why my rpm is getting down when engine is hot?

1995 TOYOTA
50,000 MILES
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SHUVO6745
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my car is a SE vintage 110 model Toyota.when i drive for sometime and then if i start it again it took start but it does not shift from oil to cng .at the same time its rpm gets lower and it comes to 300 or 400 when i release the accelerator.
May 13, 2012 at 8:28 AM
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DRCRANKNWRENCH
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If your car is powered by CNG, you might have a pressure problem or injector problem. It gets worse when hot because the car is leaned out by the Idle air Control valve andthe inadequate pressure will not keeep the CNG running without the help of petrol. You need to check your injectors and CNG fuel management delivery system.
May 13, 2012 at 8:35 AM
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SHUVO6745
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the same problem occurs in fuel as well.when i drive for 10-15mins after that if i stop in signal or anywhere its rpm gets down to 400.but in speed it doesn't give trouble.
May 13, 2012 at 9:15 AM
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DRCRANKNWRENCH
  • ✓ASE Certified Mechanic
  • 3,380 POSTS
  • ASE Certified Mechanic
Sounds like a fuel pressure regulator problem.
May 13, 2012 at 10:24 AM
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