how my small issue turned to big one

[mrQQ]

ok, so I have a 2007 MS6 with 40k miles on the clock.

DP, TMIC, TIP and CAI. Custom Tune.

Lately I've been getting damn rich readings, smells, rough idle and so on. Fuck it I said, and took it to the shop. Been whining on the forums too much, suspecting o2 sensors and so on.

So the story is like this..

188-145-130-175

these aren't lotto numbers..

leak-down showed air escaping through valve cover.

sooooo.... what's next..

[btstarcher]

New valvecover gasket? But those numbers look like a bad head gasket; what does your coolant look like?

Also, can you show me a log that displays your AFR, LTFT, and STFT? Not WOT, just driving, give it a little gas and let off, etc.

[mrQQ]

if it were head gasket it would leak through that, now it leaks through valve cover went in leak-down test.

as for log, the car is apart now, but basicly it's really rich in all the ranges, -16 at idle.

[MazdaBoy2.3]

No expert but I think it could be a head gasket as well. Air/coolant/oil doesn't need to leak outside of the engine for the head gasket to be blown.

[btstarcher]

That's not your AFR; that's your LTFT. I need to see what your O2 sensor is actually reading. Sometimes it's obvious that something is wrong. This won't fix your compression issue, but you might have more than one problem.

[mrQQ]

close loop afr always read 14,69 or around that.

edit: it could be head gasket, but i dont think i have any loss of coolant/oil..

[btstarcher]

So then you're meeting your targets? When my O2 sensor took a shit it was stuck at around 29, which is why my LTFT was increasingly negative. Wait for an expert to chime in, but from what I remember when 2 adjacent cylinders have low compression it usually indicates a problem with the head gasket.

[TiGraySpeed6]

compression numbers do lean towards head gasket. If it was truly an issue there would be supporting evidence- milky oil, white shit on oil fill cap, smoke from exhaust & mysterious loss of coolant, etc. Any of these, or a combination of them.

leak down test seems to be indicating a rings, however you've not provided any details beyond air loss- Which cylinders presented the symptom? 3? 2 & 3?

Rich readings can be triggered by something as simple as a boost leak resulting in loss of metered air.

Generically I'd approach these with a divide & conquer strategy. In this case I'd start with the low compression issue as that's more important than the rest. Define if it's rings or HG, then what you want to do. The Manual will tell you that as low as 125 is acceptable, but the variance between cylinders is, I think, too great to ignore.

But, these are the ramblings of just another guy. The real mechanics will be along soon.

[mrQQ]

Leak down was very small (i dont have any real numbers yet) on 1, 2 and 4, and was huge on 3, venting almost as fast as pressurising. Going out of valve cover breather.

No oil or coolant loss. Smoke, but I was attributing it to turbo. But the intake/tmic was clean, so perhaps it wasn't turbo after all, perhaps was rich fumes? No idea.

Oil and coolant seem to be clean.

Frankly, I have no clue what could have caused this. And not sure what to do further to make sure what it is exactly..

btw, could you tag some of the experts please, i'm not really very familiar around here..

[TiGraySpeed6]

To me, and again I'm not the mechanical pro, it sounds like rings or lands in 3, which is a common(ish) wear area.

IIRC, Intake or exhaust valve issues are usually found in leak down by losing the pressure to intake or exhaust mani's, rings are seen to vent to CC, then travel up through the TC area into the valve cover as the path of least resistance.

Smokey turbo from oil or the common K04 bad seals has a distinctly burnt oil smell. Coolant smells much different than burnt oil, sounds silly but it smells like coolant. You'd know the difference, and you'd be seeing the resultant lower coolant levels as it was lost.

[Deldran]

Originally Posted by mrQQ Leak down was very small (i dont have any real numbers yet) on 1, 2 and 4, and was huge on 3, venting almost as fast as pressurising. Going out of valve cover breather. No oil or coolant loss. Smoke, but I was attributing it to turbo. But the intake/tmic was clean, so perhaps it wasn't turbo after all, perhaps was rich fumes? No idea. Oil and coolant seem to be clean. Frankly, I have no clue what could have caused this. And not sure what to do further to make sure what it is exactly.. btw, could you tag some of the experts please, i'm not really very familiar around here..

I would agree, if you know someone with a scope i would get it in cylindar 3. Maybe u can see a ringland issue with it.

[TiGraySpeed6]

goodness, can't swing a dead cat in this place without hitting a respectable mechanic.

