Mechanics

TOYOTA TAZZ COMPRESSION PROBLEM

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.
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Jeromecoskey
February 4, 2013.



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.

Mhpautos
Feb 4, 2013.
Thanks, what is meant by comps?

Tiny
Jeromecoskey
Feb 4, 2013.
Cylinder compressions.

Mhpautos
Feb 4, 2013.
Yes all good, I've also been asked if it could perhaps be a sticky valve, what is your take on that?

Tiny
Jeromecoskey
Feb 4, 2013.
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.

Mhpautos
Feb 4, 2013.
Ok let me double check

Tiny
Jeromecoskey
Feb 4, 2013.
Ok compression is 1000, 1000, 600, 800. Does this indicate gasket or rings. No smoke is being burned.

Tiny
Jeromecoskey
Feb 4, 2013.
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.

Mhpautos
Feb 4, 2013.
Thank you, will do this asap and give feedback. Thank you for the prompt and accurate advice.
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Tiny
Jeromecoskey
Feb 4, 2013.
Your welcome and thank you for the donation, good luck with this.

Mhpautos
Feb 4, 2013.

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