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CEL, misfiring, and running rough

NMNTruckin

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I’m at a loss now and need some help. My truck started misfiring like crazy non-stop. She idles rough, runs rough, has significant loss of power, and is burning through fuel. I’ve replaced the plugs, wires, MAF sensor, air filter, and fuel pump. The coils seem to be fine, and there’s no water in the fuel. I don’t know what else it could be. The scanner is still reading a bad MAF sensor. Any suggestions?
 

2004Slickside

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As you can clearly attest to, codes from scanners are not indicative of bad parts. Codes are only there as a starting point in a factory diagnostic chart. To begin, fix the problem that is setting the MAF sensor code. I assume you have a 2002 - 2006 since you posted here. I'll attach the diagnostic chart(s), but you will have to tell me exactly what vehicle you have and which codes are appearing. You will need your own scanner if you want to work on this problem. I can recommend one if you don't have it.
 
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ygmn

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WHat are actual codes?
What year?
 

Drew

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I’m at a loss now and need some help. My truck started misfiring like crazy non-stop. She idles rough, runs rough, has significant loss of power, and is burning through fuel. I’ve replaced the plugs, wires, MAF sensor, air filter, and fuel pump. The coils seem to be fine, and there’s no water in the fuel. I don’t know what else it could be. The scanner is still reading a bad MAF sensor. Any suggestions?
Same happened to me turned out to be my AFM lifters (Active Fuel Management) that collapsed. If you have any misfire codes and hear tapping then you have a collapsed lifter(s).
 

Raekal

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Unless i'm mistaken by their profile picture, they have a 1st gen avalanche which doesn't have the AFM "feature".
 

NMNTruckin

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Sorry for the late reply guys, but I appreciate all the input. Yes, I have a first generation 2004. The codes that it’s pulling our P305, P102, P171, and P174.
 

NMNTruckin

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I actually just did the fuel injectors, and it’s worse. Before it was just pulling in the code P305. Now it’s pulling all the codes I just sent out.
 

ygmn

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Did you go thru trouble shooting procedures for each code?


ANother trick is clear allthe codes and then run again until check engine light comes on and then turn off and read code(s)
Sometimes one issue can force many codes.

Ever check intake manifold gasket for air leaks?
OR any intake leak after MAF?
Maybe vacuum line?


many good sites out there to help... remember your engine was used on about every GM truck and full size SUV so many could have the same issues
 

NMNTruckin

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Just an update guys….

I ended up checking the plugs we installed and it turns out the parts store sold me Platinum ACDelco plugs. I didn’t even pay attention when I bought them, but now learned my lesson.

The truck calls for Iridium plugs so after searching every parts store in my area, I finally found some NGK Iridium plugs and got them. Just swapped all the plugs out, and now she is running great! The CEL is off and she’s not misfiring anymore.

I appreciate all the feedback and suggestions.

Thanks everyone and have a great 4th!
 

2SmokinBarrels

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great news NMNTruckin. Seams like a easy fix. Especially the way it was looking, almost tore the engine apart lol.
Do those NGK Iridium plugs apply to my '04 z71, 5.3 as well?
 

Raekal

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great news NMNTruckin. Seams like a easy fix. Especially the way it was looking, almost tore the engine apart lol.
Do those NGK Iridium plugs apply to my '04 z71, 5.3 as well?
For all I know, you definitely want to be putting at least iridiums in thse motors. I've definitely seen a couple cases where trucks are suddenly running rough after plugs, and it usually winds up being that autozone sold them the platinums instead. Which, seems somewhat odd that it causes a substantial problem if the gaps are the same between them, but i'm not about to go two plug jobs to find out. lol.

If going NGK, specifically go for the slightly more expensive laser iridiums. Apparently they last a decent amount longer than the standard ones they sell. (50-100% longer depending on who you ask)

Strangely, they dont have lasers available for the 8.1l on rock auto, so I think i'm going to wind up trying the ruthenium's out.
 
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NMNTruckin

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great news NMNTruckin. Seams like a easy fix. Especially the way it was looking, almost tore the engine apart lol.
Do those NGK Iridium plugs apply to my '04 z71, 5.3 as well?
I believe they do. Not sure why the parts store didn’t know what was OE requirement for my truck.
 

