it, and there is a valve on the right side of your engine next to the exhaust manifold. Works only on cold start ups for the first thirty seconds or so. You’ll have to read up on it, most failures are with the relay or its fuse. Reduces emmissions on start up if I remember correctly. Hope this helpd.
TJ
Agreed, as to be the likely cause. Sounds similar to my '01 S-10 Blazer. My smog pump was located in the position you'd expect if it was as typical, belt driven. But they switched to electric motors. Low, in front of the engine, down by the right front wheel, in the northern US? Electric? What genius didn't see electric motor failure stamped all over this. Mine ran ok for years, now it acts like yours.
 
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