1994 Chevy Caprice lack of power and burn gas

1994 CHEVROLET CAPRICE
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WILLDEAL
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Engine Mechanical problem
1994 Chevy Caprice V8 Two Wheel Drive Automatic 140k miles

my 1994 chevy caprice 4.3 v.8 have lack of the power it used to have and burn a lot of gas, I had a complete tune-up( changed spark plugs and wires, cap rotor,oil,gas,air filters,pcv,throttle position sensor,temp sensor,gas regulator,egr valve,idle air control valve, trans filter. trans diagnostic it was fine.did a compression test, it was fine, check the injector they were fine, checked the fuel pressure that was fine, check the cats they were fine.cleaned the mass flow sensor, and cleaned the throttle body to intake)And put it on the diagnostic machine and no other codes showed up, but my car is the same from before I started. what im I missing whatelse can i do to get my car back running good like before? My name is william @ 7737193229 or [email protected]
Nov 16, 2009 at 12:27 AM
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1DODGE2
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Welcome, Thats a lot of work and parts already performed. Were any codes present at the beginning? Try this test, first disconnect the mass air flow sensor and test drive. If the engine performance improves dramatically this is the faulty part. Replace it, clear codes and test drive again. Let me know if this worked!
Nov 28, 2009 at 4:46 PM
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WILLDEAL
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1dodge2, thanks but when i disconnected the mass air flow sensor the car cut-off. what should i try next, please help me.
Dec 11, 2009 at 11:11 AM
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1DODGE2
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Have someone rev the engine in park to approximate 1800 rpms. Check exhaust flow at the tail pipe at idle and at the 1800 rpm. If there is a significant loss of exhaust flow, the catalytic convertor may be clogged. You can confirm this by loosening the bolts at the forward flange or by removing the oxygen sensor and test drive a short distance to see if the power returns. There is a diagnostic tool and procedure for checking back pressure. It consists of a vac/pressure type gauge that can be screwed into the oxygen sensor hole.
Dec 11, 2009 at 9:51 PM