I posted this in another forum, but was advised to repost here since it is about a 6.0...
I have a 2004 6.0l truck with 47,000 miles on it. Sometimes when it starts, it lopes, then goes into a fast idle, but eventually settles into a normal idle.
But I took it out the other day and it started making a "backfire" noise under the hood upon hard acceleration. Normal acceleration it doesn't do it.
After a while, this behavior stopped and I could hard accelerate and everything is great. But then, it came back doing it again. I did notice it smoothed out temporarily when I put in a fuel additive, but that is still in the tank.
Anyone have a clue what is happening? It isn't backfiring out the exhaust. Seems to be under the hood. Thanks for any ideas!

 

Intake valve hanging open a bit?
idk haven't heard of that one before

 

Sounds like a sticky EGR valve (if you still have it in).

Pull it out and look at its condition, and also look in to the intake plenum to see its condition (wet, full of oil residue, crud buildup etc).

 

Sticky EGR? Have you seen this behavior with EGR valves? Why would they cause a "popping" sound and momentary hesitations? Just asking, since I am new to the 6.0

Thanks.

 

Codes
gauges

the only popping noise common to these would be the pop from intercooler boot blowing off under high boost this isn’t that

 

No codes at all.

 

What are you using as a scan tool?

 

Using a software too with an OBD2 bluetooth plug. The software is called Torque Pro

 

We are familiar with Torque Pro. It is usually pretty good at retrieving most/all codes.

Doesn't sound like an issue w/ a sticky EGR valve, and a sticky EGR valve usually produces a code or two.

For that reason, I am thinking an injector might be acting up mechanically (if it is acting up electrically, it usually will also throw a code).
What oil are you using?
When was it last changed?
What is your ambient temperature in the mornings?

Five suggestions:
1. Get a sensor and gauge for fuel pressure.
2. Take a video of the issue and post on youtube (put a link in this thread).
3. Post a pic of the top of your engine (be sure to include the oil filter in the pic).
4. Verify that all three FICM connectors are plugged in.
5. Continue using a quality fuel additive - just to see if the improvement you saw really MIGHT BE from the additive, or that it was only a coincidence.

 

UPDATE: I drove around a lot today and noticed that the sound only happens in a coule of conditions.
First, it doesn't happen under mild acceleration
Secondly, it ALWAYS happens in the RPM range of 1800-2000 RPM and then only under hard acceleration.
Thirdly, the truck purrs normally and the engine doesn't throw codes.

Finally, on cold startup at about the one minute mark after start, the truck typically will go into a high idle (1200 RPM) very suddenly. It will gradually go down to normal when the engine gets up to operating temp.

Could all these issues be related? If so, how?

Thanks.