You're going about this all wrong. Three-wire camshaft position sensors and crankshaft position sensors can't be measured because there's all kinds of circuitry inside. Two-wire sensors can read anywhere from a few ohms to over 1,000 ohms. No two will ever read exactly the same, and they won't cause your symptoms. Throttle position sensors will all read differently, and they could vary widely in resistance and it wouldn't matter. The wiper picks a point where it measures the percentage of total voltage applied. That won't change even when the resistance value is different. Also, the value of a TPS can't change. Oxygen sensors develop a tiny voltage. There is nothing you can measure, and if you did, I wouldn't know what to expect.
These values that can be measured may be listed in the service manual for reference but even there they give a pretty wide range of typical values. If a sensor did somehow change in resistance in a way that would affect engine operation, the Engine Computer would detect it, turn on the Check Engine light, and set a related diagnostic fault code. When you do get a code you will find almost always there's a break in the wire, a corroded terminal, or a total break inside the sensor that creates an open circuit.
For learning about engine sensors I developed a worksheet that required my students to measure the resistance of some sensors and the voltages on the signal wires. That was only to understand how they work, not to do that when looking for the cause of running problems. In fact, mechanics rarely test sensors individually until other testing points to one being defective.
You're right to not want to throw a lot of random parts at the problem. The computer learns their values and constantly compares them to what it expects to see from other sensors under various operating conditions. Relearning new sensor values doesn't always occur the first time the ignition switch is turned on. Specific conditions may need to be met and until then the new sensor will generate different signal voltages than what the old one would have. The computer will respond to those different voltages thinking they're coming from the old sensor.
One of the biggest problems GM has is with unequal flow rates from the injectors. Chrysler buys their injectors from Bosch in flow-matched sets. GM grabs a handful out of a big bin of injectors and stuffs them in with no regard to matching the flow rate. After many miles of wear and varnish buildup that mismatch shows up as one or two cylinders running lean. The oxygen sensor detects that lean condition and the computer responds by commanding more fuel, but ALL the cylinders get more fuel.
You also have to look at the ignition system as the cause of random misfires. On '96 and newer models the Engine Computer will detect which cylinder is misfiring and set a related fault code. On older models you have to determine that yourself.
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Monday, April 1st, 2013 AT 6:48 AM