Pulled Intake Off Check Valves

[CamaroBarb]

Today I pulled the intake to inspect the valves as my gas mileage has started to go down a bit. Sure enough they are caked with thick carbon. I only use Pennzoil Plat and change every 4k, I'm surprised they look this bad. The rear cylinders are really bad, big chunks hanging off them. Very disappointed this looks like this @ 82k miles and was cleaned by the dealer @ 50k.

[Kessler]

catch cans?

[Bigdumogre]

Ever sea foam it? Do you have a catch can ?

[DSX_Camaro]

Yeah, oil doesn't make a lick of difference if you don't have the PCV system modified.

[CamaroBarb]

No catch can but i'm going to get one for sure. I'm just surprised the valves are this bad. I run it hard. I never tried sea foam etc because they claim it damages the pistons from the hard carbon. Going to get a blaster at Harbor Freight tomorrow and walnut media and blast it all off.

['10CamaroDude]

Catch can will delay the inevitable, but will not stop it. That's what happens
with Direct Injected motors. Fuel doesn't wash over the intake valves anymore, so
you get carbon build up. More so for repetitive short trips. I ran a DI engine for
243,000 miles, never had an issue, but, 450+ miles a day, 4-days a week. Never
really had the chance to build up a lot of carbon with the constant running and
heat.

The catch can will help a lot, but it won't stop it.

Camaro, I sealed the oil fill neck, at the valve cover, and I do not get any more
humidity on the under side of the oil cap, it is now dry. IT doesn't have to move,
so I sealed it with weatherstrip adhesive.

[CamaroBarb]

Most all my driving is 25 miles one way so average is 50 miles on every start up. What does surprise me is its still very quick at WOT but I started noticing 2 things. Milage dropped from 25-26 local to 22-23 (i keep good records) and random miss fires at idle, cold and hot. Not enough to set a MIL but enough that you feel it. Sure enough if you look closely at the rear valve big chunks of carbon are breaking off in patches. I have to wonder why they didn't polish and coat the valves? Certainly if I ever pull the heads they will get done.

['10CamaroDude]

Polish and coat the valves? That won't stop carbon build up.

Misfire when the car is hot, is from a hot spot in the engine, you’ll get a lean misfire.
This is another side effect of DI engines. Since the intake valve opens into the
combustion chamber, it comes into contact with the byproducts of a misfire. During a
misfire, temps don’t reach the same level as during a full burn. Those un-burned
byproducts can stick to the neck of the intake valve and form deposits. Since the
back of the valve never gets cleaned by fuel, these valves are more prone to carbon
buildup and that buildup causes hot spots that create more misfires.

GM and Ford engines have a fraction of the carbon buildup complaints. BMW,
VW, Audi, and Porsche have far more carbon buildup problems than other brands.
The software that controls the direct injection process determines whether the
process will result in more carbon buildup. Apparently, the software designs for
BMW, Audi and VW result in excessive carbon buildup accumulation.

Gas treatments, and fuel injector cleaners will not prevent carbon built up,
because, as I said, fuel does not wash over the intake valves anymore.
On direct injection engines with carbon buildup on the valves, you need
and entirely different approach. None of the fuel injector cleaners will work
on that kind of carbon buildup because the fuel never touches the
valves.So you’ll have to inject the cleaner through the intake air duct
https://ricksfreeautorepairadvice.co...ction-engines/

[BRZN]

Noticed a slight "seat of the pants" misfire in ours. Had the 100,000 mile service done by the Chevy dealer, but could still feel it. Had a Check Engine Light come on twice, once before the service and once after with the code reading Random Misfire with the light being cleared and not coming back on.

I've installed a Catch Can that picks up a significant amount of condensation and oil, I drain it every other fuel fill up. I now put 6 ounces of Sea Foam in the crankcase about 150 miles prior to changing the oil, I run a can of Sea Foam through the intake Manifold prior to the Throttle Body just before draining the oil, and throw a bottle of CataClean in the fuel tank right after changing the oil. I've done this Sea Foam and CataClean process twice now and change the oil and filter every 3,000 miles. The first time I ran the Sea Foam into the Intake Manifold the amount of smoke coming out the exhaust was incredible! The second time, not nearly as bad, so I've got to assume the oil in the Intake Manifold is lessening, slowing down carbon build up on the valves and combustion chamber.

