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Discussion Starter #1
Hi all, i have had a bit of a search and i cant seem to find anything simalar.

I have a 95 Sierra
and when she warms up it blows blue smoke, but mainly when idling, taking off at the lights, and big time when backing off.

under load, its not too bad.

I asumed it was valve stem seals, so i did them, and still the same.

I have just done a compression test (as good as i can with the push in Supacheap compression tester) and both cold and hot, all cylinders come up to 150PSI

Number 4 spark plug was very oily and caked with crap, the other 3 were fine.

any sudgestions?

could i have a cracked head or intake port or something?

very anoying, because it runs fine otherwise.

any advice would be appreciated.

Regards Tony
 

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is it just blowing smoke or is it making a loud tapping noise as well. my first engine was doing both and it turned out to be that my con rod was warn and letting the piston go to far up and down end result was a blown up engine. if its just blowing smoke i would suggest the piston rings need replacing.
 

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Discussion Starter #3
No knocks, it runs fine, just blowing losts of smoke
but whats wierd is, that when driving under load, its doesn't blow that much smoke.

mainly when backing off.

could be oil rings?

and with the number 4 plug oiling up, i was thinking, maybe a crack in the head, letting oil into the inlet port?
 

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150 psi is marginal - but I have no idea how you arrived at that.

Re-do the compression test - this time do it properly - throttle wide open, engine warm, and both wet & dry - and let's see what the numbers look like.

The difference between the wet & dry numbers (if there is one) is what will indicate how worn the rings are - but oil smoke at idle, and on the "over-run" (what you describe as backing-off) - both high vacuum conditions - suggests valve seals.

What's the actual oil consumption like?

I rebuilt my 1.3 just over a year ago - very little smoke, but moderate consumption (a quart plus in between changes) and ridiculously low compression (just over 90 dry, 199 wet).
 

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Discussion Starter #5
Thanks for the advice, ill redo compression test tomorrow, wet and dry and post results.

Tony
 

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Discussion Starter #6
ok, here are the results of proper compression test as listed above (thanks fordem), just done now Throttle wide open.

Dry -
#1 - 195psi
#2 - 197psi
#3 - 196psi
#4 - 199psi

Wet -
#1 - 235psi
#2 - 230psi
#3 - 225psi (tested twice to check this figure)
#4 - 235psi

FYI, the previous owner has admitted, that the suzi has done a bit of beach work previously and it has overheated a couple of times.
 

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Discussion Starter #7
with these sort of results i'm guessing that, the rings and valve seats should be fine. Just going to remove the head and have it tested.

Ive already done the valve stem seals, so it really has to be a crack somewhere.
 

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Those results are unusally high - but yes, they would suggest the rings & valves to be sealing properly.
 
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