3 dirty intake runners?

Duc_Z09 · 07-26-2015, 04:42 PM

I changed out to NGK iridium plugs today (coming from a Mustang, this car is a PITA to work on

) and noticed something weird. Intake runners on 2, 4, and 6 were noticeably dirtier than the other 3. I know I could just get Kenchan to photoshop my pic and make everything ok again, but I'd still like to know the cause...

SouthArk370Z · 07-26-2015, 05:01 PM

Aren't 3 of those for exhaust? If you mean the front intake is dirtier than the other two, I'd say that's normal. Possibly the EGR or some other pollution control that dumps toward the front of the engine.

kenchan · 07-26-2015, 05:03 PM

Duc_Z09 · 07-26-2015, 05:13 PM

Quote:

Originally Posted by SouthArk370Z

Aren't 3 of those for exhaust?

I highly doubt it since they go directly into the plastic intake plenum. Plus they're not nearly dirty enough for that... just oily.

I'm going to feel incredibly stupid if you're right though.

kenchan · 07-26-2015, 05:21 PM

u still want me to photoshop?

Jordo! · 07-26-2015, 05:29 PM

It's probably just a characteristic of differences between the banks -- there's usually at least small differences in mixture/AFR correction due to sensor variation.

EGR valve location may enter into it as well as SouthArk suggested.

Overall, I'm guessing its normal.

SouthArk370Z · 07-26-2015, 06:35 PM

Quote:

Originally Posted by Duc_Z09

I highly doubt it since they go directly into the plastic intake plenum. Plus they're not nearly dirty enough for that... just oily.

I'm going to feel incredibly stupid if you're right though.

I was looking at it cross-eyed. You are correct.

SouthArk370Z · 07-26-2015, 06:42 PM

Quote:

Originally Posted by Jordo!

It's probably just a characteristic of differences between the banks -- there's usually at least small differences in mixture/AFR correction due to sensor variation.

EGR valve location may enter into it as well as SouthArk suggested.

Overall, I'm guessing its normal.

But there is sooooo much difference between the two banks. The slight differences in the even-numbered bank looks normal to me (recirc, &c). Even the "dirty" odd-numbered bank don't look all that bad (dirtier than what I'd like to see, but I've seen worse). The fact that the odd- and even-numbered runners are so different worries me.

But I've already proven that I'm no expert.

DEpointfive0 · 07-26-2015, 08:04 PM

Mine is similar, not sure which is more discolored though, it's been a while since I took the mani off

Duc_Z09 · 07-26-2015, 08:54 PM

Quote:

Originally Posted by SouthArk370Z

The fact that the odd- and even-numbered runners are so different worries me.

Yeah, that's what makes me nervous. If they were all clean or all semi-dirty I wouldn't have thought twice about it.

Quote:

Originally Posted by kenchan

u still want me to photoshop?

Can't hurt.

phunk · 07-27-2015, 06:57 PM

The one and the only thing that travels through the lower intake manifold runners aside from intake air, is PCV system re-circulation.

Its just PCV oil not being evenly distributed. While it leaves a film on the runners, its effects to engine performance are negligible.

Duc_Z09 · 07-27-2015, 07:29 PM

Quote:

Originally Posted by phunk

The one and the only thing that travels through the lower intake manifold runners aside from intake air, is PCV system re-circulation.

Its just PCV oil not being evenly distributed. While it leaves a film on the runners, its effects to engine performance are negligible.

Thanks! I was concerned for a moment.

DIGItonium · 07-28-2015, 09:16 AM

It's the same for mine and others if you do a search. Catch can is probably on my favorites now because 25 miles is still enough to leave oil residue.

Duc_Z09 · 07-28-2015, 05:21 PM

Just for laughs I should go to the Nissan dealership just to find out how much $$ I saved myself by doing this...

DIGItonium · 07-28-2015, 11:47 PM

I don't even want to know with mine. I changed the valve cover gaskets, spark plugs, cleaned throttles, replaced throttle and manifold gaskets, and I'm currently replacing the upper intake manifold with a brand new one. The old one warped enough to cause vacuum leak.

Are you getting a catch can setup? I recently installed it, and the intake manifold is bone dry. It's really nice.

