Trouble Code

Have a trouble code with my 96 Lumina sedan, 3.1 MPFI engine, auto tranny, 145K miles. It reads out, as I remember, P0101 which is described as 'calculated mass airflow does not agree with actual'. Originally, the engine idled a little rough. Did a tuneup (wires, plugs), cleaned the throttle body and idle air motor, and ran some Tekron fuel cleaner, all to no avail. Now the P0101 trouble code shows up. The engine idles roughly, dropping 200 RPM or so intermittently. Rough idle was the only complaint until lately the engine has also been rough above idle, stumbling on acceleration and noticeably rough into the 2500/3000 RPM range.

Since the mass airflow calculations involve input from many different sensors, am I left to start troubleshooting/checking each sensor one by one looking for abnormal or out-of-range readings? I'm a home mechanic, have digital voltmeters, and a workbench/electronic oscilloscope (not an engine analyzer). I'm left wishing that a sensor would outright fail, so a specific trouble code would point me in the right direction.

Previously, 2 months ago, had a code for multiple engine misfire, and found a large grommet on top of the throttle body disintegrated/missing leaking gobs of air into the manifold. Fixed that and the engine ran fine until this. Also, 3 months ago had a mechanic swap out the tranny for a good used one.

Any insight would be appreciated. Thanks,

Rick

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