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Discussion Starter #1
Hi gang.
I have a 1990 Sammi EFI 1.3L engine. Car has 55,000 miles.
I'm burning an excessive amount of oil. (Quart per 500 miles)
I did a compression test and these are the results:

Engine = warm
CYL DRY WET
1. 180 200
2. 180 200
3. 180 198
4. 180 210

How can I tell if the problem is rings or valves or valve seals ??

Please advise. Thanks in advance.

Doc.
 

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First - some mechanics will tell you that a quart every 500 miles is too much oil to be the valve seals, therefore it must be the rings.

Having pointed that out - as a general rule, the determination on worn rings/cylinder walls is made by evaluating the wet & dry compression test numbers - your numbers appear to be good, suggesting the rings are not excessively worn, which would go 'hand-in-hand' with the low mileage.

What I need to make clear, is that the compression numbers are affected by the sealing of the compression rings and have little to do with the oil rings, whose job is to scrape the oil off of the cylinder walls, so in a situation like yours, where the numbers look good, it's hard to determine whether it's a ring or a valve seal issue.

On the surface it does not appear to be a ring problem, but, it is entirely possible for the compression rings to be in good condition whilst the oil rings are stuck, worn or broken, in which case they will allow oil into the chamber.

Does the engine smoke, and if so, when is the smoke most visible?

Engines that smoke at high rpms typically have worn rings/bores, engines that smoke just after start up and when pulling away from a stop, are more likely to have leaking valve seals.
 

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Compression numbers look good.
I wouldn't suspect any issue there.
How do the plugs look?
My guess is they look fine.

PCV been changed?

Low miles !!!!

Don

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Discussion Starter #4
Thanks guys.
I am going to do a leak down test Tuesday and see if I can get some more diagnostic answers. I did change the timing belt and it seemed the the new belt felt a lot tighter tan the old one. The old belt had very good looking notches but that age cracks in the belt backing. I am positive that the belt is installed correctly, but the excessive tension make me wonder if the belt is correct size. All alignment points were correct and the crank through (two revolutions of the crank by hand) seemed OK. Any thoughts on that point ?

Doc.
 

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I can help but wonder at the sequence of tests and the questions that are being asked - it's as if you have access to test equipment but lack the knowledge & experience to understand what the tests do, how to interpret the results and what they can reveal.

What exactly do you expect to learn from a leak down test at this point?

Leak down tests, like compression tests, are a way to evaluate the condition of an engine, specifically with regards to the rings and valves and how they are sealing, most people do a compression test in preference to a leakdown test because it's easier - leak down tests require the test set along with a source of compressed air, the compression tests require just the test set - both tests will reveal that that there is a sealing problem, and to some extent where the problem lies.

What a leak down test will do for you is provide a tiny bit more information as to where the sealing problem might lie - when a compression test will suggest leaking valves or head gasket, a leak down test might help pin it down to which valve - which in my mind doesn't make a lot of difference because once you've isolated it to valves, the head is coming off and a complete valve job done.

Given the compression test numbers you've already posted, I would not expect a leak down test to provide any more insight as to how oil is getting into the combustion chambers and being burned.
 

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Discussion Starter #7
Thanks Fordem.
I am very confused about the results of my compression test.
What is the best way to determine if I have valve (or valve seals) or if I have an oil ring problem ?
It seems as though the whitest/blue smoke happens after the engine has been running for about 5 minutes. When I idle, the smoke is very light. When I accelerate, the smoke comes after my foot is off the pedal. So I have smoke all the time.
I had hoped the leak down test would give me a little more info to pass on to those with more knowledge than myself.
I plan to do this on Tuesday, but if you can pinpoint the problem to valves or rings, let me know.
If valves, I will have the head rebuilt.
If rings, I don't have a plan as yet.
Again, thanks for your help.

Doc.
 

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Your compression specs are in order as provided.

Separating ring / piston from valve seating leakage is easy enough to determine. All of your cylinder pressures are within spec, thus there is no indication of sever wear in that area.

Piston sealing verses valve sealing is where the "wet" test comes into play. The added oil tends to elevate numbers when the rings and cylinder bores are then oiled. Your figures improve some in the wet test which is common.

