Pulled the plugs, please help me read them

stangGT97

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• Oct 16, 2006

• #1

Over the weekend I installed a set of AGSF-22C plugs in my 97 GT. Up until now I was running the stock replacement Motorcraft Platinums, and those had only been in for about 10K miles. Now I noticed something really funky upon removing the platinum plugs:

Drivers side - All four plugs have deposits, distinctly brown on the white ceramic part, so I can clearly see what direction the air/fuel mixture is traveling in relation to the electrode. Electrode looks fine, no signs of pre-ignition, seems to have normal wear.

Passenger side - I can't hardly find any deposits on the plugs! I mean they look like they were just put in a couple of weeks before. Electrode looks fine.

I probably never would have made any sort of correlation had I not been indexing the new plugs. My car is not throwing any codes either. But why would there be such a difference in wear between the two banks? What's at work here? Thanks a lot!

 

jstreet0204

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#2

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My guess would be it is a lazy o2 sensor on one side. The EEC adjusts fuel for both banks independently, so if one o2 sensor is off a little it will add or subtract more fuel on that side.

 

BooWFO

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How are people suppose to help you read them with just a discription?

But I'll take a stab in the dark. Is it possible that one bank is running richer than the other. Possible things could be 02 sensors giving funky readings, injectors dirty, coil pack going bad, one side (clean side) getting moisture in and steam cleaning the plug, or could be one side was facing the charge and firing cleaner.

 

stangGT97

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#4

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BooWFO said:

How are people suppose to help you read them with just a discription?

But I'll take a stab in the dark. Is it possible that one bank is running richer than the other. Possible things could be 02 sensors giving funky readings, injectors dirty, coil pack going bad, one side (clean side) getting moisture in and steam cleaning the plug, or could be one side was facing the charge and firing cleaner.

Click to expand...

sorry BooWFO, I'm at work so I figured I would use my lunch break to post my problem. I'll take pictures when I get home and put them up, I should have thought of that before

-O2 sensors are bosch sensors, put on about a year ago. Correct me if I'm wrong but it would be the two sensors right by the manifolds that would affect the A/F ratio, right? Who knows, maybe they're just crappy sensors.
-Not sure about the injectors, though I had them out when I replaced my manifold (month ago) and they appeared to be ok. Two had cracks in the plastic tip though, but 6/8 looked like new
-Coil packs are two months old, wires are Motorcraft 8mm, and have ~7k on them
-What would be a possible way for moisture to enter the cylinders? I do notice that if my car sits for over a day in the cold, it studders on first start up. might be a moisture issue.

Sorry, I know internet diagnosis is difficult, I'm just curious about this trend that I'm seeing. Thanks.

 

jstreet0204

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#5

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Yes, the o2's closest to the manifolds are the ones used to adjust fuel. Injectors or coil packs are unlikely if the entire banks are similar. I've had brand new bosch o2 sensors from a parts store, that were lazy. They can be off just enough to skew the fuel trims, but not throw a code. Bosch o2's from a dealer will be more accurate, but yours are probably not off enough to hurt anything.

 

stangGT97

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#6

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jstreet0204 said:

Yes, the o2's closest to the manifolds are the ones used to adjust fuel. Injectors or coil packs are unlikely if the entire banks are similar. I've had brand new bosch o2 sensors from a parts store, that were lazy. They can be off just enough to skew the fuel trims, but not throw a code. Bosch o2's from a dealer will be more accurate, but yours are probably not off enough to hurt anything.

Click to expand...

Hmm, interesting you should mention that. My four sensors came from 3 different shops (don't ask why). Two from an online parts store (forget the name), one from an ebay store, and one from Autozone. AFAIK they are all the same part #, and for certain the two front sensors are the same.

jstreet, do you remember my 1400rpm buck thread from a while back? I almost wonder if these two things are related. Man that would burn me up if I dropped all that money on new sensors and they're crappy. For what its worth, my gas mileage hasn't been too great lately and I'm light on the throttle (highway commute).

 

jstreet0204

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It could be related. I don't remember your mods, but if you have a way to datalog the fuel trims and o2 voltage, you could swap the o2's and compare the readings. If the fuel trims follow the o2 sensor, you'll know that is the problem.

 

stangGT97

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jstreet0204 said:

It could be related. I don't remember your mods, but if you have a way to datalog the fuel trims and o2 voltage, you could swap the o2's and compare the readings. If the fuel trims follow the o2 sensor, you'll know that is the problem.

Click to expand...

I don't have an handheld tuner yet, hopefully sometime in the future... but until then, datalogging won't be possible. Fuel trim stuff doesn't make much sense to me, this is my first Mustang so I'm new to tuning and such. Also, the only real mods I have are the PI intake manifold and catted X pipe

 

mstngjoe

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#9

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Spark plug tech:

http://www.dragstuff.com/techarticles/how-to-read-plugs.html

 

jstreet0204

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#10

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stangGT97 said:

I don't have an handheld tuner yet, hopefully sometime in the future... but until then, datalogging won't be possible. Fuel trim stuff doesn't make much sense to me, this is my first Mustang so I'm new to tuning and such. Also, the only real mods I have are the PI intake manifold and catted X pipe

Click to expand...

I wouldnt worry about it too much. It doesn't sound like the plugs were showing signs of a major problem, just a slight difference from one side to the other. Once you get a hand held tuner, dig into it a little further.

 

Warrior 102

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Oct 16, 2006

#11

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Make some pictures!

 

stangGT97

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#12

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jstreet0204 said:

I wouldnt worry about it too much. It doesn't sound like the plugs were showing signs of a major problem, just a slight difference from one side to the other. Once you get a hand held tuner, dig into it a little further.

Click to expand...

Ok, thanks man. Just out of curiosity, if the plastic tip on my injector has a crack, could that affect anything?

 

jstreet0204

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#13

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stangGT97 said:

Ok, thanks man. Just out of curiosity, if the plastic tip on my injector has a crack, could that affect anything?

Click to expand...

Possibly, but you'd see the difference in that particular plug, not the whole bank.

 

BooWFO

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#14

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jstreet0204 said:

Possibly, but you'd see the difference in that particular plug, not the whole bank.

Click to expand...

True but doesn't the entire bank get corrected by the o2 sensors reading? Could a messed up injector and a lazy o2 cause a fueling issue?
Just wondering for my own knowledge.

 

stangGT97

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Ok so here are the pics. Sorry about the quality, I suck @ photoshop and my camera hates closeups. I tried focusing on where the largest deposit buildup was

Drivers side:




Passenger Side:





As you can see, the passenger side plugs are still white, while the driver side are browned

 

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Warrior 102

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Jan 22, 2003

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#16

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Thy look good from my house,but yes the one side looks little darker than the other,I say check your O2 sensors.
Good luck.

 

jstreet0204

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#17

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BooWFO said:

True but doesn't the entire bank get corrected by the o2 sensors reading? Could a messed up injector and a lazy o2 cause a fueling issue?
Just wondering for my own knowledge.

Click to expand...

A bad injector would cause that bank to read lean or rich at the thus cause a correction for that bank, but the one plug with the bad injector would still show signs of being leaner or richer than the others.

 

Warrior 102

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#18

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By the way here is the plugs from my air cooled bike,this is after costume tunning,they should have little tan on them,that is what I was told by my tuner.

 

stangGT97

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Oct 18, 2006

#19

• Oct 18, 2006

• #19

Well I appreciate everyones input here. I think maybe I just worry too much about my car

But anyway, jstreet and BooWFO if you look at this, I posted pictures of the plugs a few posts up in case you're interested in taking a look.