Losing Oil, Low Power, Rich Fuel?

[doubleKlutch]

My 2002 P5 is sick.
- Loses about 1/2 Quart of oil every day, or every 40 miles. (lots of oil going somewhere)
- Power wanes above 3500 rpm, you can feel very small waves of power/lack-of-power as it climbs through 4-5-6k rpm.
- Fuel Economy is fine, about 28-30 mpg
- Whisper of black smoke in the rearview above 4k rpm, but it's lost in the wind (Rich fuel?)
- No oil in coolant or coolant in oil (head gasket is good?)
- Minimal oil leak at rear main seal, no stains on driveway (not leaking)
- Minimal blowby, measured at the oil cap (rings are good?)
- Light unidentified occasional rattle, not heat shields (broken, clogged cat?)
- Occasional small blue smoke puff on startup, can only be seen from outside, behind the car
- Rare massive billow of blue cloud 1 out of 10 startups
- no smoke at idle, and none seen from rearview under normal driving conditions

The car seems to need valve seals, but I'm not sure what else. That's a lot of missing oil to not see coming out. Anybody seen this mix of symptoms on another Mazda? Could they all be related?

 

[tweety2300]

Valve seals won't cause it to lose 1/2 a quart a day. You have a massive leak somewhere

 

[doubleKlutch]

I've had a shop search for signs of a leak and they couldn't find one. It leaves no stains in the driveway.
I suppose it could be a pressure sensitive leak, and only leaks when driving... although I'd expect the mechanic to find evidence of that leak...

I should rev it up on ramps and see if it pees out any oil, but I've already started doing the valves. I'll finish them up since it smokes on startup.
I'll check the front main for signs of leaks behind the timing cover. Anything else I should look for while I'm in there?

 

[tweety2300]

Change pcv

 

[Fresco]

blue smoke during startup usually leans more towards bad or stuck piston rings from what I recall, maybe an mmo soak is something that can help with that, best way to see if in fact there is oil going into your cylinders is to check your spark plugs, and a leak down test or compression test can also help narrow down your problem

 

[doubleKlutch]

I took the timing cover off today and looked all around the motor for leaks, but there is nothing. It's dry as a bone.

Change pcv

Thanks. That was the first thing I checked and replaced. It was fine, but I replaced it with a new one anyway.

blue smoke during startup usually leans more towards bad or stuck piston rings from what I recall,

Rings can smoke when the engine is cold, because the rings leak before they expand with heat; But a short-duration plume of smoke right at start that dies within seconds is oil that has pooled overnight from above (valves) and remained in the cylinder, I think.
Can anybody confirm one way or the other on this?

maybe an mmo soak is something that can help with that, best way to see if in fact there is oil going into your cylinders is to check your spark plugs, and a leak down test or compression test can also help narrow down your problem

I did a 4-day, 3-night mmo soak, no change. I should have done a compression test by now, but I haven't. I'll do it the next time I'm at the shop, before I take the timing belt off.
Nice avatar, btw

The low power symptom could also come from bad rings. My buddy reminded me today that there are different ring types for different purposes and maybe the compression rings are good, while the oil rings have gone bad. But I don't really know much about ring combinations and distributions. I know that if the rings are indeed bad, I don't want to fix it. Too often new rings go in, and the cylinder is scored or the pistons are out of spec and it all burns anyway. Hopefully my compression test will be good.

 

[doubleKlutch]

Took a little while to get the test going. Had to reassemble the engine just a bit.
Compression test results:

# : dry / wet
1: 225 / 260
2: 230 / 260
3: 237 / 252
4: 223 / 265

This is my first compression test, but those look okay to me. Fairly consistent and above 200.
I find it odd that the best dry cylinder is the worst wet, and vice-versa. I'm not sure how to interpret that other than noise.

Any comments on how normal this test looks? Am I reading it right as a pass?
Any thoughts on how it effects my prognosis? Are oil control rings still in question? I feel like this shows that the rings are in pretty good shape. Not a big difference in wet/dry results.

For now, I'll continue on to the valve seals. It spat out a huge cloud of blue smoke in the shop when I warmed the engine for the compression test.

