Removing carbon deposits from engine with engine still assembled - I got it now.
I don’t have an answer on that except for some theories.
These may work – I don’t have an answer on if they do, or not.
1 - drive the car like you stole it – to prevent carbon deposits to build-up from hard usage.
2 - pour a substance into engine while engine is running. Back in the early ‘80’s, a fellow technician insisted that revving the engine up to 3000 RPM then pouring ATF (Automatic Transmission Fluid) down carburetor will get rid of carbon deposits. I have no idea or proof that it does – but it does eliminate anyone else from the area for a spell, sense it produces a thick white smoke. Note: only performed with cars without catalytic converters or had cat’s removed for this
3 - use of walnut shells when engine is dissembled/partially dissembled. Soft enough not to damage anything but carbon.
Again – I have not tried any of the latter two versions, nor do I have any before / after pictures to know what works or don’t work. Even though I was a Chrysler tech for many a year, I didn’t do many engine repairs for them (except for my own “stuff”)
I do know that carbon deposits on piston tops, is what causes an after-run condition (after engine is turned off, engine will kick, sputter and will keep running for a short term – from carbon being hot enough to ignite fuel.
Note: I don’t recommend pouring much of anything down the carburetor (ATF, any kind of water or fuel) for a couple of reasons.
First is it doesn’t take much to hydro lock an engine. If you have enough liquid in a cylinder while piston is moving – then SOMETHING IS GOING TO BREAK!
Second reason is where is the carbon deposits going to go? Into the catalytic converter(s) – which stops them up.
Pickup coils do go bad – either totally dead or only go bad after a heat soak. Primarily at location of red arrow. The problem is it is hard to get pinpoint tests done to it due to its location – when/while car is acting up.
It is the cheaper item to replace (than computer) and does have a good percentage chance of being the problem.
It if was replaced and still doing the same thing, then the two other items are suspect (computer or fuel line vapor lock).
BudW