Carbon Buildup in Throttle Body
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    1. #1

      Carbon Buildup in Throttle Body

      AT 27K miles, my dealer told me our XC90 has excessive carbon buildup in the throttle body and needs an air filter. Quoted me $150! I can change the air filter in 10 minutes at the cost of $20-25, but wasn't sure what cleaning the throttle body entails? Is there somehting that can be used in the gas tank to clean this, or is this really going to take the dealer/mechanic to handle this?

      As a side note, they told me the front brake pads needed to be replaced. Quoted me $418 for pads & rotors! yeah sure. I think I have 5-10K miles left on them. I will replace the pads myself. Just thought I'd share


    2. #2

      Re: Carbon Buildup in Throttle Body (spideyman)

      The air filter is easy, but you must remove the MAF plug and hose from the airbox before removing the filter. Also, there is a "one time use only" nut that holds the bototm of the airbox in place, DO NOT MESS WITH IT. It is hard to get back on.

      I know there are special cleaners that the dealer uses for carbon buildup, you should be able to buy a can. I would give Brentwood Volvo in Missouri http://www.brentwoodvolvo.com a call. They are super helpful and can likely sell you the stuff cheap.

      As far as the brakes, I recently did my own and the parts are only ~160, for pads and new rotors.
      Here is my link for the how-to section...

      http://home.comcast.net/~toddhaddon/Volvoxc90.htm

      Todd


    3. #3

      Re: Carbon Buildup in Throttle Body (Colorado XC90 T6)

      Thanks Todd! I saw your superhelpful post of your brake job! It will definitely serve as a good reference for me! I will also give Brentwood a call about the cleaner.

      Thanks! -Mike


    4. #4
      Member Mr. P's Avatar
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      Re: Carbon Buildup in Throttle Body (Colorado XC90 T6)

      Nice job, Todd.

      Why did you replace the rotors? Were they out of spec, or did they pull to one side with your hands off the wheel?

      Unless it was one of the above, I would think they would last through numerous pad replacements.

      Mr. P

      2005 XC70 2.5 AWD, 2008 XC90 3.2 AWD, 1983 928S 5-speed, 1984 944, 1990 S2 Cabriolet, 1974 TVR 2500-M..

    5. #5

      Re: Carbon Buildup in Throttle Body (Mr. P)

      Quote, originally posted by Mr. P »
      ...Why did you replace the rotors?

      I debated this back and forth, but Volvo specifically told me that their rotors should not be turned.

      Different dealers seem to have their own opinion, but I had trouble finding anyone local who would even consider machinging a Volvo rotor. That said, I did not want to get the rotors off and not have a replacement set.

      I will probably have my old ones machined so that I have a "new set" ready for the next time. I just hope it is more than 15,000 miles from now


      Todd


    6. #6
      Member Mr. P's Avatar
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      Re: Carbon Buildup in Throttle Body (Colorado XC90 T6)

      I'd save the old set for sure, as they're probably perfectly suitable for running for years. There is no need to toss rotors just because you wore out some pads, in my opinion.

      I'm running the original rotors on a pristine Porsche 944 right now, and they have 165,000 miles on them, they're not scored, and they brake well enough to go to the track. The Volvo XC90 is generating a lot of heat when the brakes haul the vehicle down, but even the rears are vented, and they're huge. Personally, I doubt if I would have even considered changing out the rotor.

      Even in the past, when I have had scored rotors, the cheap fix was to insert a spare pad on that rotor, while changing out all the rest, and let the spare pad polish the score marks smooth (not erase them, just smooth things out) and then pop in the good pads. Unless a rotor is causing the vehicle to pull to one side or another, I don't think even scoring makes a difference, as the surface area on the rotor is still being gripped by the pad in a uniform manner.

