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2004 chevy trailblazer_lt
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218 Posts
Discussion Starter · #1 ·
I've always wondered what was up with the roughness in our engines. From about 2500 rpm to 4000 rpm, it gets inexcusably rough. But somehow, I guess from the cam switchover, at 4k it gets nice and smooth all the way to redline. Why can't it be smooth and wonderful all the time? :hissy: If this was some crumby older pushrod V6 I could understand. But we have a DOHC Inline 6! What gives? Sorry, this has just been bugging me for far too long, and I really want to know if there's anything that can be done about it. Thanks for listening! :)
 

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Western Canada Chapter
2003
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6,411 Posts
Something is wrong in there. This engine is as smooth as silk even before the tune. It only had a funny type of "power band" as it transitioned through the variable valve timing, but always smooth.

Clean the throttle body and use a good fuel system cleaner and see what happens :undecided Anybody else have an idea to toss in?
 

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2004 chevy trailblazer_lt
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218 Posts
Discussion Starter · #3 ·
I've run a bottle of Techron through it, it's been a little while though. A few months ago I did the Seafoam treatment. And I keep my throttle body pretty clean. I also run synthetic oil, but it had dino in it when I got it (72k), then I switched to Mobil 1, and now Amsoil, and it didn't make any difference. I'm not sure what it could be, but it drives me crazy. I'm worried it might be something with the cams, because like a light switch at 4k rpm it goes away. But I've had it tuned, which is supposed to lower the switchover point, and it did it at 4k before and after.
 
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