RPSs erratic after driving for a half hour or so???

[mark241307]

Hello Friends, I am stumped on this one. I have a 2000 Nissan Frontier Crew- 5spd 3.3v6 4x4. Love this truck. I take great care of it. Has 152,000 miles on it. The problem I am having started just last week when I was driving for about a half hour. The RPMs started to go very erratic and the truck was not getting power when gas pedel depressed. In idle/neutral, everything seemed fine. As soon as I put the truck in gear, it would happen again, and the truck seemed like it was gonna stall. After getting it towed, I went thru the list, checked for vac leaks, changed fuel filter, spark plugs and wires, dist. cap and rotor, fuel pump relay. At 1st I thought it was a fuel issue because the pump wasnt turning on, the first few days I was working on it. After I changed the relay, the pump was fine. The guy at the shop down the street is also stumped, but says, he thinks its an ignition problem, most likely the distributer. I was reading about someone who had the same problem and they found it was the crank pos. sensor. If anyone can help me with this, I would appreciate it. Let me know if you need more info. I have never had the timing belt replaced, It is the next thing on the to-do list when I get the truck to stay running. Also the altanator is original.
Modified by mark241307 at 8:17 AM 2/6/2010

[RT22]

I must assume it is electronic tach, mechanical cannot work then go nuts it either works or dies. I bet the pickup unit or some part of the tach system is failing. need a schematic to see what all is in the loop. Money says it is electronics falling out with heat most likely if it takes a bit of time to go nuts. Or the pickup or some part is just starting to fail. Go to nissan website and see if any tech bulletins have been issued with the trouble and a fix.