1995 Chevrolet Blazer mileage 112,000. The problem is that the engine is so rich at idle that it lopes and stumbles. I replaced plugs (AC), wires (GM), cap, button, coil and fuel filter and performed all the basic checks before I took it in for diagnostics. The dealer said that the fuel injector was bad. I did not believe them so I took it to someone else; they told me the same thing. I replace the injector ($$$) this had no effect on the problem. It is not logging any trouble codes in the computer. I have now performed a compression test and all the cylinders are fairly even between 158 and 170. I also took the valve covers off and measured the lift at the rocker arms to see if there might be a cam lobe going down nothing out of the ordinary there. I checked the fuel pressure it has 62 lbs at start and 54 lbs running. I have swapped the crank position and the cam position sensors off my s-15, the idle air control and have also swapped the O2 sensors. I have checked anti-knock sensors 8400 ohms, I have tested the throttle position sensor and the engine coolant sensor all of which checkout with the book that I have. It has 17 inches of vacuum at idle so I don't think that it has a leak. Also the timing seems high 22 degrees BTC. Nothing that I have done so far has any effect on the problem. Any ideas?