For what I see coming through our shop, most GM DI engines that need intake valve deposit cleaning are cars that see a lot of city driving that do not get flogged by their owners. Mostly SUVs.
Typical concern is cold start running rough, sometimes enough to set a P0300 DTC but sometimes not.
Mileage can be anywhere from 20K to 60K.
Fuel plays a big factor in this as well. Some customers never have an issue and they use top tier fuel, actually go WOT every now and then and use a good oil and change it frequently.

I rarely see V series cars have carbon issues but that does not mean they are immune.

GM makes the best top engine clean hands down(I doubt they make it). I have had Porsche technicians come buy the stuff from us when they started having carbon buildup issues over 10 years ago. Never needed to use walnut shell blasting just a good atomizer for the cleaning fluid.
Key is to let it soak in and then WOT to clean out the broken up carbon.

If you arent having any driveability issues, I would not worry about it.
I am neurotic about my cars so they get a good top engine clean every 30K regardless.
On my V I am doing top engine clean and spark plugs at 35K to give me a clean slate since it is new to me and I want a good baseline dyno run.



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GM makes the best top engine clean hands down(I doubt they make it). I have had Porsche technicians come buy the stuff from us when they started having carbon buildup issues over 10 years ago. Never needed to use walnut shell blasting just a good atomizer for the cleaning fluid.
Key is to let it soak in and then WOT to clean out the broken up carbon.

If you arent having any driveability issues, I would not worry about it.

No driveability issues and I autocross on a regular basis so WOT is no issue. Can you speak more about the GM top end cleaner, p/n, cost, whether a moderately capable backyard doofus like me can use it successfully, etc.? Or is it best done by the dealer or other shop?

Thanks.

 

Some great info there. Top tier fuel is the only fuel to use with a direct injected engine. Just curious, where is your shop if you don't mind my asking?

 

Some great info there. Top tier fuel is the only fuel to use with a direct injected engine. Just curious, where is your shop if you don't mind my asking?

I am in the greater Seattle area.

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There is a thread in the forum CTS Vsport General Discussion - Walnut Blasting The Intake Valves. It has photos of LF3 intake valve back sides at 140K. That should give you an idea of what to expect with the LF4.

Walnut blasting the intake valves

Number 2 before & after, I’ll probably finish the other 5 ports tomorrow. 140K miles on my 2014. I’ve had the GM induction cleaning performed and around every 20K miles I sprayed a can of cleaner (Seafoam, MOC, CRC,) through the vacuum lines. All the valves look at least as gunked-up as these.

www.cadillacforums.com

 

The bulletin GM has put out for this topic is #16-NA-383. It outlines the symptoms, cause and procedures to correct the carbon issue. Pretty generic information, not specific to the LF4.

Part number for the top engine cleaner is #19355198. There is a fuel system treatment listed in that bulletin to add to the tank but if you are using good gasoline, you should not need it.

If you are mechanically inclined, go for it. If not, find a dealer or shop you trust, one that maybe you can talk to a technician about the procedure. This is not a guide by any means but here are a few key points and tips I can offer after doing this many times on many different engines. If you don't feel comfortable, best to pay someone who is experienced to do it.

Since the LF4 throttle body is not accessible, the atomizer that GM calls out can't be used. Intake manifold vacuum line for the PCV circuit is what I have used before. The bottle GM sells is large, you only need about 1/2 of it for a good cleaning, save the other half for next time.

Use gloves. This stuff is nasty. Fender covers are a must.

You want to use a rubber hose to induce the cleaner while holding engine RPMs around 2500, the engine will bog down as the cleaner is introduced and will run poorly, flash the MIL and smoke pretty bad. Do it outside. You want to be able to meter the cleaner as you do this, usually I will just pinch off the hose I am using to limit the amount of cleaner. You don't want to let the engine RPMs drop too low and allow the engine to stall, you can damage the engine if you allow it to hydro-lock.

Something really important is to get the engine really hot beforehand. This will soften the carbon up allowing the cleaner to work better. Once you have induced the cleaner, shut the engine down. Let the engine sit for 2 hours. Any much longer and the carbon will harden back up. Start it up, it will be a smoke show. If the engine does not start up or starts and stalls, there is still too much cleaner in the combustion chambers and you may have to let it sit longer to allow some to bleed past the rings or pull spark plugs to turn over the engine(not easy on LF4).

Next step is also really important. You need to drive it and drive it hard. Find a spot you can do about 10 WOT 2nd gear pulls to redline. This will blow all the carbon out of the engine that has loosened up.

Then change your oil and filter. This stuff gets past the rings and its best to dump the oil.

Cost for the whole procedure will be dependent on shop rate. Labor time is 1-2 hours, the cleaner I think is around $35 but it may have changed price.

Hope this helps!

 

When I had my intake off last at about 20K miles the intake valves and intake ports looked quite good with only a tiny bit of buildup where the stem meets the head of the valve. I do run catch cans for the PCV system though, so that may be helping as the one for the primary PCV line does catch a decent amount of condensation and oil crap that would otherwise be sucked through the intake manifold.

