[weehe126]

At ~98k miles I installed a Pure Stage 2 and have been running 20psi with E30. For the first time since owning the car (46k miles), I got the low oil, add a quart light. Thinking it was a fluke the first time, I didn't document the mileage. I have gotten the low oil light 3 more times now, every 1500-2000 miles.

I started getting a stumble at idle, so replaced my plugs (they had 12k miles on them). All plugs but cylinder 4 looked new.


The base and insulator has carbon deposits, while the electrode is crusty white.

This made me pretty concerned so I did a compression test:
C1-200
C2-160
C3-190
C4-185
C5-200
C6-160

Not really what I was expecting, now I'm concerned about C2 and C6 as well. I also took pics of the new plugs after 300 miles. C4 already had deposits.

The rest looked brand new:


My next thought was a bad PCV valve in the valve cover causing oil vapors to get sucked into C4. I pulled the intake manifold, but there was no oil residue on the intake track or valves. I also confirmed the main PCV valve is fine with the vacuum test. So oil is coming from after the intake valves.

Lastly, I checked all cylinders with a scope. C4 piston was dark brown, burnt oil. All the others looked normal with a little carbon deposit on the sides. There was no visible damage on any cylinder wall, or on the edge of the pistons/rings.

So I am at a loss. The car still drive great, only with the occasional stumble at idle. I know these engine can bend rods and oil consumption is the only indicator.

Is there anything else it could be? I'd rather not wait for it to pop to find out.

[JETmn]

I would expect a weak coil causing it or possibly a bad injector. More concerning is the white buildup on the electrodes for the other plugs. It almost looks like aluminum deposits, hard to tell from the picture. Have you been logging at all?

[Jeff@TopGearSolutions]

Compression and leak down test?

[JETmn]

Originally Posted by Jeff@TopGearSolutions

Compression and leak down test?

Compression is in the middle of his post, but he didn't do a leak down that I can see. I never trust a compression test unless it was done 3 times with very close results. It is very finicky with getting the adapter seated properly and just a tiny leak throws things off drastically.

[weehe126]

I log almost every pull I do. Nothing stands out, no extra timing pull on C4, and avg_ing stays below 1 all the time.

I did C2,4 and 6 compression test 3 times each. I also cleaned the seat a bit to see if there was a leak, but results were within 15psi. C4 did drop to 165 as the very last measure, but that could have been from the oil cooling.

I'll take a closer look at the old plugs. Nothing stood out, but I'll get a better pic of the electrode.

One thought I had was a bad injector. I swear I got a low oil light very soon after installing the PS2 and have wondered if it has a bad seal. The oil consumption could be unrelated to the plug deposits and dark piston and just be coincidental.

Edit: coils and plugs were replaced 12k miles ago. Then replaced the plugs again now.

[Jeff@TopGearSolutions]

Originally Posted by JETmn

Compression is in the middle of his post, but he didn't do a leak down that I can see. I never trust a compression test unless it was done 3 times with very close results. It is very finicky with getting the adapter seated properly and just a tiny leak throws things off drastically.

Ah I see that now, inconclusive.

[HawkeyeGeoff]

Those compression numbers are kind of all over the place. What's the spec on % difference per cylinder? On previous platforms I know you usually want all cylinders to be within 5-10% of each other.

No leaks anywhere?

I had a vacuum leak, caused bouncing idles. Fixed it via new valve cover gasket+pcv valve, new sparks, coils, reset all my adapts and boom all set. No outside of norm fuel trims? Any logs?

[JETmn]

Originally Posted by weehe126

I did C2,4 and 6 compression test 3 times each. I also cleaned the seat a bit to see if there was a leak, but results were within 15psi. C4 did drop to 165 as the very last measure, but that could have been from the oil cooling.

Did you take the spark plug adapter out each time? That is the biggest issue normally is that some small piece of gunk gets in there and creates a small leak. How many revolutions did you do on each test? A leakdown is very nice too if you have the tester. Like was mentioned earlier you can put a small amount of oil in the cylinder too to try and seal the rings better to see if it gets better.

A boroscope that goes on your phone is very cheap also (like $20) and they actually work pretty good. Another option if you are thinking there is any damage, but I wouldn't at this point. I would redo the full compression test twice more and see how they all match up. If they are consistent then a leakdown is in order. If there is still a problem you are probably going to be looking at injector seals, head gasket or valve seals/seats.

[weehe126]

This was my first compression test, so I very ell could have messed it up. Thinking about it, I'm not sure where each piston started. So the low results could have started at TDC, not sure if that would matter.

I have plenty of logs with consistent trims over the last few months. I don't have any leaks and not sure how that would cause oil consumption or excess carbon on a plug/in a cylinder.

[MiamiM3]

Originally Posted by weehe126

This was my first compression test, so I very ell could have messed it up. Thinking about it, I'm not sure where each piston started. So the low results could have started at TDC, not sure if that would matter.

I have plenty of logs with consistent trims over the last few months. I don't have any leaks and not sure how that would cause oil consumption or excess carbon on a plug/in a cylinder.

What ended up being the outcome?

[weehe126]

Swapped the injector and it runs smoother. Haven't had a chance to pull the plug and scope the cylinder. Injector was definitely bad, but haven't confirmed if there are any other issues.

