1989 Chevy Truck lack of power

1989 CHEVROLET TRUCK
280,000 MILES • V8 • 4WD • AUTOMATIC
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PLY48
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I have an old body style 89 k3500. I hear a loud air sound coming out of the throttle body around the IAC. I've changed out the injectors, pressure reg. , IAC, o2 sensor, ERG, ERG sensor. The engine idles up and down and when you give it gas it lack power. Engine has been rebuilt 2 years ago and has ran great until 3 months ago. It has good fuel pressure. I'm baffeled to what it could be. I put in a super chip a year ago and it ran good.
Mar 30, 2008 at 11:24 AM
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2CARPRO JACK
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Any check engine light? Could be a cat converter that is melting down, Try loosening the exhaust before the cat/cats to let the gasses out, drive it to see if it has power again
Mar 31, 2008 at 7:24 AM
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PLY48
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I have no check engine light and the cat is removed.
Mar 31, 2008 at 6:08 PM
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2CARPRO JACK
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Try spraying around the TBI with carb cleaner, you may have a vacuum leak that is leaning out the mixture. Those TBI's sucked the throttle body gasket right around where you are describing
Apr 1, 2008 at 7:43 AM
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PLY48
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i sprayed carb cleaner around tbi and got nothing. i hear a loud vaccum sound around the iac inside the throttle body. i've changed the iac and still the same thing. idle goes up and down. whats next? greg
Apr 19, 2008 at 11:24 PM
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2CARPRO JACK
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There should be a little whistling sound out of the TBI, that is normal.Makes me wonder if it has an internal vacuum leak. That truck has a TH400 trans?, is the vacuum modulator good? (looking for possible vacuum leaks). What is the exact fuel pressure? should be 9-13 lbs with good volume as well
Apr 20, 2008 at 7:38 AM
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PLY48
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yes it has a th400 and the modulator is ok. I see that the iac goes in and out. this whisltling sound is to loud. the fuel pressure is @12lbs.
Apr 28, 2008 at 6:51 PM
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2CARPRO JACK
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Might want to remove the TBI just to see if it sucked the gasket internally.When was the last tune up? If you have a timing light, use it to see if the timing is advancing when throttle is applied
Apr 29, 2008 at 7:20 AM
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PLY48
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I changed the throttle body gasket and it was entact. I'll check the timing. It was tuned up about 6-8 months ago.
Apr 29, 2008 at 6:40 PM
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PLY48
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checked the timing and it is good. Whats next? Greg
May 13, 2008 at 9:48 PM
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2CARPRO JACK
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Take it to a shop with the ability to put it on a scanner and watch the sensors while driving it
May 14, 2008 at 7:36 AM
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PEAR69
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Make sure all the vaccume lines are hooked up to the TB -- if so -- then it may be a worn out throttle body shaft. Non-repairable -- Make sure there are no internal leaks inside of the TB -- If all checks out replace the throttle body ( TB ).
May 19, 2008 at 4:17 AM