As far as removing any carbon from the intake valves and ports-- GM Top engine cleaner is fantastic stuff for sure, as long as it's used correctly.

As mentioned, the only place to really add it on these cars is into the PCV line that runs between the driver's side valve cover and the front of the lower intake manifold (which is connected to the lower intake below the throttle body) and let engine vacuum pull it in. Either have a helper hold the engine at 2500rpm or so, or if you have GDS2 manually command the engine speed to 2500rpm, then let engine vacuum draw it in slowly so you don't risk hydrolocking the engine.

Introducing the Top engine cleaner using the atomizer nozzle tool directly into the throttle body is the best way to do it and will distribute the cleaner more evenly compared to sucking it in via the PCV line-- but since the throttle body is inside the upper intake on these cars using the atomizer nozzle tool really isn't an option. I suppose if you really wanted to make this part of your maintenance routine you could drill and tap an 1/8" NPT port into the upper intake manifold directly above the throttle body, screw a water/methanol injection nozzle into the port you just drilled and tapped, spray the TOP engine cleaner directly into the throttle body via that nozzle, and then when finished remove the nozzle and screw an 1/8" NPT pipe plug back into that hole until the next time.

As mentioned by the poster above, only do the Top engine cleaner routine right before you plan changing oil, be ready for a smokeshow when you restart it, and change oil afterwards.

If it the valves ever do get carboned up extremely badly and TOP engine cleaner won't cut it, pulling the intake manifold really isn't hard on these cars-- especially since you can just flip the upper intake forward and set it on the radiator without having to drain the intercooler. The way the cylinder heads and intake ports are designed there is excellent access to the intake valves for media blasting. A harbor freight media blaster and a shop vac will make quick work of it, especially if you 3D print your own or buy one of the 3D printed intake port media blasting adapters to connect the shop vac hose to-- those really cut down on the mess.

 

I clean my valves with a gallon or so of methanol, each tank/month at a time (ZZP's AEM kit, which I got for the sole purpose of supplement & hygiene, not as a power-adder)
Along with Ethanol blend for the fuel injectors (I run E60%) ...I'd say that's a decent buildup-prevention setup!

 

Water / methanol is indeed an excellent intake valve and combustion chamber decarbonizer, and since that cleaning is performed every time you stick your foot in it, you'll be far more likely to follow that "maintenance schedule."

 

I read 16-NA-383. A question for both "tta1456" and "hunterdsylvester":

When you "pour in" PN 19355198, are you sticking a funnel in the PCV somewhere?

 

On a car that has no access to the throttle body, I find the most accessible vacuum line from the intake and use a rubber hose to suck the cleaner straight from the bottle. I meter it as it is drawn into the intake manifold.

PCV or brake booster vacuum hose works great on most cars.

If I can get to the throttle body then I have the atomizer setup that clips on the throttle and sprays it just in front of the throttle. Works great as it doesn't allow you to induce too much cleaner at a time but its more a technician tool than a home garage guy set up.

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Thanks for all the great info here! Makes me feel a lot better knowing the ins and outs of all this.

 

I would use the PCV line that runs from the front of the driver's valve cover to the center front of the lower intake plenum (it runs under the intercooler water manifold, but is easy to access.) That PCV line has quick disconnect tabs at each end so it's very easy to remove. Remove the PCV line and slide a flexible hose over the barb fitting on the intake (3/8" hose) and then dunk that hose into the TOP engine cleaner container. Pinch the hose going to the TOP engine cleaner closed and start the engine and bring the RPM up to 2500ish. Then slightly release your squeeze on the hose to regulate the flow (or put a 1/4 turn ball valve inline so you can regulate the flow) and engine vacuum will draw the TOP engine cleaner into the intake. Don't introduce it fast enough to let the engine stall or risk hydrolocking the engine, but let it in fast enough so the engine runs fairly rough. The engine will NOT be happy while ingesting the TOP engine cleaner and will probably throw some misfire codes and possibly a MAF related code during the procedure.

Only reason I wouldn't use the brake booster hose on these cars is because when the vacuum sensor at the brake booster detects a drop in vacuum the ECM will cycle the auxiliary electric vacuum pump. If the vacuum pump cycles during this procedure or any residual TOP engine cleaner remains in the lines afterwards there's a chance the auxiliary vacuum pump might suck some in since the vacuum line to the brake booster has a tee in it to connect to both the lower intake and the aux vacuum pump. TOP engine cleaner going through the electric pump probably won't do it any favors, and a new pump is about $120.

 

Ya on these cars the PVC hose is best. Brake booster hose is more an old school method on something with no electric vacuum pump.

The attached picture is the atomizer tool we use to spray in front of the throttle body.

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Thought I would add an update to this thread and some pictures of my engine.

I decided to replace spark plugs and clean the intake valves of my V this past weekend to give myself a clean slate before I strap it to the dyno and get some baseline numbers.