I gotta go do actual work stuff, but off the top of my head- @Dano; @phate; @BlueStreak;

There are so many more

[mrQQ]

just for the worst - IF i need to replace the rings.....

a) can you just replace the rings?
b) can those be used ones (don't shoot me, i know that a normal method is DO IT ALL, but...)
c) what else needs to be done?

just trying to gather some knowledge.......

[TiGraySpeed6]

Start by searching up some info on Drop-In builds.

It worked a treat for dougefresh_, but Dano's was, well, let's just say it became a bit more involved. So, drop in is a possibility, but only if the stars line up and everything goes your way.

[mrQQ]

thanks, found some threads except dougfresh_'s

otherwise, what is the proper way to do it?

[Deldran]

Originally Posted by mrQQ just for the worst - IF i need to replace the rings..... a) can you just replace the rings? b) can those be used ones (don't shoot me, i know that a normal method is DO IT ALL, but...) c) what else needs to be done? just trying to gather some knowledge.......

No u cant use used rings.
It will be an extensive fix. Honestly with the questions you just asked i would recommend having a shop do it for you.

It a lot of work, and if you want it done right you really need to pull the motor check all the specs and such, if the rings some how put a deep enough gouge in your cylinder wall you might need a new block. that would be worse case though

Originally Posted by mrQQ thanks, found some threads except dougfresh_'s otherwise, what is the proper way to do it?

If you plan on keeping the car and you can spend the money.
Yank the motor out, take it to a shop have it machined and go forged. wont be cheap though

[mrQQ]

I'm not even planning to do it myself! I just want to visualize what it involves.

[BlueStreak]

Originally Posted by mrQQ just for the worst - IF i need to replace the rings..... a) can you just replace the rings? b) can those be used ones (don't shoot me, i know that a normal method is DO IT ALL, but...) c) what else needs to be done? just trying to gather some knowledge.......

I suspect the ringlands. I have yet to see someone with low compression have only the rings be at fault.

Chances are the bore isn't scuffed or damaged so a drop in replacement with an OEM unit may be possible if you're on a tight tight budget; another option is a drop in forged build on all cylinders. Just need to ensure the bore is within spec w.r.t roundness.

[mrQQ]

ok, side question:

could it be that I'm having two (or more) different issues at the same time?

the reason i started digging was that I had some exhaust smoke (it wasn't really blue, it was pretty wite), some smells, bad mpg and very very rich trims (-16 at idle and higher).

at first I suspected the WB o2. Found no leaks, neither intake nor exhaust, plugs were black, o2 were pretty poort looking, and the compression test returned the terrible result.

Can the bad compression in #2 and #3 be the root cause of all the symptoms? Or let me rephrase: is it possible, that i have worn rings/leaking gasket, but it is NOT the cause of the above symptoms? Since the manufacturer rating is at least 125, it still is in it, so it should drive pretty normally?

So perhaps for now I can just try to replace the wb o2 and see how that works out, while getting ready money ffor a build?

Do I make any sense...?

[btstarcher]

One quick question: did you follow the dry compression test with a wet test?

[Ziggo]

I agree with the above, smells like ringlands cracking to me. Repeat the compression check wet and come back with results.

Manufacturer rating also includes a cylinder to cylinder max variance which this exceeds.

Zigatapatalka

[mrQQ]

if it's ringlands, what would wet test show?

what about the question that it's still o2 sensor causing the symptoms, and this being just a separate problem?

[Ziggo]

And yes, this could cause the fueling to go wonky

Zigatapatalka

[btstarcher]

There's now way to really know for sure about the O2 sensor being a separate issue, so I'd try to fix whatever is causing your compression problem and then see if the fuel trims come back in line.

It's interesting to note that my trims have been slowly increasing as well, and my compression in cylinder 3 is shitty. I'm pretty sure my O2 sensors are fine. My compression issue's root cause lies somewhere in the top half of the engine though. Probably.

[mrQQ]

hm, well, since it's much easier to fix o2, i'll try to start with that and see how that goes.

another thought - could injector seals be a cause?

[btstarcher]

Well one thing I'm sure of, the O2 sensor won't fix anything. Not until you deal with the compression issue.

[mrQQ]

yes, but shouldnt 9 be enough for engine to still run pretty normally?

[btstarcher]

It's not the AFR causing the crappy running. It's your shitty compression. Ask me how I know LOL. You asked if the compression was causing the rich AFR's; it's possible that your compression problem is the only one. However that doesn't make the opposite true.

