Suburban 2500 6.0 Issues

NCJeepin

Well-Known Member
Joined
Mar 23, 2005
Location
Conway, SC
Hey all, I just purchased a 2500 burb with the 6.0 gas motor. 208K miles.

I'm having the following problems.

1. At random points of startup I have a tapping coming from the engine, once its driven a little bit it goes away, runs fine during this time. Not an issue but may help with diagnosis with the other issues.

2. At random times, the engine will run very rough and at times the SES light will start flashing. Pulls a P0300 code, multiple misfires.

I can then pull over turn it off, restart it and it runs fine or just a little rough but no light until I drive it for a while longer.

This is a very intermittent issue and started the day after I purchased it. Previous owner stated he recently did a tuneup, all the wires, etc look good and after a visual inspection I can't find anything out of sort.

This is my first later model GM product, any help from you GM guys would be great help. This is my primary driver, and I need to get this issue ironed out ASAP.
 
the tapping noise is most likely piston slap, noisy when cold mostly, pretty much gone when hot. know issue, it's noise, some were worse than others.

the misfire, plugs and wires, start there. my work van started running like this 124k, still had original plugs and wires, pulle dthe plugs, 3 were missing the thin electrode in the center, just pretty much burned /eroded away. ran much better after tune up. You don't give a model year, If I remember right after '04 there was no serviceable fuel filter, it gets replaced with the fuel pump module in the tank. earlier than that still had a frame mounted fuel filter.
 
I would think a neighborhood parts store might let you test out the spark plug theory, good luck with it.
 
It's probably the coils. I chased a misfire for a while myself. I swapped the coils around and it followed them, therefore, I knew it was that particular coil. See which cyl(s) it says are misfiring and give it a try. Just be sure to replace them with AC Delco coils and not whatever Advance or Auto Zone has. Mine would pop a code sometimes, especially if I was on a trip, but you wouldn't even feel it misfire.

It's about 50 bucks or so for the AC Delco coil. Mine wanted two of them. Number 2 and then number 3. Not a minute's trouble since replacing them.


The piston slap is nothing to worry about. I know it sounds horrific, but it won't hurt a thing. I wouldn't exactly call that thing a "basket case" ;)
 
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Croatan_Kid said:
I wouldn't exactly call that thing a "basket case" ;)
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If these were the only issues, I would totally agree, my main concern is to get the thing running properly and then I can handle the rest of the issues. Most others are various electrical gremlins, non-engine related.

The error report I get is multiple misfires, there isn't a specific cylinder noted on my scanner. Do I need to find a better scanner to get the specific cylinders?

As for the relearn procedure, after reading that thread, it could be a fix. thanks for all the help!
 
The nice thing about a relearn is although it will take a high end scanner it should be cheap and non-invasive. If someone did a shade tree tuneup it could definately be part of the problem.
 
Definitely not a crank relearn. I have put 100's of thousands of miles on gm trucks and have NEVER had to do a crank relearn for plugs and wires. It doesn't even make sense that you would need to. If it were related to a crank relearn the problem would not have surfaced 3-4 months later. I would bet money that it is a coil pack.
 
jimbo92 said:
Definitely not a crank relearn. I have put 100's of thousands of miles on gm trucks and have NEVER had to do a crank relearn for plugs and wires. It doesn't even make sense that you would need to. If it were related to a crank relearn the problem would not have surfaced 3-4 months later. I would bet money that it is a coil pack.
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I didn't know this was 3-4 months later. Thought it was right after he bought it and tuneup was right before. I don't know the 6.0 at all just found that thread where several people cited needing one and it being intermittent. I imagine like any electrical gremlin most don't but some do.
 
Want to make it clear, Jim let me inspect and drive the Burb uninhibited before I bought it, it didn't show any of these issues, and I do not see any funny business going on here, as far as I'm concerned he is a straight up guy and worked me a decent deal on the vehicle. Hopefully I can get to the bottom of my issues and start enjoying it.


I just am dumb to chevys and looking to get to the bottom of my issues as cheaply as possible.
 
Jim,

Just noticed where you said you bet its a coil pack. I'm showing a multiple cylinder misfire, my scanner isn't telling me which one. If I get a hold of a better scanner would it, or is this just something I have to go hunting for?
 
Also a valid point about the fuel pump. Does the sending unit give you catty wampus readings? That's usually a tell-tale sign of one fixin to poo the bed.

If you were closer, I would hook up my laptop and check it out. I've got HP Tuners and their VCM Scanner is simply awesome.
 
Sending unit works fine.. I finally decided to drive it some today... Put about 50 miles on it, normal traffic and some 75mph highway speeds... Ran flawless until I got in my driveway then started to run just a little rough before i shut her down..

This screams electrical to me.

I also checked my fuel pressure regulator, and the vac line is completely dry, so I'm thinking that means its good to go?

I want to say its a coil going crazy on me, but I would hope it would give me specific code for a specific coil instead of the multiple.

Croatan_Kid, I really appreciate the offer, I wish i was too. grew up in Morehead City and miss it at times!

There isn't a chance that software is freeware is it? I have a bluetooth ODB scanner I use with my cell phone, which i'm sure my laptop would hook up to as well.

Thanks for all the feedback!
 
I hate that is happening to you. When I test drove the burb, it ran great. I didnt hear any piston slap when I started it up cold. I researched the common 6.0 issues and was listening for the slap. I took it on a good 30 minute test drive. Stop and go -> interstate -> stop and go -> interstate -> stop and go.
 
Update:

Went through the engine bay and disconnected and reconnected every coil wire, cleared the DTC.

Within the last 4 days I've logged over 500 miles trouble free no codes, but it does still idle a little rough at times.

Not sure if I fixed anything but so far so good.... This has been such an odd issue.

Thanks everyone for their help.... I will say she is one thirsty bitch!
 
Get a decent tune in it and it won't be so bad. :D


Nah, the software has to work with the HP Tuners interface. It's capabilities are endless, but for 700 bucks, I expect it to be!


When you say rough idle...how rough are we talking? Like...stumbling or just enough to ripple your coffee?
 
Issues creeped back up today. Somebody please remind me why I didn't stick with a ford?

I'm to the point I'm just ready to unload it, can't rely on it to do what I planned on doing with it, and with the issues I'm going to loose my ass.... Epic fail!
 
FYI from a 2nd forum similar issues:
It sounds like a cheap last ditch try, just saying

Re: 6 liter misfire!
by vic401 » Oct 28 2012, 2:59pm
you need to get a crank relearn done with someone who has either a gm tech2 scanner or something similar, my truck also 04 2500hd(gmc) was having this problem i tried plugs wires and a few other things and nothing worked, after the re learn i havent had a problem or engine light yet, the guy i had do it was alomst trying to talk me out of it saying it wont work but it really does
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