94 Chev 1/2 ton, 4.3 power problems, 200k miles


Old 09-08-04, 07:34 PM
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Join Date: Mar 2001
Posts: 23
94 Chev 1/2 ton, 4.3 power problems, 200k miles

My truck sometimes runs great, plenty of power during the first 20 minutes or so, and gradually seems to want to hold back. During the first 20 or so it is quiet and I have to be careful because it seems like a racehorse that wants to run. Then it gets louder, seems like it is struggling some. It downshifts on slight grades (where my 94 olds 3.8 just zips up those inclines with no problem). EGR is new and no codes. What are prime suspects?
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Old 09-09-04, 04:33 AM
Join Date: Dec 2001
Posts: 2,538
have the exhuast tested for a restriction most exhuast shops can do this they make a small hole in the exhuast and install guage to read back pressure
an exhuast system starting to get restricted generally runs better when the engine is cold and starts losing more power once the engine warms up.
other possibles would be fuel pump failing to provede good fuel supply to engine, fuel filter may be restricted also.
Old 09-15-04, 06:18 PM
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I think you can rule the fuel pump out. Engine revs increase on a downshift, which would exasperate a fuel pump problem. It would probably sputter and buck on a downshift if it were the fuel pump.
Old 09-15-04, 08:23 PM
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Join Date: Mar 2001
Posts: 23
Still haven't solved the problem but haven't had a chance to take it to have the exhaust checked. But, I have noticed with a couple of really cool mornings that it seemed to run fine the whole trip, but in the afternoon, with 90 plus degrees, the loss of power was evident. Does not seem to have any overheating at all, at least not according to the guage and any other obvious symptoms. I'm still puzzled.

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