1989 NISSAN SE 2WD POOR GAS MILEAGE- VACCUM LINE DIAGRAM

  • Tiny
  • shimman
  • 1989 Nissan Truck
  • 6 CYL
  • 2WD
  • automatic
  • 127,000 miles

I have a 1989 Nissan pick SE. VG301 motor V6 2WD with 127,000 miles on it. I recently had to change the heads due to a timing issue which froze the valves up and I lost compression. Since the new heads have been on I have got poor poor gas mileage and heavy black soot in tailpipe, so thick its eaten a hole in the pipe. As driving I feel like a backpressure or surge when gas pedal is not depressed. I was unsure of vaccum lines and where to re attach them. Any suggestions as to what is causes the poor gas mileage and can anyone provide me with a detailed diagram of the vaccum system. Mainly the lines that go to the throttle body or intake?

Saturday, June 25th, 2011 AT 9:40 PM

4 Answers

  • Tiny
  • shimman
  • Member

Also, I am currently not running a thermostat. Could this play a role?

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Saturday, June 25th, 2011 AT 9:50 PM
  • Tiny
  • rasmataz
  • Member

No thermostat-engine coolant temperature sensor stays in open loop and will not go in closed loop meaning it will be running rich all the time.

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Saturday, June 25th, 2011 AT 10:31 PM
  • Tiny
  • KHLow2008
  • Expert
  • 41,976 posts

Was the timing belt installed correctly?

This is the on; ly vacuum diagram available to me. Sorry if it is fuzzy.

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Saturday, June 25th, 2011 AT 10:37 PM
  • Tiny
  • rasmataz
  • Member

Its readable-KHLow2008-Could be a valve timing problem as you stated-

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Saturday, June 25th, 2011 AT 10:51 PM

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