 

[tweety2300]

They seem a bit high, most are around 160-180

 

[doubleKlutch]

Yep, you're right. It's pretty high. Either my gauge is off, or I've got some carbon buildup. When I look through the spark holes, the piston heads do seem pretty dirty. Not sure why a 3 day mmo soak would leave so much buildup. Looks like I'm not one of those 'worked for me' mmo stories.

Likely, the carbon is coming from my oil consumption. The compression test does not imply bad rings, but the carbon could be messing up the readings.
Here's my plan:
- Verify the tester on another Vehicle
- Verify the compression with another tester
- Finish the valve seals
- Decarbonize the cylinders using water in the intake (can't do it now because the engine currently has no cooling system)
- Test compression again.

I read some stories about carbon buildup leading to a loss of power in the low end. Could it cause my loss of power at the top end?

 

[Fresco]

Have you tried seafoam for the carbon build up and a seafoam soak (just like the mmo soak) might help

 

[thuzil]

If you were leaking that much oil under pressure while driving the undercarriage would be covered as well as your rear bumper.

I would lean towards bad valves or cylinder rings. Try a leak down test to see where the problem might be.

Also try the compression rest with a me gauge as your numbers are way too high to be accurate for this car.

 

[doubleKlutch]

If you were leaking that much oil under pressure while driving the undercarriage would be covered as well as your rear bumper.

I would lean towards bad valves or cylinder rings. Try a leak down test to see where the problem might be.

Also try the compression rest with a me gauge as your numbers are way too high to be accurate for this car.

A "me gauge"? A new gauge? A new gauge is the plan, although I won't be able to look at it until Thurs.
I'll also borrow a leakdown tester and see what it says, although last time I used one (different vehicle), I got crazy results too... I see a pattern emerging.

And yes, I'd expect to see oil caked over everything if it were leaking on the highway. But it's the cleanest undercarriage in my fleet.

 

[doubleKlutch]

Have you tried seafoam for the carbon build up and a seafoam soak (just like the mmo soak) might help

I haven't tried seafoam yet, I only just discovered the carbon on my last visit. I should probably try it before using the water method. Although the old-school guys swear the water method is the most effective.
Here's some Indian dudes actually catching expelled carbon deposits from the exhaust after using water in the intake: https://www.youtube.com/watch?v=jWqN8pBHJhE

I'm turned off to the fix-it-in-a-bottle stuffs since my mmo and oil-thickener failures. There's also this stuff that has little particles in it that's supposed to fill in scratches in the cylinder wall. That sounds terrifying.

But when the car is on its feet again, after the valve job, I'll try both seafoam and the particle filler if needed. But I won't like it

 

[kamesama980]

Valve seals won't cause it to lose 1/2 a quart a day. You have a massive leak somewhere

My old 88 cressida cost over a quart in 10 miles through the valve stem seals after a curteous shop did an engine flush for me. Then again, when I got around to taking the head apart only 10 of the 12 valve stem seals were there to be removed...or at least 10 brittle clumps of viton). After doing JUST the valve stem seals (cam tower and valve cover gaskets had been done previously) oil consumption dropped to 1/2qt per 3k miles.

Yep, you're right. It's pretty high. Either my gauge is off, or I've got some carbon buildup. When I look through the spark holes, the piston heads do seem pretty dirty. Not sure why a 3 day mmo soak would leave so much buildup. Looks like I'm not one of those 'worked for me' mmo stories.

Likely, the carbon is coming from my oil consumption. The compression test does not imply bad rings, but the carbon could be messing up the readings.
Here's my plan:
- Verify the tester on another Vehicle
- Verify the compression with another tester
- Finish the valve seals
- Decarbonize the cylinders using water in the intake (can't do it now because the engine currently has no cooling system)
- Test compression again.

I read some stories about carbon buildup leading to a loss of power in the low end. Could it cause my loss of power at the top end?

Yes, yes, and yes. (VSS=oil consumption (though not necessarily only them), carbon buildup will lose power all over. Valve stem seals will cause buildup on both intake and exhaust valves as well as the pistons. I did em all on my S10 cuz they were CAKED.)

When doing the compression test, remember to remove ALL the spark plugs, disable fuel, and hold the throttle open for an accurate reading. My bike shows 30+ psi difference whether you hold the throttle open or not (~150 vs ~185). Cars aren't as bad since they have the whole intake to suck up but it still makes a difference. though you obviously don't have a problem with low readings I'm just sayin' cuz most people don't do it right.