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Q: 07 Xterra, starts and runs fine mechanically, no codes thrown, only idles? on 2007 Nissan Xterra

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Fuses and relays are good, no chk engine or codes thrown? but it will not accelerate at all. TPS, ECM or ______? not sure where to look or what to look at? Starts, after 1-2 seconds it drops the dash instrumentation (guages etc all fall to bottom) and it will not accelerate? ANy help appreciated.
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It could be a lot of things hard to guess without being able to do some tests first hand. Air flow meters used to give problems but would set a lean code. Could the catalytic converter be plugged up? Dropping the exhaust at the manifold or front of cat and then revving the engine would prove or disprove this. I would attach a vacuum gauge to the engine manifold and see what intake manifold vacuum is should be approx 21 in HG. Lack of fuel pressure or delivery volume? A professional grade scan tool reads stored trouble codes, pending trouble codes, looks at live sensor data so you can look at a sensors performance and output signals without having to do intensive testing at each sensor, (cheaper scan tools have limited capabilities and may only read the trouble code stored). As with most things automotive it's best to check the basics first, check for vacuum leaks, fuel pressure and delivery volume. Verify engine mechanical integrity before looking for complex problems check that the basics are sound.
Thanks, I`m a marine(mercury) tech and have 20+yrs working on motorcycles, but have limited cheap access to Nissan diagnostic equipment. The engine is in tip top shape mechanically, I`m fairly anal with the preventative maintenance work. What is confusing to me is that it has no codes stored. It fires right up, Drops the dash instruments, and the rt front headlight, then sits there and idles, shifts into gear etc but no throttle response? tried swapping the relays on the IPDM as a hail mary, to no avail. Guess I`ll have to hook up with someone with the pro diagnostics and figure this thing out. Now I know how the guys with the high end supercharged, wasp-nest of wiring and sensors EVERYWHERE Mercs feel...without the computer, you really don`t know where to look. Thanks, I`ll keep after it.
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