Engine Performance problem
1989 Buick Riviera 6 cyl Front Wheel Drive Automatic 123000 miles
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I asked about this before, and was advised that the Throttle Position Sensor (TPS) was probably the problem. That made sense because the computer did give that trouble code. I changed the TPS and adjusted it so that the reading was .63V, which is in the range.

The car still idles really high. I took the Idle air control valve off and hooked it up to a new 9v battery to make it retract. It would not retract.

I put it all back together and tried it again. It still idles high. I then cut it off and turned it right back on before the engine stopped, and it idled fine (smoothly at 800 RPM). Then I turned it off, waited a minute, and started it again... back to square 1.

What do I do next? What do I check? The diagnostic scan still gives me a code 22 (TPS) even though I reset the computer. I'm stumped. Please help! Thanks.

Too fast an idle speed. If an engine without computerized idle speed control is idling too fast and refuses to come down to a normal idle speed despite your best efforts to back off the carburetor idle speed screw or air bypass adjustment screw (fuel injection), air is getting past the throttle somewhere. Common leak paths include the carburetor and throttle body gaskets, carburetor insulator spacers, intake manifold gaskets, and of course, any of the engine's vacuum fittings, hoses and accessories. It is even possible that leaky O-rings around the fuel injectors are allowing air to leak past the seals. Another overlooked item can be a worn throttle shaft and a defective idle speed speed control motor stuck in the extended (high idle speed) position