Attached are pictures of the charge air cooler manifold, intake and throttle body. My car has 36,XXX miles on it and there was no visible oil on the intercoolers, intake or throttle body.

I was actually surprised because anytime we have the charge air cooler covers off the CTS V's, there is usually some amount of oil coating the inside of the manifold.

Shows the oil air seperators built into the PCV intake tubes and the valve covers do a pretty good job! Still going to build a catch can set up but it is nice to see a well built PCV system.

I attached a picture of one set of intake valves to show the buildup I have on my engine. Not a huge amount but there is some for sure. Looking at the cylinder head ports, most have some dark carbon staining from the valves halfway up the port. Makes me think our engines may have most of our carbon build up from valve overlap during cold starts instead of oil ingestion into the intake from PCV gas.

Also got a pic of the AC Delco Top Engine clean I used to soak the intake valves.

Spark plugs looked good, gapped a new set tight at .028" and will see what baseline number I can put down.

Hope those shows some people what the insides look like and where a 36K mile car is at. Previous owner did not abuse but wasn't as anal as I am so should be a good representation of typical build up.

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Do you have any "after" photos of the intake valve cleaning? Did you just use the GM Solvent or did you also walnut blast them? Thanks.

 

Do you have any "after" photos of the intake valve cleaning? Did you just use the GM Solvent or did you also walnut blast them? Thanks.

I will shoot some this weekend, I ran out of time and had to get back home in a hurry so I just put it all back together quickly.

No walnut blasting, just the GM cleaner which is really good to clean carbon.

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Good pics.

Good point on a lot of the port/valve contamination possibly originating during valve overlap since the contamination primarily shows 1/2 way up the intake port.

That being said, the catch can on my car running between the DS valve cover and lower intake manifold (primary PCV flowpath when the engine is operating under light throttle / vacuum conditions) does catch a decent amount of both oil and moisture, I don't think valve overlap is the only source of contamination. The primary PCV path may only be a small contributor to intake valve "gunk" though, if it was a large contributor I'd expect to see more staining of the lower intake, starting where the PCV line connects at the front of the lower intake.

The intake valves on my car at 20K miles were substantially cleaner than yours with only a small amount of carbon, and the catch cans have been on my car since about 1000 miles.

The good news is the intercooler blocks, upper intake, and throttle body being clean means the factory air/oil separators for the crankcase vapor flowpath under boost (from both DS and PS valve covers to the DS and PS intake ducts on the inlet side of the turbos) are doing their job well.

One caution when doing this job... be very, very careful with the gaskets between the lower and upper intake manifold halves. They're only sold as a kit, and that gasket kit is over $400! WTF, GM...

 

Yes, I am glad the intercooler bricks were oil free.

Ya, catch can is for sure needed but it is a pretty good system for an OEM.


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It dawned on me that I never asked why the fuel and/or occasional use of methanol would make a difference if it's not being sprayed on the intake valves. How would this make any difference if the fuel never touches the intake side of the valve?

 

Most people running water/methanol on these cars are injecting it into the upper intake, often into the pipes that connect the upper intake to the turbos since that's the most convenient spot.

This means the water/methanol travels through the intake and hits the back side of the valves. Between the methanol acting as a solvent and the water "steam cleaning" the intake valves as it vaporizes, it works very well as a de-carboninzer for both the valves and combustion chamber.

I run water/methanol injection on one of my other cars, and last time I had the engine apart the intake valves and piston crowns were amazingly clean.

 

FWIW, many WW-II and later aircraft gasoline reciprocating engines used water injection to slow down the fuel burn (sort of an octane increase) and thus prevent detonation at high supercharger/power demands. The piston crowns stayed squeaky clean.

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Yes, higher octane fuels "burn slower" in order to allow a bit of additional ignition advance to keep maximum cylinder pressure in the best arc of the power downstroke for slightly longer time periods.

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Ok, so use of meth or water injection would be useful but what about those of us who don't? Why does the use of tier 1 fuel make a difference?

And I'm aware of both the water injection and high octane issues.

 

Top Tier fuels contain the correct amount of detergent in them to keep intake valves, injectors and combustiom chambers clean.
Valve overlap is the issue here with a direct injected car as thats the only way you get fuel or fuel components into the intake port and onto the back of the valve.



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Meth or meth/water may not do as good a job at cleaning the valves as we had hoped. Even after running top tier gas and putting a healthy does of meth (750ml/min) through the charge pipes, a friend of mine found his valves pretty gunked up when his heads came off. I'm coming up on roughly 2 years of 51/49, then 100% meth, and now 87.5/12.5 meth/water and I've got what I think is a noisy/sticking exhaust valve on the driver side, so my heads are coming off soon also. I'm interested to see how clean my valves are. I recently had a top end clean done by the dealership to try and get rid of the ticking, but it wasn't effective.

I'm going to ask the shop to send me pics of that they find when it happens, I'll post them here. I'm interested to see how much the meth really cleans off.

As others have noted, one caveat of GDI is that it injects fuel below the valve, so all those detergents in the top tier gas don't wash over the top of the valves to clean them.