1999 Chevy Tahoe

Tiny
TINCUPMI
  • MEMBER
  • 1999 CHEVROLET TAHOE
140,000 5.7. 4x4. I have a problem at acceleration. Very low power. When I hit the gas from a complete stop it acts like its starving for air or flooding? A good example of what is happening is, picture a manual transmission car starting out from a dead stop in 3rd gear. Once the tahoe gets to a certain RPM (2nd gear) it takes off like a raped ape. I mean it sits you right back in your seat. On the highway or in normal traffic, it has no hesitation or lack of power. Plenty of get up and go when passing. I have replaced the plugs, coil, Cat convertors, fuel filter, checked and cleaned EGR valve, checked air filter, and had to replace 1 O2 sensor because it was damaged while replacing the cats. NO TROUBLE CODES. I dont want to sink any more money into this and guessing what is wrong. It is an awsome looking and running vehicle other than this problem. It is also getting terrible fuel economy.
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Thursday, November 15th, 2007 AT 4:06 PM

5 Replies

Tiny
TINCUPMI
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I pulled the 2 fuses marked ECM under the hood for about 10 min. I was told this would help clear the driving habits of the previous owner. It made it worse I think.
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Thursday, November 15th, 2007 AT 4:14 PM
Tiny
PEAR69
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Ok lets start here. This is a very simple test. You need an assistant. Get an old rag like an old tee shirt or something like that. Go and drive around for about 15 or 20 minutes or so-- get the motor up to opperating temperature---Then stop but DO NOT TURN OFF THE MOTOR. Get the old rag and drape it over the exaust pipe. Observe how the rag is blowing away form tha tail pipe---have an assistant press the throttle just a little tiny bit to bring the rpms up to 1000 or 1100 that's all. If AT ANY MOMENT IN TIME the rag sucks into the exaust pipe you probably have a sticking exaust valve. Let me know the results of the rag test.

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Saturday, November 17th, 2007 AT 6:01 PM
Tiny
TINCUPMI
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Did the test. It doesnt suck in, just kind of goes back and forth (rag) slightly. When reved up at a higher rpm and let off, it did suck in though. Did the test on a new truck and it did the same thing. Is there any other way to test this? Is there a way to fix a sticking exhaust valve other than tearing apart the engine?
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Friday, November 30th, 2007 AT 12:33 PM
Tiny
PEAR69
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If the rag didn't suck in at a low rpm then it's most likely not a sticking exaust valve. There realy is no way to test this unless you have a trouble code leading you to a particular cylinder, or if you rip the heads off. It's probably not sticking anyway so lets move on. You may have a clogged injector or a sticking poppit in the injector. Unfortunatly there is no test for this but you can do this. Run the gas tank down to about 1/4 tank. Put some cheveron injector cleaner with techtron, in the big bottle, in the gas tank. Run that way until the gagus is almost empty. Then fill the tyank up half way and put another bottle in. Run that down and see what happens. Techtron is the chemical that the chevy dealers run through the fuel ststem at high presure to clean the injectors. Also, check or have the fuel pressure checked. It should be 66 or 60 psi. If not let me know. Check the plug wires. If you replace them put ac/delco wires in it. The aftermarket wires DO NOT, for some reason, work properly.I know these wires are expensive but they work. What type plugs did you use? Check ait cleaner area foe any leaks. How's the dist cap and rotor?
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Friday, November 30th, 2007 AT 6:04 PM
Tiny
PEAR69
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Sorry about the spelling in that last reply. Check air cleaner for any leaks. Besure to NOT use Bosch spark plugs ( lots of problems with Bosch). Tank and gauge are some of the other misspellings oops.
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Saturday, December 1st, 2007 AT 8:22 AM

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