6.2 missing, traction control, stability lights

[FBYamaha]

I've done a bunch of searches and hate to ask in case I'm missing something. 2007 Denali, 6.2, 170,000 miles. Just bought it (back from the ex-wife) It was running great, ran some seafoam through it since I'm pretty sure she did nothing to it since the divorce. Changed the oil. Probably put 1000 miles on it. Fired right up the other day, pulled out of the driveway and is started missing.....badly. Engine light, traction control light, stability control light. I let is sit for a couple days and just fired it up. Starts right up, maybe with a little miss then it goes downhill from there and all symptoms return. When it first happened I changed the plugs and wires. Plugs all looked good. We did have a similar problem three years ago and they replaced a broken valve spring. I can't imagine it would be that again. Any other ideas before I limp it to the repair facility?

 

[wjburken]

What codes are you getting when you scan it with an OBDII?

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here, who will chime in with their suggestions.

 

[FBYamaha]

Thanks fellas. It's the P0300. which as I understand from the searches is a pretty common and broad code. I just hate to start throwing parts at it. At the same time, I also hate to pay $500 for a easy fix. The typical dilemma.

 

[wjburken]

Thanks fellas. It's the P0300. which as I understand from the searches is a pretty common and broad code. I just hate to start throwing parts at it. At the same time, I also hate to pay $500 for a easy fix. The typical dilemma.

Well, the good news is you don’t have AFM in your vehicle so that’s not a possible cause.

P0300 is the only code you are getting, huh.

What exactly do you mean you ran Seafoam through it? Did you put it in the fuel tank? Spray it into the intake? Or put it in the oil? How much did you out in?

Is it making any knocking noises or chirping noises?

 

[FBYamaha]

I could also add I have just bought the Innova 3140 reader so I have the ability to check live if there is something to look for.

 

[FBYamaha]

I first put a can in the tank of seafoam, then after that tank I shot the seafoam spray into the intake, right at the throttle body as directed. It doesn't knock any more or less than the usual minor knock until it gets warmed up. While I had the reader hooked up i ran it for maybe 5 minutes with the rpm's increased just a little. It seemed to get a little better for a few and then just dropped another cylinder or two and got really rough for a minute, picked up again and then off again.

 

[Doubeleive]

Could be several things plugs, wires, coil packs, injector/s, coil pack harness, injector harness, intake leak, maf sensor, low fuel pressure, plugged cat's, bad 02 sensors, bad ground.
or any combination of the above.
how long ago did you do the plugs & wires? and did you oem or something else?
it's probably going to take some troubleshooting
1st thing I would do is check your battery cables and grounds, take a close look at the grounds, take them off wire brush both the cable and the area that it attaches to.
2nd rent or buy a cheapy fuel pressure tester and check your fuel pressure you should get 60-65 pre-start (key turned to run) and around 45-50 with engine running
both of those are easy to do and wont cost you much of anything but a little time.
then take a good look at the injector wire and coil harness wires look for any frayed or broken wires, this also wont cost you anything
then at least you can rule that stuff out and proceed to digging a little deeper.

 

[FBYamaha]

The plugs and wires were the first thing I did when this began, so friday. I did the bosch plugs and regular OEM wire set, nothing out of the ordinary. I've got a fuel pressure tester, so I'll do that no problem. Are these really that sensitive to voltage?! I can't imagine that would cause this, but hey...I'll give it a shot at this point.

 

[Doubeleive]

The plugs and wires were the first thing I did when this began, so friday. I did the bosch plugs and regular OEM wire set, nothing out of the ordinary. I've got a fuel pressure tester, so I'll do that no problem. Are these really that sensitive to voltage?! I can't imagine that would cause this, but hey...I'll give it a shot at this point.

these trucks will do all kinds of weird stuff if the voltage is goofy, so much so that it's one of the first things you want to check when the thing starts not running right or doing goofy stuff, just something to check and rule out. a random misfire could be a bad ground on the coil or injector harness it's not really common but it has been known to happen you could test that by wiggling the wires around while it is idling and see if the problem goes away or comes back. just part of the troubleshooting process especially when it just gives you a generic code.