      The prev owner of my 928 scored up the rear rotors pretty badly. The car would haul down nicely, very powerful brakes, but they looked bad. I changed them out and didn't notice any difference in the way the car brakes, but those drilled rotors look cool

      Ask a dealer if the rotors have to be turned every time you change pads, and they'll have to give you the liability management answer, but in reality, again in my opinion, lightly scored rotors can last many years and work fine IF you can still take your hands off the wheel and hit the brakes, and get a straight stop. Naturally, when the wear factor has them thinning out below spec, they should be replaced.

      Mr. P

      2005 XC70 2.5 AWD, 2008 XC90 3.2 AWD, 1983 928S 5-speed, 1984 944, 1990 S2 Cabriolet, 1974 TVR 2500-M..

    7. #7

      Re: Carbon Buildup in Throttle Body (spideyman)

      Quote, originally posted by spideyman »
      AT 27K miles, my dealer told me our XC90 has excessive carbon buildup in the throttle body

      Not to stir up an old debate, but have you only used premium fuel?

      Also, there are two schools of thought concerning throttle bottle cleaning.

      1. Spraying throttle body cleaner into the throttle body until the deposits are no longer visible, and then starting the engine and the white exhaust represents the deposits and cleaner being burned away. The throttle body is left in place during this cleaning.

      2. Remove throttle body first before cleaning because the deposition is so viscous that it may not be completely burned away and may deposit onto the valves and top of the pistons.

      #1 is OK for Teutonic sport machines , but always use method #2 with Volvo's.

      Some automobiles have more than one throttle body, but I'm not sure about the XC90. Ask your technician if he can show you the condition of your throttle body and judge for yourself. Also ask if it will be removed for cleaning. $100 is probably the going rate judging from previous quotes I've received on other automobiles.


    8. #8
      Member Mr. P's Avatar
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      Re: Carbon Buildup in Throttle Body (dachshund2)

      So how does carbon get on a throttle body that is upstream from the fuel injectors?

      Mr. P

      2005 XC70 2.5 AWD, 2008 XC90 3.2 AWD, 1983 928S 5-speed, 1984 944, 1990 S2 Cabriolet, 1974 TVR 2500-M..

    9. #9

      Re: Carbon Buildup in Throttle Body (Mr. P)

      The throttle body gets carbon deposits from engine gas recirculation. There is a return inlet that sends post combustion gases back into the intake and throttle body for emission monitoring reasons. This gas causes deposition to occur.

    10. #10

      Re: Carbon Buildup in Throttle Body (dachshund2)

      Does this apply to all Volvos? or just Turbo models?
      Thx!

    11. #11
      Member Mr. P's Avatar
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      Re: Carbon Buildup in Throttle Body (dachshund2)

      Quote, originally posted by dachshund2 »
      The throttle body gets carbon deposits from engine gas recirculation. There is a return inlet that sends post combustion gases back into the intake and throttle body for emission monitoring reasons. This gas causes deposition to occur.


      Thanks for the info, learned something new today. In using the "carb cleaner" type products, I've always been a little concerned about what happens to the cylinder walls when the stuff grinds it's way through the motor after squirting a lot of liquid into the system. I've used Techron for years to keep injectors and valves in good shape, but the throttle body system Volvo uses sounds like a maintenance issue waiting to happen, I'm glad to know it, so I can keep an eye on it.

      The comments about removal and cleaning sound better than letting all the "debris" and chemical solvent into the motor.

      Mr. P

      2005 XC70 2.5 AWD, 2008 XC90 3.2 AWD, 1983 928S 5-speed, 1984 944, 1990 S2 Cabriolet, 1974 TVR 2500-M..

    12. #12

      Re: Carbon Buildup in Throttle Body (024tnfi)

      Quote, originally posted by 024tnfi »
      Does this apply to all Volvos? or just Turbo models?
      Thx!

      Throttle bodies can be found in both turbocharged, supercharged, and normally aspirated engines.

      Here is some additional info about injection systems and throttle bodies.
      http://www.holley.com/HiOctn/T....html

      P.S. Spidey is it premium, mid-grade, or regular? Paper or Plastic ?


    13. #13

      Re: Carbon Buildup in Throttle Body (dachshund2)

      No, I always use mid-grade fuel. (and usually plastic! )