Mike's LS3

GM has an effective carbon cleaning chemical that is directly injected into the spark plug holes. Let it sit, then start it up and watch the white smoke pour out of the exhaust melting away the carbon build up.
I am not sure if it is available over the counter.

jft69z

It's available over the counter at the dealer or online. Part number is 1052626. Was part number 1050002.

You can also spray it in a vacuum line, throttle body, PCV hose, brake booster hose etc. while running to get the intake valves too. They tend to carbon up pretty bad sometimes and cause a lean misfire when cold, the carbon acts like a sponge for the fuel.

For reference only:

rio95

This issue could be a little more obvious here. It sounds like you're running a stock tune. Do you know for sure that a vararam doesn't require a tune. I would bet that it does require some mad tweaking and it most certainly would require some VE tuning. Couple that with crappy 91 octane and this knock doesn't seem too surprising.

I ran a bottle of seafoam through my intake to clean the carbon buildup I found with a bore scope. Not sure it was necessary though because my KR problem ended up being the alternator.

Mike's LS3

Actually, GM #88861803 which can be used several ways, (not in the gas tank). They used it to presoak the carbon on the pistons through spark plug holes, let it sit for about an hour, then sucked it out before starting the engine. Also, available on amazon.

jft69z

I gave him the aerosol version of the top engine cleaner. The part number you listed requires an extra tool such as the OTC 7448A to inject the cleaner into the engine. Didn't figure he would want to spend around $150 to get the tool. (I use the 88861803 & OTC 7448A in my shop, works great!).



http://sandyblogs.com/techlink/?p=6659

Mike's LS3

How effective is the aerosol vs injectable w/tool ?

jft69z

I've used both over the years, good results either way. More cost effective to get the 88861803 at around $22...IF you already have the OTC type pressurized canister.

Keep in mind, there are 2 ways to use that canister.

1) for injector cleaning where you attach it to the fuel rail and run the cleaner thru the injectors (disabling the fuel pump and closing off the return line so none of the cleaner gets back to the fuel tank). The engine is running off the pressurized canister. Side note-the canister is nice to have if someone drops the vehicle off with a flatbed because of a dead fuel pump. I've used the canister to get the car running so I could get it into the shop so I didn't have to push it...uphill...by myself.

2) Attach the pressurized canister to a vacuum port, brake booster line, throttle body port, etc and run the cleaner thru the entire intake tract for a de-carboning procedure. It's best if you have the proper de-carbon adapters or throttle bore spray nozzle to use this procedure. You have to be more careful with this method so you don't add the cleaner at such a fast rate that you hydro-lock the engine. With the spray can there is a much less risk of that happening. I can either post or send you the procedure for this method if you need it.

It's recommended you change your oil & filter after doing a de-carbon as some of the chemical will seep down into the oil pan after the couple hour soak.


Plenty of reading here about carbon deposits (GDI engines are even worse for carbon deposits):

https://www.motor.com/magazinepdfs/052008_09.pdf

http://www.searchautoparts.com/motor...-carbon-issues

https://www.motor.com/magazinepdfs/122014_7.pdf

tblu92

You have to realize That IAT temps are supposed to read outside air intake temps---
Although you may be testing on a day that you deem is at 48* outside temperature THAT is NOT what the ECM is reading as IAT temp----The IAT temp sensor is located underhood on the air intake tube--- This location will always read higher IAT temps then the actual outside temp----Reason being the air tube will get heat soaked very quickly even in it is only 60* outside and can read as high as 140*
The only way to know for sure is to data log your car with HP or EFILIVE--and NOT on a dyno because a dyno will give you false IAT readings but by driving it on the street somewhere safe where you can run it at WOT up thru the 2-3 shift
THIS is your actual IAT recording----Not uncommon on a 70* day to have IAT readings of 130*
So to correct these false readings you need to desensitize the IAT timing deducts this ia not cut and dried---It is a trial and error process At 130* the ECM can revmove anywhere from 5-9 degrees of timing !!! and on a LS engine that msy work best at only 20* at WOT removing 9* would make it a lazy turd-----

BlindSpot

You have to realize That IAT temps are supposed to read outside air intake temps---
This is not true. IATs are measured inside the intake charge tube at the MAF on an E38, so the air has long since left the outside air environment.

THIS is your actual IAT recording----Not uncommon on a 70* day to have IAT readings of 130*
This is a generalization. You cannot assume these numbers will be true/accurate on different air intake systems and different designs and in different geographies such as altitude, moisture, air density and RPM. For example, I've never seen IATs 130* when the air temps are at 70*, but then the volume and speed of the charge coming in at my IAT are quite different than a stock NA LS3 with a stock AF.

So to correct these false readings you need to desensitize the IAT timing deducts this ia not cut and dried---It is a trial and error process At 130* the ECM can revmove anywhere from 5-9 degrees of timing !!! and on a LS engine that msy work best at only 20* at WOT removing 9* would make it a lazy turd
True and I agree it's a trial and error effort and I also agree you'll get better results in an actual drive environment for that day and that temp, over a dyno pull. But you also have to exercise some caution on the desensitizing. The timing corrections are there for a good reason. You cannot "pull all the teeth" out of the IAT spark correction tables or you'll end up with timing still being pulled, only now for different reasons. Finally, fuel is going to play a role in this too.

ZZ06

Even though no one has posted in this thread a couple months, its still a great read and there is knowledge to be had here from you guys. Thanks