Random Backfire under moderate to heavy acceleration

Yup stock RC12ECC sir. Couple bucks a plug. Should fix your woes. If not I also agree with Crank and Cam Sensors. Cam sensor requires special install so don't just "stick it in":D when replacing. It sits in there at a specific depth ;-)
 
Well, too late on the plugs. I replaced them with the same type. They were actually in there for about 26,000 miles after I thought about it some more and I never had issues with them until 3 days ago. Well maybe not...

Anyway, it was not the problem. It seems to do it as it gets from cold to hot in operating temperature. It did it after I let it run it run for about 5 minutes idling then drove it. Fell on its face under moderate acceleration in 2nd gear.

Took it to the dealer and could not get it to do it the whole way over after it did it initially. WOT onto interstate from ramp. WOT at highway speeds. Ran like a rapped ape. :confused:

By the time I got it there no one was able to look at it anyway. The service writer was a nice guy but he had no idea what I was talking about.

SM says possible causes for miss on accel are:

Plugs
Wires
Dirty fuel
Burned, warped, or pitted valves
Coils

Aside what you guys mentioned I guess we will have to see what the dealer can find. Probably nothing because it won't do it for them, I'm sure.

My gut tells me coil but then again my gut has been wrong before. :D
 
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Might be the cam sensor like some of the guys were saying. Best to start with the easy stuff and work your way up. Now that plugs are ruled out, it wouldnt hurt to go ahead and change your wires, and if your gonna change your wires, you have the option to do the coils also.
 
Not sure if you read my post but I had the exact same problem, and it was the injectors, one was not firing, have you checked ? make sure there are none loose


SlvrSnake said:
Well, too late on the plugs. I replaced them with the same type. They were actually in there for about 26,000 miles after I thought about it some more and I never had issues with them until 3 days ago. Well maybe not...

Anyway, it was not the problem. It seems to do it as it gets from cold to hot in operating temperature. It did it after I let it run it run for about 5 minutes idling then drove it. Fell on its face under moderate acceleration in 2nd gear.

Took it to the dealer and could not get it to do it the whole way over after it did it initially. WOT onto interstate from ramp. WOT at highway speeds. Ran like a rapped ape. :confused:

By the time I got it there no one was able to look at it anyway. The service writer was a nice guy but he had no idea what I was talking about.

SM says possible causes for miss on accel are:

Plugs
Wires
Dirty fuel
Burned, warped, or pitted valves
Coils

Aside what you guys mentioned I guess we will have to see what the dealer can find. Probably nothing because it won't do it for them, I'm sure.

My gut tells me coil but then again my gut has been wrong before. :D
Click to expand...
 
Got it back from dealer today and nothing was done and they could not recreate the issue. However, I could.

It happens as it warms up, basically between cold and hot cycle. Pretty much stops right at 4,000 RPM and acts like it is hitting a rev limiter and misses like a mofo. However, it has not yet thrown any codes which I find odd.

Venomous, when you had your injector issue was it anything like this?

The mechanic watched the video on my phone and he was at a loss. His best guess at the time was an O2 sensor. However, I thought that when O2 sensors would go that the PCM would go rich not lean?

Anyway, that is just an update with a little more info.

As for the other stuff it needs a new trans and two new front calipers. Seriously debating parting ways with the beast. Getting tired of the issues with this thing.
 
Alright here is a video of it doing what I have been describing. It's not the best but it was raining and it was dicey holding my phone and trying to recreate this issue at the same time.

I did this right at the dealer and then went back in and made an ass out of myself because I was beyond pissed because I explained to them exactly the conditions I had observed to recreate the problem and apparently they could not. Hence the reason I took a damn video of it.

Anyway, see what you think.

This is stock tune, I have 172 T-stat and you can see the temp has not reached full operating temp yet at 200. This is when it does it. Has not yet done it cold or hot and has not thrown a code.

Turn up your volume to really hear it. It seems to fall flat right at 4K and just stay there.

VID_20130524_135511_536 | Flickr - Photo Sharing!
 
You can data log to rule out the o2 sensors by looking at the output and making sure they're cycling. I don't think it's an o2 issue because they are not used in Open Loop operation.

What trans issue is it?

I would take a look at the plugs and not drive it hard with the issue.
 
SlvrSnake said:
This is stock tune, I have 172 T-stat and you can see the temp has not reached full operating temp yet at 200. This is when it does it. Has not yet done it cold or hot and has not thrown a code.
Click to expand...

So it does not back fire once the truck is up to operating temp?
 
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