suit in intake!?

[jheiv]

hey guys-- had a question that isnt really getting answered by other forums... this is where i should have started...

89 3.1 V6 Turbo
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I had a real rough idle, one cylinder w/o compression and a flooding problem, so I began taking apart my block. I noticed in the cylinder w/o compression (5th) there was a black suit going through the head and into the lower and then upper intake manifold. Any ideas how this would get there?

i have my specualtions (bad intake valve) but ill leave it up to the experts... any suggestions are greatly appreciated...

[AaronGTR]

Black soot you mean? I just took my engine apart and noticed a similar problem. Black streaks on the upper sides of the intake ports on the cylinder heads. My #6 cylinder has been having sporadic misfiring problems. Not sure what could be causing it. I noticed though that the #2 and #6 intake valves had some heavy deposits on them and there was a crack in the lower intake manifold gasket around #6. Any ideas?

My headers were leaking on the outside edge of the outer two tubes as well. I take the engine apart and start finding all kinds of problems. At least maybe when I fix it all it will be faster (I hope).

[xtremelumina92]

aaron PICS OF YOUR CAR!

[gpse3400]

Something isn't sealing. Zero compression and black soot....Bad valve most likely.

[AaronGTR]

It's weird though. The black stuff is only on the upper sides by where the head joins with the lower intake manifold, and it's on all the intake ports. Here's a pic of it. I'll post a link to all the pics of my engine work when it's finished.

[v6h.o.]

what you are showing there is absolutely normal.

its a combination of fuel, pcv fumes, EGR gases dirtying up the intake.

nothing abnormal there.

[5speedz34]

Hey, Aaron. Were do you live in Shelby? I live at 24 and Jewell.

[jheiv]

yeah thats nothing compared to what i have dude-- i shold take a pic later but its completely black

[johnc]

The egr valve sends exhaust gas right into the intake manifold to cool the mixture. If you have blow-by, or valve problems, it will be sent into the intake manifold and soot it up. Another indication that things are not right would be an aircleaner element with soot on it.

[Streetrodder83]

The carbon deposit is normal. It is caused from valve overlap, there is a point when both valves are open that slight reversion will occur causing the deposit of carbon in the intake. You also have the PCV depositing gases and other products of blow-by back into the intake. The purpose of the EGR isn't to cool the mixture but the combustion chamber at cruise to allow the running of a leaner A/F ratio, and to reduce NOx emissions. As you can see there are a few contributors to the problem.

[Scott_68B]

I thought the purpose of the EGR was to replace some of the oxygen in the mixture with an inert gas in order to reduce combustion temperatures, is this incorrect?

Scott

[geoffinbc]

I thought the purpose of the EGR was to replace some of the oxygen in the mixture with an inert gas in order to reduce combustion temperatures, is this incorrect?

Scott

Yes your right. The other guy is wrong. EGR DOES NOT lean out the fuel mixture. EGR gas is inert and is like a filler. It takes up space that air and fuel would normally use. Decreasing the products of combustion and thus decreasing head temperatures reducing the possibility of pinging detonation and reducing NOx emissions.

[AaronGTR]

The EGR is hot too, which produces higher combustion temps when the engine is still cold, for cleaner cold start emmisions and quicker cat light off. At least thats what I've been told. Does anyone know exactly what the PCV system does and how I could change it? I thought it was just to equalize pressure in the crank case. I'd really like to re-route it or put a valve cover breather on it or something because I get a lot of oil residue deposited in my intake from it. I'm installing all this nice clean ported stuff right now and I'd kinda like to keep it clean if I can.

[AaronGTR]

Hey, Aaron. Were do you live in Shelby? I live at 24 and Jewell.

Hey, whats up. I live real close. 25 and mound, right next to the high school actually. My best friend lives on jewel by 24.

[Streetrodder83]

I didn't say the EGR itself leans the A/F ratio. Typically in a cruise situation, the computer will back off the injector pulse, creating a 15:1 to a 17:1 A/F ratio for gas mileage. Doing this only causes problems with NOx emmissions and obviously detonation issues. Like you said this is where the EGR comes in and introduces noncombustibles into the intake charge, which will allow for a proper A/F ratio, which maintains proper combustion chamber temps, preventing detonation and NOx emmissions, but using less fuel.