GDI engines and valve buildup - fact or fiction?

Been reading a bit lately about goo building up on the back sides of the valves of GDI engines, most notably Hyundai. Since they are on my short list, I'd like to separate fact from fiction.

The gist I'm getting is that, because there is no fuel in the intake tract, the back sides of the valves aren't getting "washed" by fuel additives, and some engines have a lot of gunk on the valves.

The only place I can think of this gunk coming from is the PCV system... or am I missing something else? Aside from that, where else would/could it come from?

Also of note, Diesel engines have been using direct injection for years. Why is this not an issue with them?

Lots of years ago, it was common to remove the heads from an engine to "de-coke" them. Is this going to bring back that trend?

Also, if PCV blowby is the issue, why not use a simple oil catch can to solve the problem?

Discuss.

It's an issue on BMW 1/335i engines. BMW even sells a fitting to use crushed walnut shells to clean the valves and intake tract in the head. A BMW/MINI shop I know has been doing this for a while now.

And it has been an issue on ALH TDI's for ages. Personally, I'm on my 3rd intake manifold (time vs. money - I buy a new one - someday I'll clean the ones I have...). Some guys reprogram the ECU to reduce or stop the EGR from recirculating the hot exhaust which is part of what causes the TDI problems (hot exhaust + oily PCV gas = cokey sludge). I've seen pics of clogged intake manifolds that will amaze will how little air an engine actually needs to run.

One reason that engines should be able to do this is that they all need to be only burning 1qt/over 10k miles. So, theoretically, there isn't much oil in the intake.

How some engines get away with burning as much as they do is a mystery to me- as it's really hard to not have long term emissions problems.

As for the "catch can"- most engines have very effective systems that remove oil in the airstream of the PCV. Better than catch cans do.

Can't really help on the Hyundai, as I've not heard of any issues of it.

But I'm not a massive fan of DI.

I remember reading that Mazda had a unique way of reducing such a phenomenon with their sky active engine but I forget what it was. Maybe someone with a stronger memory can chime in.

My buddy is a BMW tech - he says that between the valve sludge buildup, turbo issues and emissions system gremlins, the GDI engines have been awesome for growing his business!

In reply to nderwater:

BMW have had carbon build up issues for as long as I've been part of the auto industry- I remember working on their engines as an intern in the 80's at Chevron. Their engine was used because of it's tendency to sludge up.

It's no surprise to me that BMW has issues.

I seem to remember reading it has something to do with using the VVT to put in a lot of overlap to eliminate the EGR valve. The exhaust and crankcase vapor form the gunk.

I've heard of issues on the new Ford Ecoboosts (like my '14 Fusion 2.0 Ecoboost). But I've also asked a service adviser at my local dealership, and he said he's seen no problems. So I don't know what to think.

I've thought of disconnecting the charge pipe and spraying some of that GDI cleaner from CRC down the throttle body at idle, but Ford released a TSB specifically saying not to do that as any removed deposits from the engine can flow through the exhaust manifold and into the turbocharger's impellers, damaging it.

The Skyactiv supposedly keeps the intake valve temp above 400 to keep this from happening (or lessen it or whatever).

I have a first-gen Skyactiv 3 and I was initially worried about this gunk buildup. But I'm approaching 40,000 miles now and have seen no ill effects. I guess I'm not sure how I would even tell if my valves were gunked up? I assume there would be some kind of mechanical indicator (like lower MPG?).

I guess my dad's Sonata might be affected, then.

I've heard of it being an issue for most everyone. use good gas and oil, change often. Add an extra oil catch can and cross your fingers. Note, these tings need to be done at day one, an abused 75k motor can only be helped by taking it apart....

Happens on all the fsi vws as well. I have two with 50-60k that looked like they were breathing oil.

I blame the egr via vvt on these... or blown crank case vacuum valves.

It's a problem on just about everything. It's not "the additives" in gasoline that keep the valves (relatively) clear, gasoline itself is a sufficient solvent. Yes, it's the PCV system causing it.

I've seen pictures of VW intake valves that were almost perfect negative copies of the ports.

Carbon in the chambers is also kind of a problem. On all of 'em. As is carbon-locking the injectors to the heads. One image that is burned into my mind was a 5000 mile old Ford Focus, front tires a foot off the ground, supported by a cherrypicker attached to one of the injectors...

I believe GM is trying to combat the intake valve coking problem by firing a short blurp of fuel during times of high reversion, to try to intentionally get fuel into the intake manifold.

Aside from that, we recommend intake style decarbonization every 15-20k on DI vehicles. I'll let you know how it works if I ever get a Mazdaspeed6... apparently on those it is easiest to just pop the intake manifold off and go to town manually. I'd want to pop the manifold off, visually inspect, put it together, then do a decarboning, then re-inspect to note the change.

For some reason, I don't want to do this to a customers' car. Da Boss has a direct-injected CTS but he doesn't seem to share the same mad scientist experimentation level of interest I have in the subject

I work at a Hyundai dealer, Its so common there are over 200 Elantra short blocks on back order across the US. I hear there is a dealer in NY somewhere that has 85 Elantra sitting on there lot waiting. Personally we buy bare blocks, and rebuild them. We recently did a Equus that had 32k on it, the intake valves were so bad im surprised it even ran, wish I got pics of it.

I have a 2009 GTI and they are known for carbon build up, I am at 78k and I am going to do a valve clean at 80k, most people do it at 40k

Well, crap. Guess that's one more thing to check on my truck....

In reply to Tom_Spangler:

It very much varies with engines. You may not have a problem.

Nothing an occasional "Italian tune up" won't fix.

iceracer wrote: Nothing an occasional "Italian tune up" won't fix.

Not really unless you can figure out a way to mist solvent into the air stream at WOT. Trust me, my TDI saw red-line treatment on a regular basis (at least once a day). Didn't really help.

iceracer wrote: Nothing an occasional "Italian tune up" won't fix.

Not really, no. If anything, that may make it worse over time, as increased crankcase blowby would be pumping more oil into the intake manifold.

SEAFOOOOOOOOAAAAMMMMMMMMMM

Hmmmmm, the FA20/4U-GSE - engine in FRS and BRZ uses direct injection as well as port injection... I wonder if this is a partial reason why they run both........

In reply to oldeskewltoy:

That was my thought when the operational theory was announced.

In reply to oldeskewltoy:

That's definitely a big reason why it's done that way, and I suspect they will all go that way eventually. Probably let them use an existing DI setup from some low power crapcan too.

Fueled by Caffeine wrote: SEAFOOOOOOOOAAAAMMMMMMMMMM

Not really its in the tank and out the injectors still no way to get it into the air stream on most cars without some rigging.

I have a feeling walnut blasting is the future for a lot of these cars

wearymicrobe wrote:

Fueled by Caffeine wrote: SEAFOOOOOOOOAAAAMMMMMMMMMM

Not really its in the tank and out the injectors still no way to get it into the air stream on most cars without some rigging. I have a feeling walnut blasting is the future for a lot of these cars

Running seafoam in with the air is pretty common too.

http://seafoamsales.com/sea-foam-through-the-air-intake/