vettman96

Is there any issue known with deposit buildup on the back side of the intake valves due to not having a port injection system?
I have read about possible issues but have seen nothing definitive as it would apply to the LT1 powerplant.

Is GM aware of, and if so do they have any plans for correction with the intake valve coking issue present in the direct injection platforms as a result of the PCV system. Many members of the community are seeing an excessive amount of oil and carbon deposit buildup on the intake valves after only 5,000-10,000 miles and worse with even higher mileage engines on the C7. While I understand the purpose of the PCV system as it relates to emissions, with the introduction of direct injection there is no longer a cleaning process in place that would be naturally present such as from a port injection system. ( I extracted this addition per request).

FYREANT

I assume you are asking what GM plans to do about the evident direct injection oil "coking" issue. if that is the case, I am fully on-board with this being the next question that deserves an answer. I would consider asking the question like this though:

Tadge,

Is GM aware of, and if so do they have any plans for correction with the intake valve coking issue present in the direct injection platforms as a result of the PCV system. Many members of the community are seeing an excessive amount of oil and carbon deposit buildup on the intake valves after only 5,000-10,000 miles and worse with even higher mileage engines on the C7. While I understand the purpose of the PCV system as it relates to emissions, with the introduction of direct injection there is no longer a cleaning process in place that would be naturally present such as from a port injection system. This issue may be caused by several factors, possibly excessive blow-by from engine blocks with cylinders "out-of-round" (as several shops aftermarket companies have confirmed already) or dealerships that may be overfilling the oil during routine maintenance. I personally have an alarming amount of buildup after only 22,000 miles and I do not have a dry sump configuration which I understand makes the issue even more evident. Many members are installing aftermarket "Oil catch cans" as a makeshift solution to this growing concern. Are any alternative solutions being considered such as a factory installed vacuum pump for future models that may be able to regulate the amount of crankcase vacuum/pressure or a way to control the amount of engine oil that is being pushed back in to the intake system? If there are no current plans at future technology to resolve this issue, would GM consider offering an intake valve cleaning under warranty or through a technical service bulletin at certain mileage intervals to restore the fuel economy and performance lost due to this evident problem?

Thanks,

Anthony

atljar

This isn't just a GM issue, many other manufactures have the same issue with carbon buildup. Most of them are using a walnut blasting service to clean out the gunk while leaving the cylinder heads on the car. Interested in his response!

jvp

This question was added to the poll for the week ending 13 February. Vote here!

FYREANT

well, now that the Z06 track temp question has been asked, maybe we can get this one on the poll for upcoming week since it was second in line?

FYREANT

This should have been re-added to the poll for this week..

Perhaps next weeks poll then?

jvp

Yeah, it looks like this one got kinda lost in the shuffle. Keep it discussed and we'll poll it up next week. But there are some other really good C7 questions that have popped up recently, too.

jvp

Added to the poll!

FYREANT

I am really curious to see what GM/Tadge has to say about this. While this is a widespread issue with more than just Vette's or Chevy, that doesn't mean that an answer to the issue doesn't exist. Maybe it is as simple as adding a vacuum pump to regulate the PCV. Either way, IMO the current state of the coking issue is unacceptable. C'mon GM! This is your flagship car!

FYREANT

Can we get this one back in the poll this week by chance?

joshvetteg

Very interested in this!

FYREANT

I wish there was more interest in this question. Maybe now that some of the higher profile questions have already been asked this one will get some attention again

CPhelps

It's definitely an interesting question. Early on when we heard the LT1 would be DI, we heard they redesigned the PVC system to be so effective as to prevent the oil coking. I don't know that I've seen any reports of LT1s with the issue yet, but as you mentioned, there are definitely reports of oil in the intake and full catch cans...

BigVette427

I definitely find the DI and carbon build up issue very interesting, especially now that Corvette has gone into the DI world. VW and BMW have been doing DI for awhile now and it's an issue there, as well.

I'd like to know if the auto manufacturer's really believe that the "solution" is just an intake and/or cylinder head cleaning once, twice, or more before you reach 100,000 miles, as if some sort of new scheduled maintenance procedure. If that's the case, I'm really not interested in DI on a street car.

\Boost Monkey/

This is a great question.

Should definetly win this round hands down. At least it better.

I am not new to DI cars and my past FI euros coke like SOBs... Although it's not a huge deal for me getting walnut blasting every 35/40k for about $350 a pop, it just blows my mind that not one manufacturer has developed a good solution for this.

The newest offender on the block is Ford's Eco-boost lineup.

FYREANT

Sure hope so. I am excited at how the voting going this week so far. I am curios though if this question is selected to send to Tadge, would we send just the inital question that Vettman96 posted, or possibly my response to his inital question, or maybe even a combination of both?

jvp

We'll send him what's in the initial post. If the OP wants to edit that and change his wording or what have you, he's more than welcome to do so before Sunday morning. If you think that it's important to do that, feel free to PM him and suggest it.

FYREANT

Thank you, I have messaged him about it since I feel it is critical to include some of the directly related questions and points I mentioned about this topic.

jvp

This question has won the poll, but due to the GM office shutdown (for 2 weeks), I won't be sending it to Tadge until after he returns. I've put it up as "Asked"; just know that it hasn't been sent yet.

09_BSM_Z51

I had a furd ecoboost. It was the main reason got rid of it for the ls3 corvette. I hope GM has a real remedy. I had never seen the amount of soot on a catted exhaust as I had with the 3.5tt whacko-boost. Absolutely ridiculous. I'm pretty sure my catless 13B rotary RX7 had a cleaner looking exhaust system than my f150 and the rotary ran really rich.