2004Slickside

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Copper Spark Plugs vs. Iridium and Platinum: Understand for Top Performance​

Many people come to the point where they are forced to change the spark plugs on their vehicle and face a difficult decision; copper spark plugs or those of another type? You can find spark plugs in a variety of different metal combinations, including aluminum spark plugs, iridium plugs, platinum and more. Copper core spark plugs are still the most commonly seen, however, and many people agree that they are the best. However, the advertising that accompanies the different types of spark plugs is potentially misleading, so it's important to recognize the real difference between the spark plugs in question. In order to do that, it's necessary to first learn about what the metal in the spark plug is used for.

Purpose of the Metal

The metal in a spark plug serves a single basic purpose: to channel the electric energy from the plug wire through the spark plug so that it can be forced to the engine block in the form of a spark. Therefore, any metal that conducts electricity at all could potentially be used for a spark plug. The metal should also not get too hot; one of the main problems with some metals is that they overheat quickly, causing the electric charge itself to be compromised and the spark plug to not operate as smoothly.

Copper Spark Plugs

Copper spark plugs are generally considered to have the best performance of any spark plug type. This is potentially different from what advertising companies suggest, but the other metals are, unfortunately, not as conductive in general as copper is. Platinum and iridium plugs are more likely to overheat, which causes damage to the plug components and can compromise the delivery of the spark to the engine block.

Platinum and Iridium Plugs
Platinum and Iridium plugs perform at a lower level than copper spark plugs, because they are less conductive and they tend to overheat. However, the overall longevity of these two types of metal is better than copper plugs. In reality, copper has the best performance of all three and the worst longevity. Platinum has good longevity and the worst performance. Iridium has good longevity and a performance that is decent, which is why iridium plugs tend to be more expensive than any other type. Still, the difference between these plugs in terms of overall quality is minimal, as there is a trade off for each.
Most copper plugs need to be changed every 20,000 miles or so. Platinum and iridium plugs can often go for twice that before they require changing, but the overall performance will not be as good and you may have to deal with overheating of the plugs. This is potentially not worth the added cost of both platinum and iridium spark plugs, although the decision will depend upon your preference.
 

Raekal

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Most of that is true, though modern plugs last well beyond 40k miles making it frankly a no-brainer unless you specifically want copper for a classic car. I don't know anyone that has anything other than a 4-cylinder that would willingly want to change their plugs every year (or more) outside of racing applications.

Waste spark systems, such as those in Chrysler's double plug setup on their v8's, also require at least double platinum in order to extend life, as the arcs travel in both directions and "strike" both electrodes instead of just the one. Double plats and most iridiums have an additional platinum puck on the ground electrode, increasing their life drastically in these applications. Though to an extent I imagine it also reduces the general wear in more standard applications.

Upon further review, this is the larger difference between laser iridiums and iridium IX plugs from NGK. Lasers have the additional puck, which increases life over the IX models and explains why people can see drastically better lifespans out of them depending on application.

Iridium withstands heat far better than platinum and if it produces a better spark, makes sense why there isa difference in how the engine runs. Every little bit screws with the timing.


Realistically, ruthenium is usually found alongside platinum and likely is cheaper than iridium to produce so someday we may see those take over if they pan out to offer even better life. Just need the free market to adapt and bring costs down. People claim they burn fuel a little cleaner thanks to the plug design. Time will tell. I still may try them for kicks and giggles. Not expecting miracles, but I do like not having to change them. If they work and last like they should, ill be happy.
 
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Drew

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Just an update guys….

I ended up checking the plugs we installed and it turns out the parts store sold me Platinum ACDelco plugs. I didn’t even pay attention when I bought them, but now learned my lesson.

The truck calls for Iridium plugs so after searching every parts store in my area, I finally found some NGK Iridium plugs and got them. Just swapped all the plugs out, and now she is running great! The CEL is off and she’s not misfiring anymore.

I appreciate all the feedback and suggestions.

Thanks everyone and have a great 4th!
Good to hear. Crazy all of that from incorrect spark plugs.
 

