COSPEED

The problem you face doing that is the deposits on a GDI engine are far greater than a old port injection engine, and the deposits are also hard and crystalline so when you do that procedure, you end up risking damage to the pistons and cylinder walls when the smaller particles break loose and are forced between the piston and cylinder wall and cause scouring (scratches).

What the OP and other are showing here are NOT tearing apart the engine, only removing the intake manifold which is very easy with minimal tools if your somewhat handy. All gaskets are reusable and this also allows you to properly clean the oil already pooled in your intake manifold to be cleaned as well.

After you remove the intake manifold place it up on end and let the oil drain onto some paper towel or rags on the floor, then spray a can of brake clean inside it and swish it around and drain that. Let dry and reinstall. If you need more instructions, the OP can probably chime in or I have it in the C7 tech section as well.

A471133

PM me if you guys have specific questions about the procedure not addressed in the DIY.

MikeinAZ

Thank you for the insight and warnings! What would be the difference though in running some cleaner through the PCV system vs. putting in a fuel treatment on a non GDI engine, you are 'washing' the intake valves in either case, would you not risk the same thing in deposits potentially getting into the cylinder? I do not want to do anything to risk damage so I was going to return the cleaner I bought but thought I would ask. Again, thank you again I appreciate it!

A471133

I believe in nonGDI systems, fuel is a solvent and is constantly washing the valves; if you ran quality fuel on that hypothetical car there would be minimal deposits on the valves to wash off with a treatment, and therefore should have minimal chunks/hard deposits flying off into the combustion chamber. This is different with GDI is no fuel is keeping the back of the valves clean, oil and dirty stuff gets stuck on the back of valves, and over time bakes into hard deposits that accumulate on top of each other.

FYREANT

Bingo.

robert miller

With time what ever get on the back of the valves will in time bake onto them. That is why on the z51 cars you need to run it with only 9 qts of oil & not fill it with the 9 plus.

If the car is run hard & get hot it will form over into the intake.

COSPEED

Correct!!! The issue is not only this, but port injection and carbureted engines the deposits were relatively soft carbon and could be loosened and expelled out the exhaust with little chance of damage. GDI the valves are operating at such high temperatures that this are very hard and abrasive, and the amount of build up is so far greater. Port injection, even w/out running top tier fuel will rarely ever have any deposits on the intake valves due to the constant cooling and washing with detergent fuel (all fuel in the US must have minimum detergent additives), so you can examine a port injection head and see zero deposits even after 100-200k miles. Now look at these new GDI and see them in 2-5k miles.

And the deposits that build in GDI engines are wearing the valve guides at all times, and you really don't want to do a treatment every 1000 miles. Eliminate the cause at the source, and don't have to worry about it.

MikeinAZ

Thanks guys!

COSPEED

Bumping this back up for those that are looking for how to perform this properly.

olddragger

Water methanol injection? Problem fixed. BMW has experimented with it.

COSPEED

Several problems with this. First, in order to be truly effective, the spray would have to be near constant. Most are boost referenced, so only spray during boost. Also, the cost to always refill the Meth is pricey in comparison over time to a proven system like the ColoradoSpeed or Elite Engineering E2-X system. Then one must look at the high compression ration of a DI engine (11.5:1 plus) will experience detonation as your introducing a combustible mixture to the cylinder during the compression stroke where pure GDI only introduces it milliseconds before ignition. SO this defeats one of the main advantages of GDI over Port injection. So yes, it does help slow the rate of coking, but is far from practical and is only partially effective.

stevebz06

While I admire your dedication to maintaining your car, I suspect that the average owner will quickly tire of doing this procedure every 5 or 10 K miles, especially if they have more than one DI engine to maintain. It's hard enough to get a lot of people to change their oil.

I have DI DD that has around 180K miles with no special attention paid to this issue, so I decided to give the CRC cleaner a try. I sprayed it thru the crank case ventilation tube inlet.

I think the car runs better but I haven't scoped the engine to see how clean the valves are.

So far, I'm pretty happy with the results.

cv67

Run decent gas
dont lug the engine
Run it hard occasionally

No reason to tear your car apart all the time but to ea his own

rcooper

Absolutely the best post ever for the C7! I know that I need to do this, but with 2 left hand and blind it is going to be tough to do.
I think that I will allow for a full day and no beers!
Thanks for this great post and the time you took to put it together, A471133.

fredmills

I would love to know what a GM service engineer has to say about all of this. Does it apply to my daily driver driven 5K miles per year.

Tron1

Does running the engine harder (keeping rpms up) as opposed to driving lazily (or slower with low rpms) help in diminishing coking on intake valves? If so, why? How does higher quality synthetic oil reduce coking problem?