[mrQQ]

yea i know, but the fact is, that my o2 sensors still read different, its running damn rich, plugs are black, narrowband reads 0.7v (rich), but wb reads 1.0000, stoich. so i'm thinking, perhaps the worst symptoms are caused by the o2 sensor, but, ofc, shitty compression doesn't help.

[8.5MS3]

stop trying to beat around the bush

motor needs to be yanked and the low cylinder needs to either be replaced or the whole block machined and rebuilt

calibrating sensors to mask a mechanical problem will only cause you to vent the block, leaving absolutely nothing salvageable

do it right

[mrQQ]

i'm not making any decisions yet, I'm just gathering information.

the biggest problem by far, is that I don't have access to parts. Ring set from dealer costs 500$ here, it costs 150$ at your place. So I have to measure all my moves. Even if I order from US, it still is like 3 weeks or so of delivery/clearing time, so I need to time my shop work very accurately.

Thats the reason why I'm trying to calculate my moves. If I had access to the parts like you guys have, I could just say fck it and build the motor, but I dont, so I need to figure out what to do.

[Ziggo]

Its unlikely that it is just the rings.

What the wet test does is rule out problems with the valves/valve seats. If the compression goes up wet then the valves and valve seats/guides are not the issue

Zigatapatalka

[atvfreek]

Originally Posted by mrQQ yea i know, but the fact is, that my o2 sensors still read different, its running damn rich, plugs are black, narrowband reads 0.7v (rich), but wb reads 1.0000, stoich. so i'm thinking, perhaps the worst symptoms are caused by the o2 sensor, but, ofc, shitty compression doesn't help.

It's definitely not the o2 sensor that is bad, that is just telling you there is an issue. Having low compression will cause oil blow by which will show as rich, and it will also have an incomplete burn, which will show as rich.



Sent from your couch

I was the one that did a stock rod/piston swap for dougefresh to get him up and running. If you have any questions feel free to hit me up.

Sent from your couch

[8.5MS3]

sorry op, forgot you were international

what about scrapyards for cx7 blocks?

[mrQQ]

Originally Posted by atvfreek It's definitely not the o2 sensor that is bad, that is just telling you there is an issue. Having low compression will cause oil blow by which will show as rich, and it will also have an incomplete burn, which will show as rich.

but why does narrowband show rich wile wb show stoich?

Originally Posted by 8.5MS3 sorry op, forgot you were international what about scrapyards for cx7 blocks?

thought about that, but nothing, or even if there are, they are crazy expensive...

[atvfreek]

Originally Posted by mrQQ but why does narrowband show rich wile wb show stoich? thought about that, but nothing, or even if there are, they are crazy expensive...

The narrow band is actually a good indicator of how the car is running. The ecu can compensate through ltft/stft to make the wide band read correctly, therefore it can be hard to diagnose.

If the engine has a slight misfire/incomplete burn, you can determine from the narrow band whether its a rich or lean misfire. That's also why the ecu can set a p2096 code which is "post catalyst lean" it is monitoring the rear o2 and seeing that condition.

Edit: I personally would not throw an o2 at the car. Especially knowing there is a mechanical issue. All mechanical issues need to be addressed any electrical components is replaced.
Sent from your couch

[TiGraySpeed6]

RE: Injector seals as cause of compression loss-

With losses that bad you'd clearly be able to hear the seals venting as a popping kind of sound. Additionally you would be able to visually identify an oily looking residue in the area around the injector.

Since you're still on the K04 it's highly unlikely to be the seals but anything is possible. I wouldn't bet money on this being the issue tho.

It would, however, be a worthwhile thing to swap in a set of CPE seals while your doing all this work however.

[mrQQ]

ok, so I need to prepare the parts. Which parts do I need if I decide to:

a) just fix everything oem way
b) possibly upgrade internals

I've read that sleeves are not replaceable in this engine.

might be looking to buying bnr s3 eventually, but definitely nothing else.

[TiGraySpeed6]

There have been a few projects that included sleeves here, but I've no idea of the costs involved.

Just one quick example of sleeving the MZR is the cpe stage 3 short block

Here's one of the builds-
Nothing special

[Lex]

How many conclusive ringland failures have we had leading to these symptoms? I know of 2 (Dano, BlueStreak) yet I know of lots of cars with low compression numbers. Who else can chime in with the failure when they pulled the motor apart with low compression?
@BlueStreak; did you guys take that motor apart yet that had low compression numbers?