I hate creating a new thread to ask this and hope I dont get flamed. Searching brought me to so many results that neither of them seemed to answer the question at first glance. Anyway, regarding the need to redline from time to time to clean carbon, I was wondering, would redlining in neutral be harmful? I know most people recommend redlining under load and driving, for example, pulling 2nd gear to get on the highway. But from time to time when I pull into my garage and I had a rather calm driving day, I will pump the gas a few times and redline before i get ready to shut the car off. Thoughts?

 

it wont be harmful but it will have less effect than a good 2nd gear pull. to clean out the engine you need to open her up means staying on the gas and high rpm longer.
revving in neutral it only takes less than a second for the engine to hit rev limiter.
I wouldn't rev and shut off the car because it dumps too much gas into the cat which would ruin it quickly.

 

Yea thats what I figured, thanks for the heads up. I will probably stop wasting my time doing, probably just pissing away gas instead of doing any sort of cleaning.

 

Yeah - I can't see that being very effective at clearing carbon , not to mention that i wouldn't think free revving is a very good idea for the engine internals in general .

 

How's that?

You rev it up and then let off the throttle. PCM cuts fuel on 100% deceleration/0% throttle, until a preset point around 1500 where the fuel injection picks back up to keep the car idling. No fuel goes into cat during decel.

You rev it up and shut off the key. PCM loses power, cuts fuel, no fuel goes into cat during decel.

 

^^^ Thats kinda what I was thinking.

As far as trying to clear out carbon ehh... You always want the engine on load to help clear out carbon. There's a big argument over premix on what it does. I premix because I believe (and from what I've read) helps lubricate the seals blah blah blah... But it does help keep carbon from sticking from the Aux ports and the exhaust ports, overall it helps lubricate the seals and keeps carbon from sticking, it's a win win in my eyes.

 

Whenever i shut off my car i give it a little blip then shut off. I rev to 4000 rpm and as the rpms drop i shut off the car. I thought this was okay ?? Been doing this for a while and hasnt caused any problems ...

 

^^ I only do that if I had a half assed drive to the corner store just because it was the old school way of not flooding the engine.

 

^ I always do it even if the engine is warm. Just to be safe i guess lol.