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Old 06-01-2010, 10:49 PM   #1
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Compression test ...

I just did a dry compression test and the results are:

1. 165
2. 175
3. 175
4. 175
5. 170
6. 175

It seems to be ok (about 6% variance).

But what I have seen is that the normal range should be between 120 - 150 psi. What can cause my numbers to go up especially an engine with 165K+ miles on it?

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Old 06-01-2010, 11:01 PM   #2
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If they are that high I am betting you have a bad gauge.

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Old 06-01-2010, 11:04 PM   #3
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I just bought that thing for 40 bucks
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Old 06-01-2010, 11:31 PM   #4
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These are my spark plugs (6,5,4,3,2,1)
Attachment 19856

They have got about 200 miles on them and already look bad. I have misfire in cylinder#1. Already replaced the distributor, rotor, wires.

What should I check next? Please help!
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Old 06-02-2010, 01:31 AM   #5
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I'll bet you kept cranking and cranking until you got to the maximum, that's why they are higher than you expected.

Warm engine to operating temp.
Block the throttle all the way open.
Remove ALL the plugs.
Spin it so the gauge gets the same number of pulses on each cylinder. Usually 3 or 4, not more.
Then you'll have an accurate as possible set of readings.

What do you see in the picture that shows they are bad?

If anything, they look a little lean to me - too clean.
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Old 06-02-2010, 02:13 AM   #6
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Quote:
Originally Posted by rrich View Post
If anything, they look a little lean to me - too clean.
If they were bad they'd be toast.
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Old 06-02-2010, 12:14 PM   #7
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Quote:
Originally Posted by rrich View Post
I'll bet you kept cranking and cranking until you got to the maximum, that's why they are higher than you expected.

Warm engine to operating temp.
Block the throttle all the way open.
Remove ALL the plugs.
Spin it so the gauge gets the same number of pulses on each cylinder. Usually 3 or 4, not more.
Then you'll have an accurate as possible set of readings.

What do you see in the picture that shows they are bad?

If anything, they look a little lean to me - too clean.
You are right rrich! I didn't go by the pulses, I went by 5 seconds each. I will do the test again with your instructions and see what it comes out to be.

On the plugs, I am not sure what a bad one looks like (now I have an idea). I was little concerned about the deposits on the top of the plugs but I guess that is normal.

Since you mentioned they look little lean ... should I check the fuel pressure or some other sensor??
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Old 06-02-2010, 03:45 PM   #8
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No - let the O2 sensors do their job.

Did you swap plugs because you had issues, or was it just regular maintenance?

If it's not broken, don't fix it!
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Old 06-02-2010, 03:49 PM   #9
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I swapped them because I got misfire in cylinder # 1. It seemed to cure the problem until after about 200 miles it came back again.

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