MikeLsx

You probably caused more harm than good.

What happens is that pieces of carbon break off, and get stuck in the engine/behind the cats.

stevebz06

Time will tell but with the car approaching retirement I was willing to take a chance.

COSPEED

The only way you can safely use a solvent based upper induction cleaner on a GDI engine (due to the hard abrasive crystalline nature of these "hard" carbon deposits vs "soft" carbon of the past that could use them safely) is to start when new every 10-15k miles along with a proper air/oil separation system like the Colorado Speed or Elite E2-X systems. First, when you read the disclaimers on CRC/Seafoam/BG, etc. they clean "Up to 40%" (generally less than 20% is loosened). And when this occurs, it is similar to pouring some sand in your intake. The smaller hard abrasive particles are forced between the piston and cylinder wall resulting in scouring, a larger chunk sometimes becomes stuck between the valve and seat allowing piston contact and bent valves, and this damages all catalytic converters. If a turbo application, the impact of the pieces hitting the leading edge of the hot side turbine causes damage as well. So, these while great in the past for port injection and carbureted engines, are NOT safe for GDI engines. I do expect you loosened enough to run better, but remove the TB and scope the valves and see first hand how bad they are. What make/model/engine is it? Most the IM is easy to remove and inspect up close. That is the only way to see and verify. If you do a base line dyno, then manually clean and after dyd\no you will be shocked to see just how much power you lost over time gradually. If it is lost at one time, it is easy to notice. Not over time though until really running bad.

I agree that emptying a proper air/oil separation system every 5k is something 99% will not accept, that is why the "enthusiast" is generally the only owners to take these steps.

Can you give details on how "decent gas" helps this? All gasoline in the US has minimum dtergent additives, but now that no fuel touches the valves unlike in the past when port injection showered the valves to keep them clean, cool, and deposit free, fuel used has absolutely no effect on a GDI engine. Running it hard appears to help some in slowing the rate of growth, but the most important easy way to reduce the rate is ONLY run a full synthetic oil. The DEXOS blend has far too much conventional oil in it and cokes at several times the rate a good full synthetic does. Other than that, no additives, no top tier fuel, no magic in tank techron or other additives do anything now except help keep injectors clean, but as they now operate at 2,000-3,000 PSI vs port injection at 50-55 PSI, they rarely clog.

I am a past GM factory trained Service Tech as well as an Automotive Engineer that has worked in the industry for decades, and this is the worst issue to hit the industry ever as far as affecting almost all makes/models in the World. Ford techs are replacing failed engines right and left. GM is ignoring it claiming it "does not affect our engines" when of course it does. BMW is the most proactive with the crushed walnut shell media blasting equipment at most BMW dealers.

ALL service techs are instructed to not discuss this with the public.

Yes, and the reason is simple. Greater velocity of flow through the engine seems to not allow the formation as severely as driving easy. Similar to back in the days of carbureted engines and the "Italian tune-up" we used to do every few months. The oil is the biggest factor, and that is where SAE seminars are focusing currently. Full synthetic oil when burned leaves very little in the way of ash, deposits, etc. Conventional leaves a great deal of residue when burnt. A "Blend" is only marginally better than a full conventional. Ask an old engine builder what an engine looks like inside after running conventional or a blend VS a full syn. The oil mist and other contaminants that are evacuated through the PCV system are what bake onto the valves. With no fuel spray cooling and cleaning anymore, these bake onto the valve starting immediately when the engine is new. So, one of the best things all can do is run a good full synthetic oil and never the cheap dexos blend. Aside from that, only installing a emissions compliant closed system that separates and traps 95% plus of these contaminates from the PCV system will prevent most of this. There is always going to be some formation from the back-filling function of burnt gasses due to EGR emulation in the variable valve timing. Also, a small amount of oil that lubricates the valve guides enters, but that is very minor.

100% correct. The dangers of using these on GDI engines is being ignored as these companies that their core products are these cleaners are now facing possible extinction
as the public learns. They are all pushing like crazy now. Same with top tier fuels that used to be essential in keeping injectors clean and piston tops and combustion chambers clean are now useless. Watch the next Shell or Techron commercial on TV and how they claim to clean the engines internal parts (they do on port injection engines) and how most dealer service center push BG or similar for the profits$$.

Education is the best tool. Any further details or questions on anythong technical related to this and solutions. just ask.

1analguy

Jeez, this is even more trouble than owning a black car. Apparently, it's not worth the trouble owning a GDI. I do have one vehicle with GDI. Fortunately, it's a 2017 Volt. The engine never runs, so the GDI aspect shouldn't cause too much trouble...