[weehe126]

Update: Car has been driving fine for the last 5500 miles. Recently it has started to buck when the engine is cold, just like before. It drives fine after 2-3 minutes, with minor hiccups/misfire feel at idle. Oil consumption is still a quart per 1000-1500 miles. I replaced the plug on cylinder 4 and it fixed the bucking for a day. I have a new injector I will be putting in soon to see if it fixes it again. I changed the oil and noticed a significant (3-5x more than normal) amount of magnetic material built up on my magnetic drain plug. I am not sure what engine material is magnetic, but I did add at least 3 quarts of Rotella T6 oil between changes.


I installed MILVs about 2500 miles ago and noticed an odd sound with the engine cover off/oil cap open. Sounds like a slapping/metallic ting sounds. I'm concerned it is rod knock, but it could also be the crankshaft slapping the oil. Hasn't changed over the last 3000 miles. Let me know what you think.


Here is a pic of the cylinder 4 plug after 5000 miles. One side looks fine, other has white crust on it:



Here is a video of the sound I mentioned:

[ap485]

Originally Posted by weehe126

Update: Car has been driving fine for the last 5500 miles. Recently it has started to buck when the engine is cold, just like before. It drives fine after 2-3 minutes, with minor hiccups/misfire feel at idle. Oil consumption is still a quart per 1000-1500 miles. I replaced the plug on cylinder 4 and it fixed the bucking for a day. I have a new injector I will be putting in soon to see if it fixes it again. I changed the oil and noticed a significant (3-5x more than normal) amount of magnetic material built up on my magnetic drain plug. I am not sure what engine material is magnetic, but I did add at least 3 quarts of Rotella T6 oil between changes.


I installed MILVs about 2500 miles ago and noticed an odd sound with the engine cover off/oil cap open. Sounds like a slapping/metallic ting sounds. I'm concerned it is rod knock, but it could also be the crankshaft slapping the oil. Hasn't changed over the last 3000 miles. Let me know what you think.


Here is a pic of the cylinder 4 plug after 5000 miles. One side looks fine, other has white crust on it:



Here is a video of the sound I mentioned:

Have you consider doing an oil analysis?

Now that you installed the MILVs, have you tune your car for the additional intake lift? dyno?

[weehe126]

Originally Posted by ap485

Have you consider doing an oil analysis?

Now that you installed the MILVs, have you tune your car for the additional intake lift? dyno?

Was debating an oil analysis on this oil change, wish I had done it. I will be doing one on my next change assuming the engine keeps going till then. Based on only having cold start and idle stumble, I'm wondering if I have a bad valve seal instead.

I adjusted the one table currently available in the XDF for valve lift on pedal vs rpms. At the same psi I noticed my wgdc increased and the car feels faster above 4500 rpms. I have not done a dyno since I'm pretty sure something is wrong with my engine lol. Wouldn't want to post low number and everyone flip out.

[MTK24]

doesn't look good. The turbo upgrade didn't cause it, it just brought out issues you already had and made it more noticeable.

Did you do a compression test after replacing the injector? You also already diagnosed the burning oil is not from anything minor. I would recommend selling the car because it looks like a ticking time bomb

[Bours]

Update ???

[weehe126]

Replaced #4 injector and plug again and everything is good. A new plug and injector every 6 month is fine by me at this point. With the added MILVs and 7.5" race IC it is pulling the hardest it has ever. If I do ever have a serious engine problem I plan to build it. Just need to wait for someone to show a working built N55.

[Bours]

Originally Posted by weehe126

Replaced #4 injector and plug again and everything is good. A new plug and injector every 6 month is fine by me at this point. With the added MILVs and 7.5" race IC it is pulling the hardest it has ever. If I do ever have a serious engine problem I plan to build it. Just need to wait for someone to show a working built N55.

im rebuilding mine at mmp ( its getting shipped tomorrow )
|

coated main and rod bearings, coated pistons, maching the crank, proper clearance . new gaskets etc...

im still debating if i should add forged rods..

thoughts ?
|

i know its not a full build but a guy in another thread is doing the first real full build so you can check that.

im wondering what can cause your trouble with cylinder 4 tho

[weehe126]

If I were to do a build I would do upgraded rods. Basically the same price as stock, so not sure why you wouldn't.

I either have a leaking valve seal, cracked ring or bent rod. Will drop the turbo one of these days to see if it is the seal. Stage 1 head would be nice over a engine build.

[Bours]

Originally Posted by weehe126

If I were to do a build I would do upgraded rods. Basically the same price as stock, so not sure why you wouldn't.

I either have a leaking valve seal, cracked ring or bent rod. Will drop the turbo one of these days to see if it is the seal. Stage 1 head would be nice over a engine build.

Do.you have a knocking noise when you rev it ?

Forged rods are a 1800 usd option...
They can reuse my oem if i want but im.not 21 psi on ps2 + meth is enough torqu to bend ap rod right ?

They do all seals ( valve and exaust )

[weehe126]

I do not have a knocking sound. If I were going through an engine build I would not use stock rods.

[Bours]

Originally Posted by weehe126

I do not have a knocking sound. If I were going through an engine build I would not use stock rods.

why ? stock rods are supposed to handle 600 wtq but you might be right and i think ill go forged rods for peace of mind