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Help Evaluate Spark Plug

pot

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Oct 28, 2003
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For the past three spark plug changes, the plug in cylinder number two always comes out looking like this. Otherwise, the remaining plugs look just fine. I have my suspicions on whats going on however I'd like to ask guidance from my seniors on whats going on in there.

These are NGK BPR6ES on 93 Octane. Coolant, oil, and fuel filter is changed regularly as per Owner's Manual. Boost is between 15 - 17 psi. Coolant temp as per VDO gauge (at waterneck) is 180 degrees farenheight. I have no aftermarket fuel management, nor have I logged any information in a while. Again, I have my suspicions but I'm sure this could be something I haven't even considered. Any help/assistance will be greatly appreciated.

 

fuel

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what's different from the other plugs? do they lack the white/tan looking electrode tip or do they not have the oil residue building up around the outside?

If it's the former I would say that cylinder is running leaner than the others (check injector flow rate and spray pattern) or if the latter I would say that cylinder is burning oil through either worn piston rings, cracked piston ring lands, a leaking valve stem seal or any combination of the three.

Having said that the whiteish/tan tip indicated it is running normal in regards to air/fuel mixture, however the spark plugs only tell the story of the last few moments the engine is running so while it may be OK at idle it could be a different story at WOT.
 

pot

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Compared to the other 3 plugs, this is the only one with the oil on the threads and white/tan tint on both the electrode and ground electrode. I replaced the valve stems last year and while the oil on the threads are a concern, my main concern at present is why both the electrode and ground electrode look the way they do. I think your right fuel, cylinder 2 injector may be clogged or not pushing adequate fuel. I appreciate your response brother.
 

fuel

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also over 15psi with nothing done to fueling is a bad idea.. assuming you're still on the 450cc injectors. Even with 510cc injectors it's running into dangerous territory with stock fuel system.

If you suspect it's an injector how bout you swap cylinder 2 to another cylinder and monitor the spark plug from now onwards?
 

pot

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I understand the fueling needs necessitate running conservative boost however I'm comfortable with between 15 - 17 psi. I want to rewire the fuel pump but I want to keep the car close to factory as much as possible at the same time. /ubbthreads/images/graemlins/dunno.gif -Guess I want my cake and eat it too. Nonetheless, the other 3 plugs are firing away just right.

If I may, do you think coolant is in any way shape or form corroding the plug or this plug just getting too damn hot? I have not noticed a loss of coolant but the tint of the plug is a tad bit green too.
 

turbohf

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my first thought was coolant. how long has that plug been in the motor? 10-15k?
 

fuel

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done a compression test then? though if coolant is leaking in through the head gasket you would expect to find an over pressurised cooling system too.
 

pot

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Fuel I think your spot on however I wanted to weigh multiple opinions. My compression test about 9k miles ago also, revealed compression in the 155's range across the board. I took a whiff of the coolant in the radiator and it didn't smell burnt however the recovery tank was looking a tad bit brown though but there was no odor also. I think your right I'm simply running lean. It was the faint green tint of the ground electrode that threw a wrench into things.
 

turbohf

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i have a buddy that put a THICK ass cometic gasket on his CRX (B18C) to lower the compression. always pushed a tad bit of coolant. infact im pretty sure to this day. has made 350-400hp for YEARS. still will say it pushes a little coolant now and again.


not saying its impossible. but it could be. im sure it doesnt take much to leave a little residue after 10k miles.
 

5OF2k

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Quoting Pot:
Fuel I think your spot on however I wanted to weigh multiple opinions. My compression test about 9k miles ago also, revealed compression in the 155's range across the board. I took a whiff of the coolant in the radiator and it didn't smell burnt however the recovery tank was looking a tad bit brown though but there was no odor also. I think your right I'm simply running lean. It was the faint green tint of the ground electrode that threw a wrench into things.



If you suspect you have a failing HG, the easiest way to check is to get a leakdown tester, pressurize the cylinder in question and the cylinders directly next to the cylinder in question with the radiator cap off, and watch for bubbles. If you're pushing coolant, you'll see it that way for certain.

Hope that helps!

-Jake
 

pot

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Jake I appreciate your feedback. I'm fairly well rehearsed in the diagnostic steps necessary to diagnose this particular issue. -Ultimately, I want to "read" this sparkplug and attempt to determine what the residue on the ground electrode is telling me.
 
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5OF2k

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Thats understandable man, for sure. Im having trouble seeing it or soemthing....? I dont see a green-ish tint personally....?
 

