I have an automatic GMC 99" Sierra 5.3L with about 150,000 miles on it. I am the original owner and have kept up with fluid changes. I have been noticing I been getting sluggish acceleration sometime shortly after startup. I understand that startup is the most intense on the engine until the fluids start flowing but I feel a couple of mins of warming up should be enough. I live next to a highway so when I leave the drive I need to get up to speed. Some times when I pull out onto the highway ill start to accelerate both the RPM's and Speed struggle. Its almost like it hits a point and then it starts accelerating normally. I don't feel like its a transmission issue because when I let the truck warmup longer it doesn't do it. Is this normal or is there something that could cause this? Thanks.
Well as a truck ages things don't work that well especially the fuel injection system because it needs extra fuel when it's cold but once it warms up it doesn't. So you might try the simple thing which would be changed the spark plugs and have the fuel injectors pressure cleaned. Perhaps cleaning can fix it. Although for my experience they often need replacing on those as they age with that kind of mileage
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