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2001 Toyota Tazz Repair Question


Topics covered: Compression, Spark, Air pump.
Mileage: 280,000 miles.

Asked on February 4, 2013

Toyota Tazz Compression Problem

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.
Avatar Asked by jeromecoskey

Answer

Replied on 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.

Tiny Answered by mhpautos (expert)
26,913 answers provided
Replied on February 4, 2013

Thanks, what is meant by comps?

Tiny Response from jeromecoskey
1 question asked
Replied on February 4, 2013

cylinder compressions,

Tiny Answered by mhpautos (expert)
26,913 answers provided

Replied on February 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 Response from jeromecoskey
1 question asked
Replied on February 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.

Tiny Answered by mhpautos (expert)
26,913 answers provided
Replied on February 4, 2013

Ok let me double check

Tiny Response from jeromecoskey
1 question asked

Replied on February 4, 2013

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

Tiny Response from jeromecoskey
1 question asked
Replied on February 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.

Tiny Answered by mhpautos (expert)
26,913 answers provided
Replied on February 4, 2013

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

Tiny Response from jeromecoskey
1 question asked
Replied on February 4, 2013

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

Tiny Answered by mhpautos (expert)
26,913 answers provided