Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

GDI Carbon Buildup

Recently you published a response regarding carbon in engines and the obsolescence of “Oklahoma” tune-ups. I own a shop in Sacramento CA and while I agree that for a long time carbon buildup was not a problem. But with the proliferation of GDI engines carbon has once again become a problem because we no longer have gasoline passing over and cleaning valves. In our experience hybrid vehicles like Prius models that turn off at stops also tend to have carbon build up issues. You would be doing me and my fellow shop owners a favor by informing vehicle owners of these situations – so when we tell them there car has carbon build up issues they will not think we are lying to them to sell them services they do not need. Owning and running an independent shop and gaining customer trust is very difficult under the best circumstances. Thanks for any clarification.

1 Like

We have no idea if Ray ever looks at this section of Car Talk and I have never seen a reply by him.
Your best move would to be find a good article of one page length and put it a frame in your waiting room . That would be an easy way to support what you tell a customer.

And mostly the forum members here agree with you on carbon buildup in direct injection engines.

1 Like

Ray sometimes addresses questions posed here originally, in his Dear Car Talk newspaper column. Yours is a interesting question, so suggest to keep an eye on that column OP in your local newspaper.

Thanks guys. I will post an article in my lobby and keep an eye out for any other repsonses


Yes, which is why I would NEVER buy, own, or accept as a gift any vehicle so equipped.

You may have to give up driving when they are all that is available. Others want cars without electronic assisted, like power windows, power door locks, or keyless entry. Those are rare, too. Some manufacturers reduce the problem by running hotter and burning more carbon off the valves during normal use. You might investigate which vehicles they are and limit future purchase decisions to them.

1 Like

Some manufacturers have also improved their piston ring seal so that there is less crankcase pressure. Some also have revised their evap systems to capture more oil vapor and remove it before it hits the intake.

It goes without saying that I DON’T want power windows/locks/seats, alarm, sunroof, touchscreens galore, or any of that other garbage. And you’re right that it’s getting very difficult to find anything so equipped with less than 200,000 miles and no major body damage/mechanical problems.

Now, I am starting to reconsider whether I should junk my 95 Caravan, which has a lot of features that I DO like, or put a lot of money into it to have it running well again. Next year, it will be 25 years old, and eligible for “historic vehicle” status.

1 Like

Yes. And in some engines, a portion of the injected fuel is directed at the intake valve when it’s open, helping to keep it washed.

You are in the minority since vehicles with those features are selling well. That makes them valuable features to the auto manufacturers. We bought a 2017 Accord with moder electronic assists, but not the safety suite. We also bought a 2019 Odyssey with the additional safety suite. So far I like the features in the van. Mrs JT went to the outlets early last week and ended up with a cracked windshield from a meteoroid. There was no traffic anywhere near her, so what else could it be? It’s more of a hassle to replace the windshield because the front facing camera has to be moved to the new windshield and then recalibrated. We got the windshield Friday and get the recal tomorrow. Still like the van, though.

BTW, it’s OK if you don’t like those features, and you can turn a lot of the money off. It does make the vehicle more expensive, but some of that is made up by reduced insurance costs. There are other things I where I’m in the minority and I know that they just won’t change to fit my desires, so I know what you mean.

I rented a 2019 Corolla couple months back, 2000 mile one week trip, and while I’ve complained about the keyless entry reliability and expense problems posted here, I was soon ignoring the key in the lock method and punching those buttons on the fob to open and close the doors and trunk , like I’d been doing it all my life … lol … I continue to prefer the manual windows though on my 28 year old Corolla, to the power windows on the 2019. I was constantly having trouble figuring out which button to press and which direction to press it to open and close the windows on the 2019. Given this button confusion & reliability problems power windows noted here, not enough bang for the buck. The other thing I noticed about the 2019 equipped w/automatic vs the 1992 equipped w/manual is the 92 is very noticeably quicker and nimbler in the 0-35 mph range, the steering is more responsive, the feel for the road is better, and generally the 92 is much more fun to drive than the 2019. Another problem with the 2019, visibility. Especially the massive A-pillar which was constantly blocking the view out the front windshield. I did like the back-up camera on the 2019, that’s a very good safety feature and makes backing up considerably easier. As for the other “advanced” features on the 2019 … meh …

1 Like

Only YOU would make those kind of comments :smiley_cat:

What could be easier than keyless entry . . . ?

Put the key fob in your pocket and keep it there

Walk up to the door and grab the exterior handle, at which point it unlocks and you’re already in the car. Step on the brake pedal, push the start button to fire up the engine

I have no response to that . . . :confused:

So you don’t value abs, stability control, air bags, and so forth . . . ?!

Maybe you should keep driving the 1992 Corolla and your F-150 until you quit driving

Newer vehicles are definitely not for you

by the way, I’m surprised you mentioned the model year of your Corolla. You hardly ever do that. You usually refer to it as an early 1990s Corolla . . . maybe you like to keep things mysterious?


Just curious about number of miles on average is a cleaning necessary, typical cost, and varience between models. Not sure if our Rav4 2017 has it. Throwing it into a maintenance plan my thought.

I can do the window buttons without looking. It’s as easy as pie.

Actually, the electric windows are pretty reliable. I never had problems with my Accord in the 12 years I owned it, nor did I have problems with my Silhouette over the 15 years I owned it. If there are problems with the power windows, they are likely to be with the mechanical parts of it.


The newer one is probably many hundreds of pounds heavier - and does any automatic give the same feel of control and connection that a simple 5 speed stick gives? I’ll hold onto my 1999 Civic 5 speed until they pull it from my cold…

Of course, the newer car is far less likely to result in death. It is a quandary.

1 Like

You can add my 94 Saturn, 01 Solara, 04 Carolla, 09 Focus, 05 T&C, 05 Odyssey to the list of cars that I’ve never had problem with power windows. Also the vehicle driven by my parents, grandparents, in-laws, and brother too…I don’t get the hysteria some people have about power window failures. Sure they happen, but they’re rare. And in my case in particular, the Focus, and two minivan have hauled around young children that enjoy raising and lowering the windows until I lock them…

I have replaced 3 power window regulators in my GM truck. It is so common, they are cheap and in-stock at all local auto stores. I can swap one out in 20 minutes. This is the only vehicle I’ve ever had this problem with, but it IS 15 years old.

Toyota has a valid solution for this problem by having both port and direction engine.At higher RPMs the engine is direct injection…th en at cruising the engine switches to port injection. This switch allows the cleaners in the gas to help prevent any carbon buildup. Ford is also big into this technology.

The electric windows in my 1981 Accord were trouble free out to 13 y.o.
In my 1985 Accord the drivers switches got flaky at about 10 y.o.
A spritz of contact cleaner fixed that.
The windows in my 1988 Accord started moving slow in the winter at about 15 y.o.
A little fresh grease on the regulators took care of the issue.
No issues with the windows in my 2006 Matrix over 12 years.
To me, being able to operate the back windows from the driver’s seat is a big plus.

Re the original topic, I haven’t seen much talk on the internet about engines having actual performance problems from IVD other than the earliest examples, mainly BMW’s and walnut blasting.
While some are spraying cleaners into the intake as often as every 10k miles I’d be concerned chunks of carbon finding their way to the cat converter.
I plan to leave it alone on my current GDI Hyundai for at least 50k miles if they’re no symptoms.