Another Maintenance Question

[gwilks98]

The dealership recommends Throddle body maint ($100) and fuel induction ($140) for my car.

I thought throttle body was part of the fuel induction.

If it's not, what's the difference and are both worth the money? (vs. doing it myself.)

[Daedalus]

Did they give any good reasons for the recommendation? Is the idle not right? Is the gas mileage below what it used to be? It seems a lot of shops recommend services like these simply because the work has high margins and because your car has xx,xxx miles on it. The TB cleaning probably involves spraying a cleaning solution into the intake with the car running and while working the butterfly valve to clean the areas around the plate and any idle ports/passages. The fuel induction service hooks up the fuel rail to a pressurized cannister of solvent and the car is run until the cannister is empty to clean any varnish build up in the injector tips. I think both services might benefit some cars, but probably have little or no value on most cars that they're performed on. They are easy, high-margin services.
I hear and read a lot about carbon buildup on intake valves and how important it is to keep them clean by performing these services and using the right gas. Build-up was an issue with carbureted cars, not so much with modern fuel injection and computer controls. I pulled the valves out of my engine with over 220,000 miles on it, and I put mostly Costco gas through the car over the last 45k. The valves had a little carbon build-up--just a very thin, rough coating. Nothing I would worry about. I soaked the valves in a couple brands of injector flushes and TB cleaners overnight. I put a few drops of each on the carboned cylinders too. None had any impact on the carbon build up on either that I could see. The carbon didn't dissolve, the fluids didn't seem any darker, and the coatings didn't seem any easier to chip off.
I've had mixed results with injector flushing (I have the pressure cannister device). I've seen my fuel mileage go up by 2-3 mpg, but only for a few tank-fulls, and then drop back down to the pre-cleaning values. I wonder if I subconsciously changed my driving habits after the test to go easier on the gas pedal. Pretty much the same results for the 3 cars I've done it on.
If there's nothing wrong with the car or the idle I would decline the offer.

[mechmike0034]

:stupid: Yeah, what he said...

Ask him to show you where your FACTORY maintenance schedule recommends these items.

For the injectors - a bottle of Chevron's Techron (available at Wal-Mart or almost any auto parts store) once or twice a year will do as much (if not more) as his flush will.

If you have a rough or "hunting" idle cleaning the throttle body may help, but I wouldn't worry with it if it runs OK...