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Loss of power at 45 - 55 mph

Loss of power at 45 - 55 mph

Postby rchavex [OP] » Jan 12 2012, 6:20am

Hello, this is my first time on this forum. I have an 03 silverado 4x4 5.3 with 150K miles. A month ago I noticed it loosing power when I hit 45 - 55mph. I can hear the exhaust coming and going. It runs fine above or below the 45 - 55 mark and the exhaust has a steady hum to it. The service light came a few weeks after. It threw up code #3387. Local autozone said it was a faulty fuel cap or an minor vacuum leak. I've checked vacuum lines and replace fuel cap. Didn't notice change. I am not sure if the two issues are related. Would this be the fuel pump going bad? The truck turns on fine and doesn't have any power issues.
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Re: Loss of power at 45 - 55 mph

Postby ASTE25 » Jan 12 2012, 1:34pm

That code does not sound like a good number. Does the truck lose power at a certain RPM range, or at any RPM at that speed? What do you mean you can hear the exhaust coming and going?
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Re: Loss of power at 45 - 55 mph

Postby rchavex [OP] » Jan 12 2012, 4:16pm

It's difficult to explain without sounding crazy. But here goes. When I hit the 45 -55 mph range or 2,000 - 2,500 range, the truck starts feeling slugish. I describe it almost like starting to go up a hill and you can feel the car loosing power and you have to hit the pedal to get more power. As far as the exhaust, normally i hear a steady vroooooooom as I am driving. When it hits that range, I can hear the truck sound going from a steady vrooooom to a vroom...vroooom....vrooom. Here is another unusual comparison. But imagine you are listening to the radio at a steady volume. Then you lower the sound slowly and raise it back to where it was. Then lower it, then raise it. Does that make sense or did I just make things more confusing?

You are correct about the code being wrong. This is the correct code number P0442.
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Re: Loss of power at 45 - 55 mph

Postby ASTE25 » Jan 12 2012, 9:39pm

As far as the code, I would say it is just that you did not tighten your gas cap good one time. I don't think it is part of your loss of power problem. It's hard to tell whay may be causing your loss of power by your description. Does it feel like you are having a misfire or like it may just not be getting enough fuel? It kind of sounds like you may have an exhaust obstruction as well. Without a better idea of what you are feeling, it will be hard to diagnose. If you can think of anything else let me know.
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Re: Loss of power at 45 - 55 mph

Postby rchavex [OP] » Jan 12 2012, 11:41pm

It has me puzzled too. It does almost feel like it's needs more fuel. Yet, it does not misfire. It idles fine and handles nicely despite the high mileage. If I think of anything else I will post it. Thanks for looking into this.
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Re: Loss of power at 45 - 55 mph

Postby ASTE25 » Jan 13 2012, 1:26am

The only thing I can think of to do that would be pretty easy is to check the fuel pressure.
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Re: Loss of power at 45 - 55 mph

Postby rchavex [OP] » Jan 13 2012, 2:27am

I'm going to try that over the weekend. Not sure if it makes any difference, but the rpm range is 1500 - 2000 not what i had posted initially.
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Re: Loss of power at 45 - 55 mph

Postby wheeler82 » Jan 13 2012, 2:32am

yep check your fuel pressure, but if its not that sounds like it could possiblly be a plugged convertor. Also don't forget the simple things...check air filter if you havn't allready. Not sure if that would make it do that at that specific rpm range but you never know!
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Re: Loss of power at 45 - 55 mph

Postby ASTE25 » Jan 13 2012, 2:39am

Well, it's a puzzle for sure. Let us know back after you check some things.
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Re: Loss of power at 45 - 55 mph

Postby rchavex [OP] » Jan 13 2012, 4:32pm

Will do. Thanks for your help. I'll keep you posted.
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