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Thread: Intake Carbon Removal Using CRC GDI Valve Cleaner - Great Success!!

  1. #1
    Junior Member Dr.Evil's Avatar
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    Feb 2017
    United States / California
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    Lightbulb Intake Carbon Removal Using CRC GDI Valve Cleaner - Great Success!!

    Thought I'd share my experience with cleaning up my intake valves using CRC GDI valve cleaner. I don't know if the UK cars have the same EGR system as US cars, but I'm gonna leave this post here in case they do, or to help any other owners running into problems caused by carbon fouling in their x351 gasoline engine's intake. FWIW, it's the gunk from the EGR systems that creates the massive carbon buildup on the GDI engines. Most manufacturers have fixed this problem by installing an upstream injector in the intake tract to wash the valves like an old-school carbonated/throttle-body system. But for those of us with older GDI engines w/o this feature, this is an ongoing and serious problem.

    Here in the US the go-to solution for GDI engine carbon buildup has been walnut blasting (like sand blasting but using crushed walnut shells), but it's a fairly expensive operation because the intake manifold and associated bits have to come off first. Most shops here in California are charing somewhere between $500 and $700 for the procedure on a normally aspirated or turbo engine. And quite a bit more if they have to remove a super charger. So with that in mind, I figured I'd try a can of the CRC GDI cleaner first. It seems to be the new "hot ticket" on the forums I've searched. And since a can only runs about $12 here, I decided, why not give it a try. As an aside, I did look to see if it's available in the UK and it is, but holy hell, its £39.50 a can.

    I started this after researching the issues I'd been having with the gasoline V8 engine on my 2012 XJ w/ 60K miles on the clock, and found that they all seemed to point back to carbon fouling on the intake valves and injectors. Here's what was happening...

    • CEL illuminating and then turning off, with increasing frequency and on-duration over the last 10K miles
    • Trouble codes for MAF and MAP sensors being thrown when the CEL illuminates
    • Rough idle and very rough when revved in neutral, smoothing out around 4000 rpm
    • Intermittent engine shake when idling, getting worse over the last 10K
    • Low power and slight stumble under heavy acceleration

    This is a 2 person job, and you'll need about an hour and a half to get everything done since you have to shut off the engine and let it heat-soak for an hour after the application, and then take a short drive at highway speeds to finish the treatment. Here's what I did...

    • Warm up the engine by taking a short drive
    • Pop the hood and remove the plastic engine cover
    • Remove the bolt holding the plastic intake plumbing on the front, top left of the engine
    • Loosen the clamp on the intake duct at the front of the throttle body
    • Slide the intake duct back from the throttle body till it pops loose, and then slide it down about 1/8"
    • Slide the can's applicator straw between the intake duct and the top edge of the throttle body
    • Let the intake duct slide up agains the applicator, holding it in place (w/ about 1/4" of straw inside the throttle body)
    • Have a partner start the car and hold the engine at 2000 RPM
    • Start spraying, about 5 to 10 seconds at a time till the can is empty (it took me around 3 to 4 minutes)
    • Have your partner let the engine return to idle
    • Remove the spray tube and pop the intake duct back onto the throttle body
    • Have your partner rev the engine a couple of times to 3000 RPM and then shut it off
    • Make sure the intake duct is seated back on the throttle body and assemble in reverse order
    • Let the car sit for at least an hour so the engine can heat-soak
    • Hop in and go for a spirited drive at highway speeds for at least 10 minutes (ignore the white exhaust vapor on first startup)

    I honestly couldn't be happier with the results. I figured it might illicit a slight improvement and maybe get rid of the intermittent CEL. In fact, the CEL has now been permanently off for a few hundred miles. The engine idles and revs smoother than it has in at least a couple of years, and there is a considerable and very noticeable increase in power. All the carbon buildup related problems are gone. And true to the product reviews I've seen for this stuff, the results continued to improve for the first couple of hundred miles after the treatment. So two big Dr. Evil thumbs up for this stuff. I'm going to try some BG fuel system cleaner to see if I can get any additional crud out of the injectors, but my car is already running great so any improvement will just be icing on the cake, as it were.
    2012 XJ 5.0L V8, 2012 Mini Cooper S 6-speed Manual, 2014 Honda VFR 800 Interceptor - The details of my life are quite inconsequential

  2. #2
    Senior Member
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    May 2017
    Brackley, UK
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    Thanks you that, good to here real results, as I'm normally sceptical of these types of product.

    (Though as mine is a diesel, I won't be trying it)
    2010 XJ Portfolio running on lorry fuel. I know, Jag Diesel is just wrong!

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