G

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pot

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Thank you G, the link was very helpful. Its nice to see your carousing the forum again. Where have you been? Well, I think I may have narrowed this concern coupled w/ Fuel's guidance to the following straight from G's link:

img.php


"This plug has ash deposits which are light brownish deposits that are encrusted to the ground and/or center electrode. This situation is caused by the type of oil used and adding a fuel additive. This condition will cause a misfire. This can be also caused by changing oils in midstream."

What does midstream mean?
 
Last edited:

fuel

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that plug example has obvious debris build up on it while yours only looks that way in colour alone (which to be honest is the colour a proper burn should be anyway). I would probably go as far as saying the other three cylinders are running richer than they should be. Though having a picture of the plugs from the other cylinders would be helpful.

Definitely swap injectors around and drive it a few miles then re-assess the plugs to see if it's cylinder specific or injector specific.

*edit* on closer inspection of your original plug picture it does seem yours does have some debris build up but not as bad as that example pic. Pics of the other plugs would definitely help though.
 
Last edited:

toybreaker

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Apr 30, 2006
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Quoting Pot:
Compared to the other 3 plugs, this is the only one with the oil on the threads and white/tan tint on both the electrode and ground electrode.



... that's one fluffy plug!

Can you post a pic of the other plugs?

Quoting Pot:
I replaced the valve stems last year and while the oil on the threads are a concern, my main concern at present is why both the electrode and ground electrode look the way they do.



Did you do the seals with the head in place?

Did you check the valve/guide clearance?

Was their oil in the exhaust ports?

Many times, when new seals are put on worn guides, the "fix" only lasts a short time.


Quoting Pot:
I think your right fuel, cylinder 2 injector may be clogged or not pushing adequate fuel.



... not so sure I agree with that hole being lean enough to matter on any significant level

Lean makes heat, and heat would turn that fluff to a hard baked glaze in a heartbeat on a hard pull.

I will agree you're probably getting close to running out of headroom with your fuel system, but my personal experience has been if you were trully flirting with disaster, the plug would have more of a white/yellow hard glazy appearance. (or, if things were really hammering, there'd be a scaled apperance and little balls of death making an apearance)

Listening to the injectors with a mechanics stethescope will tell that tale. An injector with a clogged last chance screen will give a noticeablly more hollow "click" when it fires.


My opinion is that the vast majority of what you are seeing on that plug is oil, plain and simple

... most likely from the guides

If it was getting past the rings, it *generally* glazes up the plug on a hard pull. The chamber temps are higher when the rings would be letting you down under boost, (allowing oil to enter the chamber/be "available" to make deposits.)

.. It would also increase the knock count considerablly.


Be sure to check the intercooler pipes, especially if you are still evacuating the crankcase into the inlet piping. Clean up any oil found there and monitor

Be sure to check the piping post turbo. Clean any oil found there and monitor


I'm half blind, but I can't see the green tint in that pic /ubbthreads/images/graemlins/dunno.gif

Many times, additives in the fuel can give a false coloring, but it's usually a more reddish/brownish tint.

With the shiat they call "fuel" anymore, the possibilities are almost endless on that front. /ubbthreads/images/graemlins/dunno.gif


These motors *generally* don;t allow coolant into the chamber ... without letting compression gases into the cooling system fairly quickly/soon after.

You would know pretty quickly if that was the case, as you'd be pushing coolant out into the reservoir on hard pulls.

You can use a five gas analyzer to sniff the coolant for h.c. if you suspect a teeny leak, but I would think a visual check of the combustion chamber would tell the tale.


... in fact, that may be your best bet at this point.

If you had any significant coolant in the chamber (enough to ash the plug) the piston in that hole would have a washed/clean/dryer appearance compared to the other holes.


My suggestion would be to look a little deeper at the motor the next time you have the plugs out. With the plugs out, turn the motor over with a wrench untill the exhaust valves are open on #2. My "guess" is that you'll see a gooey mess on the backs of the valves.


That said, I'd run it, and continue to monitor things.

The timing line on the ground strap looks good, and it hasn't glazed up.

Too many folks condemn motors that are still serviceable.

Watch for condensation and/or a funky sweet smell in the exhaust, monitor the coolant and oil levels more carefully

... and boost on /ubbthreads/images/graemlins/smile.gif

In fact, a hard pull every time you drive the car would go a long way towards keeping things tidy in the chamber. /ubbthreads/images/graemlins/devil.gif
 

pot

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Oct 28, 2003
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Location
Fayetteville, NC
I can't tell you enough Jon how much I appreciate your time and guidance ----it makes complete sense to me. I did replace the valve guide seals w/ the head on the car but I failed to consider checking the valve/guide clearance. There was a bit of carbon buildup on the ports during last exhaust manifold gasket change but it didn't appear to be significant accumulation.

Out of curiosity, if one cylinders valveguides are on their way out is that a sign the others are soon to follow suit?
 
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