I have heard on other forums about a "Top End" carbon cleaning that can be done by the dealer. It involves solvent being introduced into the intake manifold, allowing it to soak, then running the motor to clean out carbon deposits. Does anyone have any info on this ? Good/bad results ? Cost ?

 

I’m very fuzzy on how to use this stuff.
The cleaner your talking about is a GM product.
But that doesn’t mean anything; it’s a very good product.
This was used more or less on carbureted engines, but can be done on EFI.
It says how to do it on the bottle, but here’s what I remember.
With the engine running pour the top end cleaner in the intake, just about till it stalls keep pouring it so the engine keeps wanting the stall, but don’t let it. The amount you pour in is fuzzy but I think 1/2 to 3/4 of the bottle.
after this you shut the engine off, and pour the rest of the cleaner down the intake, leave it sit, the start the engine and hold it at wide open throttle, black soot pours out the exhaust usually, its all the carbon from the engine.
Just hold it at redline till it’s clean, some mechanics even take it out on the road, and just stick the accelerator to the floor (severe beating).
Its fun.
If you've had this done to your car that’s probably what the mechanic did.

Oh and by the way this was done on a lot of cars that grannies and old people owned, the cars usually came in with a slight drivability problem, just needed the carbon cleaned out!!!! Hehehehe…..

 

I used to work at a GM dealership we did this alot to caddy's...
I would not recomend this on a normal running engine. Most cases it does nothing because there's nothing to clean. Plus you are supposed to take off your cat converter. Use a good fuel inj cleaner every 6 months or so... and you'll be fine.