NMNTruckin

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She was running good for a little while, and now she’s misfiring again. Hopefully I can figure this one out quicker. Also, any ideas as to why the four-wheel-drive would put itself in neutral? I noticed when I started her up the four-wheel-drive was set to neutral.
 

2SmokinBarrels

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NMNT, I have a couple friends having Chevy engine trouble. One believes its his timing chain. The other discovered his ECU was very badly corroded.
The 4x4, could be the actuator / encoder motor on the front diff , or the wires.
Could take a look at ground straps too. maybe broke or corroded.
Just tossing ideas:B:
 

Raekal

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She was running good for a little while, and now she’s misfiring again. Hopefully I can figure this one out quicker. Also, any ideas as to why the four-wheel-drive would put itself in neutral? I noticed when I started her up the four-wheel-drive was set to neutral.
Are you dealing with the same codes as before or different ones?
 

Dron

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I’m at a loss now and need some help. My truck started misfiring like crazy non-stop. She idles rough, runs rough, has significant loss of power, and is burning through fuel. I’ve replaced the plugs, wires, MAF sensor, air filter, and fuel pump. The coils seem to be fine, and there’s no water in the fuel. I don’t know what else it could be. The scanner is still reading a bad MAF sensor. Any suggestions?
I had misfire issue after replacing an engine. I had p0300 and p0101 MAF (I think last one is correct cod). You have misfire p0305 it is 5th cylinder. Pull sparkplug and see if it wet or dry.
I'm a not auto mechanic.
I'll check:
1) fuel pressure on the rails (58 psi)
2) injectors plugs. I replaced all driver side injector pigtails on my AV. Old plugs warren stay pugged ($20 for a set on Amazon).
3) Vacuum leaks. Intake gasket goes bad around 150K. Intake gasket was cracked on my Escalade 170K, codes P0171 and P0174.
4) Check injectors flow. I lost 2 engines due to stoked injector. Hydro locked engines.

I started same way your are going. Replaced sparkplugs, wires, fuel filter, Clean MAF, swap MAF from a working truck.
In my case. I relearned crank shaft position sensor and p0300 goes away.
This was my case, because a new engine and PCM need to adjusted to new sensor.

Do you have a rodent? I had ants in one of my fuse boxes. Chipmunks loves air filter, cabin heater duct and space under the fuse box. Check the wires.
 
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NMNTruckin

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NMNT, I have a couple friends having Chevy engine trouble. One believes its his timing chain. The other discovered his ECU was very badly corroded.
The 4x4, could be the actuator / encoder motor on the front diff , or the wires.
Could take a look at ground straps too. maybe broke or corroded.
Just tossing ideas:B:
It was suggested that the truck might need a new ECU.
 

2SmokinBarrels

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Yes I think the ECU fixed his problem. '03 silverado 6.0.
These trucks have a mind of their own. Mine surprises me Everyday lol
My engine light went out today and the horn quit lol but thats another thread
 

Raekal

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Yes I think the ECU fixed his problem. '03 silverado 6.0.
These trucks have a mind of their own. Mine surprises me Everyday lol
My engine light went out today and the horn quit lol but thats another thread
It's all fun and games until the horn switch starts controlling other things. I love seeing threads on r/justrolledintotheshop where they smack the horn on a BMW and the windshield wipers start going and turning the headlights on honks the horn.
Same codes.

Another thing to test if you have not already is to do a leak down check of the cylinders. If your cylinder rings are going out you can run into an issue where the rest of the system is working fine, but you're losing energy from the power stroke back into the crank case. As a result of the reduced power, the computer calls a misfire because there's a negative change in rpm, harmonics, and emissions. it may be igniting properly and getting the correct fuel, but it's like drilling a hole in your piston - the explosion just cant give the crankshaft the "oomph" that it should. Then when the next good cylinder fires it "feels" rougher because it's kicking the rpm's back up. Because the rings move and flex, you can get inconsistent compression which doesnt help when trying to diagnose.



Sometimes when pulling a plug, it can be fowled on oil if the wipe ring is allowing oil to get into the bore which can reduce the performance of ignition on top of it and exasperating the issue.

just one more thing to try
 
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