Worn valve stem guides and seals can not be evaluated via a cylinder pressure test. There you need visual and dimensional valve stem area checking at the Machine Shop level, unless tool and knowledgeable at home to comply.

Given your low mileage, vehicle age (but lacking service maintenance history) I would suspect many short trips and inadequate oil change periodicity. That would lead to moisture / sludge build-up within the engine.

I would first use an engine cleaner additive and several oil / filter changes to better evaluate IF internal passage cleanliness is the issue. Blocked passages will flood the top end of the engine with oil that can permeate down via the valve guides. And sludge caked rings will leak oil by as well.

What weight oil are you using? 5W-30 should be the choice.

What is the engines internal cleanliness conditions as viewed via the open oil fill port? :huh:

Try the engine flush & clean / drive it technique first. You have nothing to lose and you may just ward off an expensive engine tear-down. ;)
 

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I had the same problem with my 89 Sidekick 1.3L with 60K miles. I had no visible smoke at idle but when off road, engine braking down steep hills in second gear there was quite a bit of blue smoke. When the throttle plate is closed and the engine RPM is high you have low intake manifold pressure (high vacuum) and oil is being sucked past the intake valve oil seals.
If you are handy, you can change the intake and exhaust seals with the engine in place. My seals were dried hard and cracked when I removed them.
Since I changed the seals there is no more visible smoke. I use Mobil 1 15W-50, it is hot here in the desert, and I use about 1 quart in 1K miles. 95% of my driving is off road, usually in 1st or 2nd gear and I am not sure how this affects the oil consumption.
Hope this helps.
 

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As I mentioned in my first response, in a situation like yours, where the compression numbers look good, it's hard to determine whether the oil consumption is the result of a ring or a valve seal issue.

Before I go further, there is a possible area of confusion that I want to make sure you understand clearly - you'll come across discussions that talk about valves leaking or not sealing properly, and that these will show up in a compression or leak down test - I need you to understand that this not the same thing as leaking valve seals - valve seals are rubber lip seals that sit on top of the valve guides and seal the gap between the valve guide and the valve stem to prevent oil from passing through.

Compression and leak down tests will give you an idea as to how well the compression rings and the valves are sealing, but there is no test that I know of that determine if your valve seals are leaking, and there is no test that can determine if the oil control rings are doing their job.

What this means is there is no way to definitively pin down the problem area, but based on your report of smoking all the time and the level of consumption (one quart every 500 miles), my guess would be that the rings are where the bulk of that oil is passing - please note that wording, I'm not ruling out leaking valve seals, it's just that from the sound of it, you're burning more oil than would be normal for an engine with worn rings.

Incidentally, there is a third way for oil to get into the combustion chambers and burn, via the PCV valve, but, this is not known to be a problem area with this engine, having said that - it's cheap and it won't hurt to change it.
 

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I had the same problem with my 89 Sidekick 1.3L with 60K miles.
I want to make sure that you recognize the symptoms are VERY different...

On the one hand ...

I had no visible smoke at idle but when off road, engine braking down steep hills in second gear there was quite a bit of blue smoke.
And on the other ...

It seems as though the whitest/blue smoke happens after the engine has been running for about 5 minutes. When I idle, the smoke is very light. When I accelerate, the smoke comes after my foot is off the pedal. So I have smoke all the time.
 

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I guess I interpreted his description of the problem a little different.

"When I idle, the smoke is very light"..... Closed throttle plate and low manifold pressure.

"the smoke comes after my foot is off of the pedal"......Closed throttle plate and low manifold pressure.

Both of these scenarios make me think the intake valve guide seals would be the probable cause.

If it also smokes under hard acceleration, stuck or broken rings could be part the problem.

I do agree to replace the PVC valve, it is inexpensive and will eliminate this part as the source.
 

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Discussion Starter #13
Guys.
Thanks for the help.
A little more insight for you. I have changed the PCV valve and I find no visible signs of oil residue in any of the vacuum lines.
I will try driving the car again and get more detailed information as to when I have smoke and when I don't have smoke.
The plugs are new (100 miles on them) and they look perfect. Nice color and no signs of oil contamination.
At times it seems I'm running rich, but that could be from removing the battery while working on other areas of the car and the ECU hasn't had a chance to catch up with the right AFR.
More to come soon.
Again, thanks for your help.

Doc.
 
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