Hey everyone, I have a 2014 Forester XT, and I've had to bring it in to Morrie's 3 times, because I kept getting a check engine light that was coming on. It was throwing the P300 (can't remember the exact number) code for random misfire. Finally, they told me that they needed to do a top engine cleaning, because it was building up too much carbon because the DIT's are notorious for that. Ended up being $149 for that to be done. I run Costco 92 through it, because it's a detergent gas. I was told by the dealer that I should run non-oxygenated gas through it once in a while, because it helps with carbon buildup? I'm not sure how I feel about that. Any thoughts? They also suggested that I have the top engine cleaning done every 30K miles...Seems excessive. Would running seafoam through it achieve the same effect? Has anyone else been running into this same issue?
Yeah, they did the top engine clean. Does that sound normal that they're going to need to keep doing it every 30k? Is there something that I can/should be doing to help mitigate this?
Look for the logo Top Tier and use different brand gas stations periodically. Each use different formulations of additives. One will clean what the other leaves behind.
Direct injection engines are notorious for carbon buildup on top of the intake valves no matter what gas or gas additives you use. The buildup often will occur due to the PCV system injecting oil/gas vapors on the intake side. In addition, with the hot engine cooling off, any additional vapors will collect on the relatively cool side of the intake valves. Also, from personal experience, the diy intake cleaners are not very effective on an older engine. Your experience may vary.
"Seafoaming" an intake is an experience that everybody should enjoy at least once in their life. It's hilarious. Not saying it'll be a fix for this situation, but might help?
This article lists Costco as a Top Tier brand. Also listed is BP which at 93 octane is a favorite for those engines requiring "premium". Funny thing is that I have never noticed any "Top Tier" branding at the BP station I frequent. https://www.consumerreports.org/car-maintenance/study-shows-top-tier-gasoline-worth-extra-price/ https://www.toptiergas.com/licensedbrands/
I understand the EGR system is also responsible for carbon build up. So then would a EGR delete and AOS pretty much eliminate the carbon build up problem?
Which gas you use won't matter because it doesn't touch the valves. So if you use seafoam don't run it through the gas tank or it was a waste.
No amount of top tier gas or detergents in the gas or Seafoam in your tank is going to help Direct Injection engines from developing carbon on the intake valves. This is because the gas is directly injected below the intake valves into the cylinder. It never touches the intake valves. This is a trait of ALL direct injection motors UNLESS the engine uses a hybrid fuel injection system consisting of direct AND port injection. In this application, the addition of a port injector will clean the valves by spraying fuel on them. The BRZ uses Toyota’s port/ direct injection......and the WRX should have used it too in my opinion. MANY BMW’s and Lexus models are even worse. Here are your options: 1.). Chemical cleaning. While the engine is running, spraying seafoam into the intake manifold through the MAP sensor position will wash the back of the intake valves. Also, CRC makes a spray specifically for this. How often? Who really knows. I would say every other oil change. 2.). Mechanical Cleaning. Using something like walnut shells and a media blaster to clean the valves and intake ports. Subaru makes and sells a kit for the former. The latter must be done at home or a shop offering the service. No Subaru shops offer this service. Also, it is time consuming and better be done right as walnut shells in the cylinders is obviously going to be disastrous. If you can find someone to do it, they will charge around $600. Auto manufacturers these days have turned to all kinds of aids to get even 1 more mpg but pass on the maintenance costs of the new (and rarely better from a maintenance or longevity standpoint) tech to consumers. Direct injection requires valve maintenance. Using thinner oil to reduce internal friction losses means more oil burning. CVT’s and 10 speed transmissions are still still unknowns for longevity and are nightmares to repair. Shortly, we will be longing for our “old” port injected motors and 5 speed autos or a manual transmissions.
Also, the EGR system (exhaust gas recirculation) is responsible for dumping the products into the intake manifold that cake the hot intake valves. Removing this system will require a tune and void your engine warranty but I have spoken to several people I trust that report an EGR delete along with an air/ oil separator virtually eliminate the carbon buildup in the intake valves. My car will be stock until the drivetrain warranty is kaput and then the TGV and EGR are coming out.
I had mine done when I bought it about 20k ago and I'm getting some serious signs of it all over again. Definitely a problem with these engines, which I'm sure Subaru will acknowledge in 12 years after every warranty is well past its expiration and the vehicles are on their 18th owners.
