Engine/Transmission (1998.5 - 2002) Intake valves

[Wyomingcowboy]

As I pulled all of my valves tonight in the last phase of my teardown, I noticed a tremendous amount of gunk on the intake valves. I also have a bunch of oily crap in the intake mounted on the head. The intake horn and intercooler hose are as clean as a whistle. What gives?

 

[DCreed]

do you have a EGR?

 

[Wyomingcowboy]

Ummmm... ..... IDK!



I don't think so... .

 

[DavidC]

Probably from Exhaust Brake. That is why you need to clean the intake air sensor once in a while. That's my guess.



Dave

 

[Bob4x4]

No egr on the 01's

 

[Wyomingcowboy]

How would an intake air sensor lead to build-up? And my exhaust valves are fine. A little bit black but no buildup. I don't understand how an exhaust brake could do that either. I have only had it on there for about 5k miles and due to a bad air cylinder I have not used it much at that.

 

[DavidC]

When the EB is active the valve train is still opening valves as usual and some of that soot gets pushed into the intake because the exhaust pipe is being restricted. When this happens the intake air sensor also gets soot deposited on it which can insulate the sensor and cause some minor fluctuations in the readings from that sensor, usually poor fuel mileage.



Dave

 

[Wyomingcowboy]

would the soot buildup on the intake valves be wet in nature?

 

[DavidC]

No definate answer from me on the wetness altho some fuel and probably cylinder oil would probably be blown into the intake to some extent. I know when I clean my IAT it is a little damp altho I never need to add oil so it must be minute amount but enough to give a wet appearance.



Dave

 

[Wyomingcowboy]

the nasty crap build-up is tacky.

 

[BlitzkriegSSII]

I had the same thing about a year ago on my 02.



The valve guides and seals were worn. The exhaust side had some of the seals blown off and missing some of the rubber. My truck would burn some oil when i started. I believe pulling hard from Va. to Alaska didnt help any. Egt's were between 1,100 and 1,250 for 5,000 miles. It even melted the mud flap :-laf.

Other then the valves every thing looked good. All i did was put in new valve guide seals and lap the valves. Got another head in the work.



The valve stem should be at a min of 0. 2752in to a max of 0. 2760, and the valve guide bore should be ? (my factory service manual shows checking it but does not give the number as to what it should be, maybe some one can tell us).



Hope this could be some help to you. Have some pics if it may help.

 

[DavidC]

TTerry,

At what mileage?



Dave

 

[cruiser_2]

Well folks since there is a valve overlap (a point at which both intake and exhaust valves are open at the same time) there is a possibility that some buildup on intake valves are possible. Valve overlap is used to help bring in fresh air (and in the case of a gas car air fuel mixture) by leaving the exhaust valve and intake valve open for a brief perion and the gasses that are flowing out the exhaust help pull in fresh air. From a technmical side that would be the only place where I could see that happening.



John

 

[DCreed]

I dont believe turbo charged engines have overlap in the cam profile as there is no need for it and it would cause back feeding as the exhaust has drive pressure.

 

[Wyomingcowboy]

So where would the wetness/tackiness come from? If the brake is on there is no fueling and therefore nothing in the cylinder besides hot air, correct?

 

[Wyomingcowboy]

OK, so I was just reading out of an auto book that I assigned to my students and it's talking about the PCV valve and how if it becomes plugged oil can be forced into the air cleaner or it can be drawn into the intake manifold. Obviousley we don't have a pcv valve in that sense and it's not going to force oil all the wway back through the intercooler, turbo and back to the air cleaner, but we do have a blowby valve. Could that be my problem? It not quite working right and drawing oil into the intake?

Just a thought... . perhaps I should read what I assign to my students also

 

[FosterW]

What do you teach?

 

[Wyomingcowboy]

auto:-laf



poor kids!





I know enough to teach HS obviously, I am learning alot as we go too, but welding is what I really wanted. But, life happened and here I am.

 

[DCreed]

did the valves have proper lash? if they were set too tight the gunk in the cylinder will blow past and into the intake during combustion.

 

[Wyomingcowboy]

There's no telling now... I'll make sure I get em set when it goes back together.