07-26-2015, 05:01 PM	#2 (permalink)
SouthArk370Z Premium Member Join Date: Nov 2010 Location: South Arkansas Posts: 8,435 Drives: 2014 Challenger Rep Power: 324197	Aren't 3 of those for exhaust? If you mean the front intake is dirtier than the other two, I'd say that's normal. Possibly the EGR or some other pollution control that dumps toward the front of the engine. __________________ Steering Lock Links - Search The370Z Bookmarklet - FSM @ NICOclub Mankind has progressed past the need for war but we haven't evolved that far. - NachoMahma Last edited by SouthArk370Z; 07-26-2015 at 05:04 PM.

07-26-2015, 05:21 PM	#5 (permalink)
kenchan A True Z Fanatic Join Date: Aug 2009 Location: N/A Posts: 76,801 Drives: N/A Rep Power: 141520	u still want me to photoshop? TerribleONE, JARblue and MicntaeG35 like this.

07-26-2015, 05:29 PM	#6 (permalink)
Jordo! A True Z Fanatic Join Date: May 2010 Location: nirvana Posts: 6,394 Drives: 2023 NATM Rep Power: 417	It's probably just a characteristic of differences between the banks -- there's usually at least small differences in mixture/AFR correction due to sensor variation. EGR valve location may enter into it as well as SouthArk suggested. Overall, I'm guessing its normal. __________________ Enjoy it. Destroy it.

07-26-2015, 08:04 PM	#9 (permalink)
DEpointfive0 Premium Member Bitches Join Date: Jan 2012 Location: SoCal Posts: 14,824 Drives: a lot Rep Power: 17151	Mine is similar, not sure which is more discolored though, it's been a while since I took the mani off __________________ Do YOU want to know what/where I got my username from? ( Click to show/hide ) NSFW due to language:

07-27-2015, 06:57 PM	#11 (permalink)
phunk A True Z Fanatic Join Date: Mar 2009 Location: Chicago Posts: 3,655 Drives: 370 Rep Power: 944523	The one and the only thing that travels through the lower intake manifold runners aside from intake air, is PCV system re-circulation. Its just PCV oil not being evenly distributed. While it leaves a film on the runners, its effects to engine performance are negligible. mayday813, JARblue, GaleForce and 1 others like this. __________________ Charles @ CJ Motorsports : Website \| Facebook \| Instagram \| YouTube Home of the 9 second, stock longblock, stock drivetrain 6MT 370z. 9.91 @ 142mph

07-26-2015, 05:03 PM	#3 (permalink)
kenchan A True Z Fanatic Join Date: Aug 2009 Location: N/A Posts: 76,801 Drives: N/A Rep Power: 141520

07-28-2015, 09:16 AM	#13 (permalink)
DIGItonium A True Z Fanatic Join Date: Jan 2009 Location: Kansas Posts: 3,800 Drives: 09 Z34-TT 6MT Rep Power: 42	It's the same for mine and others if you do a search. Catch can is probably on my favorites now because 25 miles is still enough to leave oil residue. __________________

07-28-2015, 05:21 PM	#14 (permalink)
Duc_Z09 Track Member Join Date: Jan 2014 Location: Frederick MD Posts: 876 Drives: With the blinker on. Rep Power: 23	Just for laughs I should go to the Nissan dealership just to find out how much $$ I saved myself by doing this... __________________ 2009 370z #206 (all mods are Home Depot) 2009 Ducati 848 (full Ohlins, Termignoni, etc) 2003 Grand Cherokee (long arms, big tires, 4.56, lockers)

07-28-2015, 11:47 PM	#15 (permalink)
DIGItonium A True Z Fanatic Join Date: Jan 2009 Location: Kansas Posts: 3,800 Drives: 09 Z34-TT 6MT Rep Power: 42	I don't even want to know with mine. I changed the valve cover gaskets, spark plugs, cleaned throttles, replaced throttle and manifold gaskets, and I'm currently replacing the upper intake manifold with a brand new one. The old one warped enough to cause vacuum leak. Are you getting a catch can setup? I recently installed it, and the intake manifold is bone dry. It's really nice. __________________

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