[CamaroBarb]

This is my 1st GDI and hopefully my last. I wonder what happens if you never clean the valves? I bought every thing I need to walnut blast them but I wonder how bad the CRC spray is to use in these engines. I used it once in a 8 cylinder PFI engine with high mileage and after the engine started using alot of oil. Qt every 300-500 miles. So I'm not too quick to try that again. I also seen in the link above the Sea foam can badly damage the cats because its combustible and overheat them. I was thinking about blasting the valves then use the CRC sparingly just to clean everything up a bit. Maybe use 1/4 of the can. Lastly adding a catch can.

[CamaroBarb]

Originally Posted by BRZN

Noticed a slight "seat of the pants" misfire in ours. Had the 100,000 mile service done by the Chevy dealer, but could still feel it. Had a Check Engine Light come on twice, once before the service and once after with the code reading Random Misfire with the light being cleared and not coming back on.

I have the same seat of pants feel misfire in mine at times. Mostly in 6 gear around 45 mph I can feel a slight misfire but its nothing really bothersome. I've heard alot of other people complain about it too. Using premium fuel its mostly gone. I'm on the fence what to do with this car. Trade it for a non GDI car or dig into solving the valve intake issue. My rear cylinder valves are badly carbon ed up, the frts don't look too bad.

I notice the oil getting into the intake is not only from the PCV valve but from the breather tube at the frt of the throttle body. When I pull that large hose off its always wet with oil. How do you stop that?

[BRZN]

With the Sea Foam into the Intake Manifold, I'm using the aerosol can and spraying it right at the throttle body at the air tube, where it connects to the throttle body with the tip that comes with the can. The air tube is re-connected to the throttle bottle sealing everything back up with the tip inserted. If I understand the workings of the computer, this spot should not be seen as unmetered air and not having more fuel dumped in thinking it's in a lean condition. The only extra fuel being burnt would just be that of the Sea Foam. The two times I've done it I've not had an issue. I use the CataClean in the fuel tank to clean any oil that's been sent through the combustion chamber to try to not have the cats be clogged.

You state above, "Lastly adding a Catch Can" I'd suggest that be added ASAP. It won't stop all the oil being sent in, but stops a great deal of it. In the 3,000 miles after installing it, the can was full! Since then I dump it at every other fill up.

[CamaroBarb]

I have bigger troubles now, for some reason since pulling the intake and reinstalling it the car runs much better at part throttle and the fuel mileage dropped dramatically from 23 down to 18. It also has alot more power pulling away from stops now I can easily spin the tires like never before. The only thing I did different than before was unplugging the MAP sensor. I've had the TB unplugged before. The car has always acted funny between 1/4 and 3/4 throttle. It would kinda go flat and lay down, now it doesn't do that. It just goes like it should. Perplexing for sure.

[CamaroBarb]

Originally Posted by BRZN

With the Sea Foam into the Intake Manifold, I'm using the aerosol can and spraying it right at the throttle body at the air tube, where it connects to the throttle body with the tip that comes with the can. The air tube is re-connected to the throttle bottle sealing everything back up with the tip inserted. If I understand the workings of the computer, this spot should not be seen as unmetered air and not having more fuel dumped in thinking it's in a lean condition. The only extra fuel being burnt would just be that of the Sea Foam. The two times I've done it I've not had an issue. I use the CataClean in the fuel tank to clean any oil that's been sent through the combustion chamber to try to not have the cats be clogged.

You state above, "Lastly adding a Catch Can" I'd suggest that be added ASAP. It won't stop all the oil being sent in, but stops a great deal of it. In the 3,000 miles after installing it, the can was full! Since then I dump it at every other fill up.

What can are you using?