Before you rip into it, I'd try a few simple things:

Do your aforementioned simple checks. Add some injector cleaner to the tank, and fill up with a fresh pot of fuel. Get the car warm, and then take it out on a really enthusiastic Italian tune-up. Hard driving is under rated as a maintenance strategy. (Seriously)

 

Well, I tried 2 tanks of 93 octane gas with a full bottle of Chevron Techron in each tankfull. It didn't seem to make any difference.

I'll give the "Italian tune-up" a try.

Thanks for the suggestions!

Yogi

 

Yogi, are you getting any P-Codes?
Are the misfire moving from cylinder to cylinder?
They say misfires are very hard to find in troubleshooting but we can try and help you Yogi...

 

I'm not getting any CEL. Does ANY misfire set a code, or just severe misfires?

Yogi

 

Here's an interesting video. It's specifically about Ford Ecoboost engines, but a lot of it applies the Redline and GXP.

https://www.youtube.com/watch?v=-ynGWxzJHjA

 

Thanks, Rusty.

Yogi

 

For anyone who is interested in the walnut shell cleaning method, here is a good thread about it with lots of pics: http://www.cobaltss.net/forums/how-guide-43/how-valve-gunk-coking-removal-304188/

Yogi

 

I do understand the difference between direct injection and multiport injection, however, I still believe that the additional heat generated with enthusiastic driving is worth something when it comes to cleaning the engine out.

 

Doing some more research, I just found this GM service bulletin (PIP5029) Dated May 29,2012 (Attached).

They recommend using Kent Moore J 35800 A Fuel Injection Cleaner Special Tool | eBay to pump GM "Upper Engine and Fuel Injector Cleaner" into the intake manifold. Here is a similar tool at Amazon: Amazon.com: OTC 7448 Fuel Injection Cleaner: Automotive

Also see the 9/15/2014 post by Drillbabydrill for a rather unorthodox method: Valve cleaning for Turbo DI engine's | Fuels and Fuel Additives: Gasoline and Diesel | Bob Is The Oil Guy

He filled a 16 oz. bottle with 50/50 water and hydrogen peroxide, then sucked it into the intake. No pics, but he claims that boroscope proved that it worked.

Yogi

 

Vic is right about the code area. However, P300 is it's own code for Random Misfire and can generate without a P30X code for the affected cylinder. Not every misfire will throw a P300 series code and usually it takes multiple misfire events to have a code throw the Check Engine Light (CEL).

The ECM does differentiate between a minor random misfire event (say you have one stumble in one cylinder), a not so minor random misfire event (stores a pending code and, after a number of these events, throws a CEL), and a major misfire event (engine is constantly misfiring causing the ECM to flash the CEL while the event is occurring).

 

OK, Thanks Robo.

Yogi

 

Hi Yogi

First change your plugs. Next go to the parts store and buy a can of SeaFoam. You can use this in the fuel system and oil as well. Then go drive it spirited and that should clear it up.:thumbs: or you could do what We use to do with the old Chev 350s. Poor a little water right in the intake while it's running. Kind of hard to do with a turbo unless you want to run it thru there too but not sure what it would do. If it's just a small amount of water and you poor slow it shouldn't hurt it a bit I would think. The cold water on hot valves breaks the carbon right off and out the exhaust. I'm sure if you were driving in a hard rain a little water gets in anyway. Water/alcohol injection does the same thing:thumbs:
Let us know what happens.

 

Poor a little water right in the intake while it's running. Kind of hard to do with a turbo unless you want to run it thru there too but not sure what it would do.

Or you disconnect the vac line running from the intake manifold to the brake booster on the brake booster side and you let that suck up the water...


...That's how we use to do the SeaFoam treatment on the Supercharged Grand Prix to avoid the stuff getting sucked through the blower.

 

OK. Thanks Rick and Robo.

Yogi

 

I forgot to mention that I took it to O'Riely's last night. It was about a 1/3 mile trip from my house and it was missing noticeably most of the way. They said that there were no stored codes (No CEL either).

I guess that I will need HP Tuners or something to get the codes?

