Misfire or backfire?
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5th Wheeling
Joined: Nov 2025
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Misfire or backfire?
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!
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!
Logistics Pro
Joined: May 2004
Posts: 3,607
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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).
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).
Last edited by joe blow; Nov 26, 2025 at 08:34 AM.
Hotshot
Joined: Apr 2010
Posts: 19,056
Likes: 235
From: Saratoga Springs,UT
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
gauges
the only popping noise common to these would be the pop from intercooler boot blowing off under high boost this isn’t that
Last edited by BLADE35; Nov 26, 2025 at 08:17 PM.
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5th Wheeling
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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.
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.
Last edited by bismic; Nov 28, 2025 at 12:53 PM.
Thread Starter
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5th Wheeling
Joined: Nov 2025
Posts: 32
Likes: 7
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.
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.
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.
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