This is a 2+2, not twin turbo, with 122k miles. A few months ago it started not quite making it to the next gear while accelerating. It's worse at higher speeds. It makes a vague rmmm and you can feel that it's not hitting the gear as the rpm gage suddenly goes very high. I back off the gas and gently back on again and it will catch on the 2nd or 3rd try.
Perhaps unrelated, I've had periodic charging issues and several batteries in the 7 years I've owned it. I just replaced a battery with one cell dead and the shifting problem is clearly better, but clearly still there.
I have, only on 2 occasions, smelled gas. Extraneous perhaps, but I just had the fuel filter replaced thinking it might be related to the shifting.
The last transmission flush was at 64k. Yikes. I'm told not to do that yet as I may end up getting some other service that includes it. It appears certainly overdue in any case.
At 103k, had the timing belt, seals, water pump, thermostat, belts, brakes done. I've kept up with oil changes.
How can I figure out what's actually causing the shifting problem? I'm scared to keep paying for things I don't need without fixing the problem and I know nothing about cars! (Except that 300ZX rocks!)
Majority of Foreign designed vehicles are fiited with ECT which is ( Electronic Controlled Transmission ) and a computer called TCM ( Transmission Control Module ) that communicates with the PCM (Powertrain Control Module ) main computer to operate the transmission electronically by processing signal inputs from sensors involved such as coolant temperature/vehicle speed/throttle position/brake signal and in return commands the assigned solenoid/s to provide Overdrive/lock-up/upshift/downshift.
I recommend that you have the sensors check as mentioned
Your charging system and battery must be fully operational so that the computer/s recieves the correct electrical pressure to function correctly.
Its like saying if you are made to have four legs and your missing one, then you won't be able to run as fast as before.