I HAVE REPLACED THE CARB SPARK PLUGS LEADS FUEL ...

  • Tiny
  • jeromecoskey
  • 2001 Toyota Tazz
  • 280,000 miles

I have replaced the carb, spark plugs, leads, fuel filter and adjusted the timing to 10deg. I am out of answers, could you tell me why the car still idles as if its throwing away spark? This only happens at low end idling and revs, at approx 2000rpm it seems smooth.

Monday, February 4th, 2013 AT 9:06 AM

10 Answers

  • Tiny
  • mhpautos
  • Expert
  • 29,860 posts

Check that the comps are ok, check that the float height in the carb is correct, check for vacuum leaks, cap and rotor is ok? Let me know what you find.

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Monday, February 4th, 2013 AT 9:13 AM
  • Tiny
  • jeromecoskey
  • Member

Thanks, what is meant by comps?

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Monday, February 4th, 2013 AT 9:14 AM
  • Tiny
  • mhpautos
  • Expert
  • 29,860 posts

Cylinder compressions.

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Monday, February 4th, 2013 AT 9:15 AM
  • Tiny
  • jeromecoskey
  • Member

Yes all good, I've also been asked if it could perhaps be a sticky valve, what is your take on that?

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Monday, February 4th, 2013 AT 9:17 AM
  • Tiny
  • mhpautos
  • Expert
  • 29,860 posts

Could be, a compression test would normally pick that up because if the valve was sticking and not closing fully the compression on that cylinder would be down.

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Monday, February 4th, 2013 AT 9:20 AM
  • Tiny
  • jeromecoskey
  • Member

Ok let me double check

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Monday, February 4th, 2013 AT 9:44 AM
  • Tiny
  • jeromecoskey
  • Member

Ok compression is 1000, 1000, 600, 800. Does this indicate gasket or rings. No smoke is being burned.

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Monday, February 4th, 2013 AT 11:10 AM
  • Tiny
  • mhpautos
  • Expert
  • 29,860 posts

The 600 is very low, this will be the problem, you need to do what is called a leak down test, this is where you have an adaptor that screws into the spark plug hole, and with that cyl at TDC you have low pressure compressed air pumped in, not to much or the piston will be forced down, then you listen in the exhaust and inlet for air hissing, if it is leaking you will hear it. Also you can do a wet comp test, this is when you add a small amount of oil into the cyl, just enough to seal the rings, then re test the comps, if they go up it will be rings in they stay about the same it will be valves.

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Monday, February 4th, 2013 AT 11:53 AM
  • Tiny
  • jeromecoskey
  • Member

Thank you, will do this asap and give feedback. Thank you for the prompt and accurate advice.

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Monday, February 4th, 2013 AT 11:58 AM
  • Tiny
  • mhpautos
  • Expert
  • 29,860 posts

Your welcome and thank you for the donation, good luck with this.

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Monday, February 4th, 2013 AT 12:00 PM

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