High RPM and a bad PCM(?)

[hellmet]

About ten days back while reversing my 2002 Nissan Sentra (Automatic) the entire car shook and shuddered really bad. When I put it in Neutral and then tried reverse it worked fine.A couple of days back, after returning home, I noticed that my car started revving around 2000rpm in idle (Neutral or Parking). I was very tired and left it for the day. The next day when I started it, it did the same thing. Now when I stepped on the gas pedal, the engine acted like it was dying. Nevertheless, I continued on my trip to the bank when the problem got worse and the car just stalled, and the Service Engine Light turned on. I switched off the ignition, and after a few seconds turned it on. Luckily it started, and I made my way to a car mechanic. Strangely, all was ok when the mech. test-drove it.

I was dropped at home, and the car was with the mech. for 2 days. He replaced the Idle Control Valve, and the TPS. He called me up today and said everything was fine and I could take the car. I went there, started the car, and went to a gas station. After filling up, I turn the engine on and the same story repeats. This time around, the car idles above 2000rpm, and is steady there. I couldn't even move the gear stick from idle. Everytime I moved the stick, the car would judder.

I leave the car with him again. He removes all the sensors and refits them and seals them. He takes it to the Nissan Dealer so he can program the computer to adjust to the new Sensors.The Nissan dealer says he is unable to feed instructions to the computer and tells the Mech. that the PCM needs replacement.I just want you guys to let me know if all these pieces of info. fit together. I've already spent a fortune on this and seriously can't afford more.Could it really be the PCM or could it be something else? I have a slightly loose negative terminal on the battery. Could it cause problems?Also let me know if buying a used PCM from Ebay or something would be a good idea.

[Q45tech]

Nothing like second hand info with someone between you and dealer. Without tools or spare parts to test. Good Luck.

Unfortunately what you can afford has little to do with the cost to correctly repair a vehicle.