Don't Skip the Additional Recommendations

Every week or two there’s a posting here about someone having their car in for scheduled 30K/60K/90K maintenence and being told the car should have some additional service done. The overwhelming response is that the customer do only what is outlined in the owner’s manual and nothing more. That seems especially true when it comes to fuel injection and intake cleaning.

I think it’s worthwhile to say that we (shops) know what we are doing and when I say your car should have a fuel injection and intake service every 30,000 miles it’s not padding the bill or selling snake oil. It’s keeping your car running normally.

This picture may not mean much to the average motorist, but to the people here who know what the inside of an engine should look like it may be interesting. There is obviously an abundance of carbon buildup and coking on the intake valves. If the customer had done the Induction and Fuel Injection service every 30K the intake and valves might not look like this at 86,000 miles.

Throwing a bottle of Techron in the tank certainly doesn’t hurt anything, but it does nothing to prevent a problem like this.

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If the cleaning solution doesn’t pass the valves… and on a DI engine it does not… it won’t prevent this!

Not the worst I’ve seen pictures of, but bad enough.

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In my experience I would say this is about normal for 90,000 with no preventive service.

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Do you typically chemical soak and scrape?

Or walnut shell blast? Or something else?

What kind of car is that?

We push the chemical intake cleaning at 30K for the cars like this one that need it to try and avoid manual cleaning later. We don’t have our own walnut shell blaster, there’s another shop nearby that we sublet that to. I believe the shell blasting is a better process than spray and scrape.

But in this case it’s irrelevant, the head is coming off. Kid ran the engine low on oil and jumped the timing chain. All those valves are now bent.

2011 Volkswagen 2.0

I don’t know if it would work in your situation better than shell or not or if you could even find one but years back when I was still trucking I picked up a load of pelletised dry ice that I didn’t even know that there was such a thing anyway it was going to a bakery and I had to ask about it they said they had a machine like a sandblaster that used the dry ice to clean the ovens and all the clean up they had to do was a wipe down with a towel.

Of course, I do not believe that professional mechanics who recommend top-engine cleaning on a modern vehicle are “padding the bill or selling snake oil”.

However, I would argue that any car which needs “fuel injection and intake cleaning” every 30,000 miles to avoid misfires and/or engine damage caused by carbon buildup is a piece of junk that I don’t want to own. How often was this service needed in the days of TBI or multiport fuel injection? (Hint: I have taken apart junkyard engines with hundreds of thousands of miles on them, and they looked much cleaner than this 86,000 mile example.)

All these “technological improvements” make the engines of the early 90’s look better every day. Back then, you only had two valves per cylinder, and adequate clearance was provided in case the timing belt should fail. Now, we have interference engines, with a hydraulic tensioner for the timing belt or timing chain…what could possibly go wrong with that idea?

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Quite true but… a modern turbocharged DOHC DI 2.0 liter 4 cylinder makes more horsepower and similar torque as that V8 but gets 2 times better fuel economy in a similar weight car. That is progress.

Edit: Many of those V8s had nylon timing gears. Failure would not bend valves… but replacement was required at about 30-35K miles.

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For DI engines maybe, for port injected or newer vehicles with both direct and port injection. I don’t think there’s a need to have the fuel system cleaned every 30k miles.

I wound-up ditching my '60 Ford Falcon when it was about 19 years old because its “fiber” timing gear failed, and the cost of tearing-down the engine to replace it exceeded the book value of the car. Because it had been a “Grandma car” that I had bought 2 years earlier, it only had about 25k miles on the odometer.

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Friend has a new qx50 with VC motor which has gdi and mpi. The spec sheet says it may use both in some conditions but it does not say it favors one over the other. Does it use gdi a majority of the time? For light cruising? The info is unclear.
Variable compression, variable turbo boost, variable gas injection, variable valve timing, variable ignition timing. Oof.

Is that from a DI engine? I haven’t owned a DI engine yet. But I’m very skeptical that this happens on non DI engines much. Since 1987 we’ve owned 5 vehicles with well over 300k miles and never ever had any Fuel Injection cleaning. Our current vehicles have over 150k miles and 240k miles and no Fuel Injection cleaning. And EVER EVER had any issue with fuel, performance or any other thing that carbon buildup could cause. I’m sure there’s probably some carbon buildup, but nothing like this.

And Toyota’s DI system is a hybrid system which will help prevent this type of problem. I think Ford does too.

A friend had a Ford pickup with the 302.

The plastic gear/timing chain failed.

Bent valves on both heads.


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Documents I’ve seen say MPI is used at light loads and GDI is used under high loads to cool the cylinder charge and reduce chance of knocking.

And on top of that it does all that with tailpipe emissions that are less than a third of what they were 30 years ago, so the air we all breathe is cleaner as well.


I will just say that I agree with asemaster completely.
As for the pic of the cylinder head shown that is not really a rare situation.

Seen it many times over the years with all types of makes and models and have spent many hours at the wire wheel knocking that crud off before performing a valve job.
Buildup like that can cause an otherwise great condition engine to idle slightly rough, stumble, etc as it disrupts the air flow.

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All of this convinces me that I’ll want a good long borescope to check out my intake tract if I get a DI engine.