For your information - Problem Caused By Carbon Buildup In Throttle Body

[88Racing]

Ran into a problem a few weeks back on my gmc work truck.

Why I am posting this message is to let people know about problems with wired throttle bodies. The tb before this one only had a position sensor and cable was on return spring.

Approximately 6-8 years ago auto mfg's decided the cable to the tb was not necessary any more and that allowed for more control of the management system. Slowly but surely all vehicles are going to this.

What the problem is carbon build up on the tb butterfly. This carbon problem pretty much found everywhere worldwide. The one problem I am describing is found in the upper colder states but it does affect everyone that drives in cold weather.

What happens is the vehicle is driven on a humid day(like when snow is melting 30-40 F)and then the dew point rises and temperature drops at night. The moist air in the intake tube will frost up and is more likely to form on the carbon buildup on the butterfly.

Okay so if the vehicle starts the tb will open to the default warm up setting and tb plate will get froze stuck and the drive motor will sense the extra resistance as motor warms up and force the CEL and limp home mode. This is the good scenario(what happened to me).

The bad scenario is the tb butterfly gets frozen shut. Maybe it will run and idle real rough or maybe will not start at all. Forces resistance on the drive motor turns on CEL and puts vehicle in limp mode.

The fix for the first scenario is just let it run awhile and shut off and the motor heat will thaw it out. Restart the vehicle you may have to do this 3 or 4 times to get CEL off.

The fix for the second take the air intake supply tube off and blow hot air in from a hair dryer(don't use the wifes) to thaw out(only use low setting)DO NOT USE OPEN FLAMES
Start 3 or 4 times to clear CEL.

(In most cases these steps will work unless something else is wrong)

In the end the carbon needs to be cleaned out of the tb. Take it out and do the cleaning on the bench. Why? Some of the solvents might start eating away @ the intake manifold(plastic) and or gaskets. Use only certified cleaners approved by the mfg's or hire a shop to do this.

This can start happening to any vehicle with more than 75K and or vehicles with a lot of idle time.

Tom our mechanic went out on over 15 of these calls one morning. Of course he has portable scan tool. But he found out I was on this forum and wanted me to spread the word.
Save the price of a tow truck.

Lars

This is just an example of my situation. Your situation may be different and if you have limited mechanical skills just call a shop or a tow truck. Newer tb's are expensive so be careful.

[Jackpine]

Good post, Lars. I wonder if you'd start to see the "rough idle" that Bill describes on the PHP website maybe a little before you started getting all these serious symptoms?

In any case, seems like a good reason to keep the throttle body clean.

(And I hope you don't mind, but I changed your title to more directly reflect the subject).

- Jack

[88Racing]

Thanks Jack,

Dixie designs thread actually started me thinking about this. So I put 2+2 together and think that this might be the reason they offered him this service.

So maybe getting the throttle body cleaned should be a general practice when ever spark plugs are done.

Yes my truck had rough idle problems and because intake gaskets were just replaced and the tb was over looked by Tom's tech. I got it cleaned for nothing and the tow call paid for.

Just a thought.

Lars