Yogi

 

Or get a ODBII dongle off eBay for $10 (or $100 if you want the high speed one that lets you data log reliably too) and the Torque app (if you have an Android phone/tablet...there is a different one for Apple products...never can remember the name) and pay the $5 for the Pro version.

That will let you scan for codes too for under $20. I have a cheap dongle in my car at all times so I can pull codes whenever they come up.

Though if they said it had no codes, Torque or HP Tuners wouldn't show anything either.

 

I don't understand. How can it be obviously misfiring and not at least store a code? I thought that the misfiring detection was pretty sensitive, or not?

Thanks for the Data Logger info, Robo!

Yogi

 

Good question. Maybe it has something to do with it only doing it when cold. Maybe it won't log misfire events until the engine coolant temp is up to a certain operating level. I don't know how the logic for that is written.

 

That is one of the reasons why it's very hard to trouble shoot misfires! :cheers:

 

Yes the one I have that you say its huge also works off of "Torque" does what yours does a lot more!

 

Reading the description the only thing it can do mine can't is attach aftermarket sensor like my Wideband. Everything else it can do, mine can do. If I were to get a better dongle, the speed at which data is captures would let Torque log data too and the improved version is only slightly larger than this version. No 3' cord necessary.

I have a long cord like that on HPTuners and that gets in the way all the time when I'm scanning with it...drives me nuts. But HPTuners does a lot more than either of these.

 

Their just has to be a reason for the 3' cord on the PLX interface device....

 

This topic has been discussed at length on other forums. There is definitely an endemic problem with all current design DI engines where the valves build up carbon because they are not washed by incoming fuel.

The intake sees the PCV output which carries hydrocarbon in the flow which plates out on the valves.

Any repair that results in the carbon coming off the valves and going into the intake will cause damage to the motor. Chemicals that are strong enough to actually break down the deposits can also damage the turbo. Either chemically by breaking down the lubrication or mechanically as chunks of material are blasted into the turbine.

To the best of my knowledge based on the reading I have done, and others will correct me I am sure, is media blasting the valves while they are closed and evacuating the resultant solid matter.

Some manufacturers including Ford with their ecoboost engines will void your warrantee if they find that you applied any "fix" other than the one they recommend. The chances of damaging the bearings and / or the turbo are very real.

Hopefully GMtech will weigh in on what the recommended maintenance is and clarify it for all of us.

 

This topic has been discussed at length on other forums. There is definitely an endemic problem with all current design DI engines where the valves build up carbon because they are not washed by incoming fuel.

Do you by chance have links? I'm not trying to be lazy... Sometimes it's easier to recall the thread titles if you've read something in the past. :thumbs:

Either chemically by breaking down the lubrication or mechanically as chunks of material are blasted into the turbine.

How do pieces of material go from the intake valves to the turbine?

How bad are these chunks (of basically ash?) for the cylinders?

Assuming they could cause premature contamination but shouldn't the materials should be the same kinds of crud that's already getting into the cylinders anyway?

Or, when you say "material" are you talking about the abrasive cleaning stuff used to clean out the carbon buildup?

I can't see using any kind of basting as a great option without removing the valves to prevent all that mess and possible contamination. Seems like a lot of work to go that route, but way less than teardown to repair any cylinder damage :banghead:

Hopefully GMtech will weigh in on what the recommended maintenance is and clarify it for all of us.

I remember he said the 5th injector was an good cleaning method. :thumbs:

Seriously though, the "official" GM answer would be good to hear. :agree:

 

Thanks, Robo!

Yogi

 

In case someone reads through all this, I'd suggest:

1). Walnut blasting: Harbor Freight blaster and fine walnuts, get walnut blasting vacuum adapter from Amazon (generic trim to size). Obviously rotate so valves are closed as you do each cylinder.
2). Once the valves are clean, start a cleaning regiment. A few days before every oil change, use some CRC GDI Intake clear and use according to directions to keep intake clean. Do NOT use if intakes are already severely carboned as chunks could come off. Some advice against using any kind of cleaner altogether like this. I think it's ok if you've thoroughly cleaned the valves but I'm not expert.
3). Recheck intakes every 20k with inspection camera (can probably get in there taking off the intake manifold elbow hose from charge pipe, then sticking small inspection camera up there...not sure if that would work. Could take off intake but a bit of a pain.