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Old 01-17-2018, 07:41 PM   #1
Bladeboy1998
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2003 2500hd 6.0 odd vacuum leak issue

Alright guys, I've got a weird one for you. I have a miss fire on cylinder 1, 3, 6, and 8, 8 being the worst. Fuel trims on bank 2 are wayyy rich, almost acts like a vacuum leak, has the high idle, misfire, and fuel trims way off. Propane tested around the intake, no leaks that I can find. So I move on to the smoke machine, still no external leaks. (I'm putting the smoke machine nozzle into the fuel pressure reg vacuum line.) I pulled the pcv hose off, and pluged the intake side. It came out of the valve cover with pressure. Pulled the oil cap, same there.

I have a vacuum leak internally from what I can see. So I pulled the valve cover thinking it may be valve stem seals cause the intake valve could be closed and leaking up through into the valve cover. Well turns out its coming from the pushrod galleys. My next thought was rings, did a compression test on bank 2 side, all were at 130 psi +- 3 pounds. Compression is perfect.

Got a new plug for cyl 8 cause I broke it anyways, and moved the coil from cyl 2 to cyl 8, and the misfire stayed on 8.

I feel like I'm chasing 2 different problems, but I'm lost. It's killing my fuel economy too
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Old 01-20-2018, 07:34 PM   #2
izzy_Britton
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Re: 2003 2500hd 6.0 odd vacuum leak issue

I am by no means an expert. I am just thinking out loud and guessing right along with you.


NO CODES?


it kinda sounds like you might have a a coil pack wire harness short somewhere? with both sides of the engine having misfires it doesn't sound like the coils them selves are having issues or that only a single side coil harness is having issues. can you disconnect the coil pack harness mail connector and clean the connectors with some circuit board cleaner and plug it all back in to see if that helps?

another thought sounds like maybe the injectors got some gunk in them and is clogging or partially clogging the injectors?
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Old 01-21-2018, 02:28 PM   #3
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Re: 2003 2500hd 6.0 odd vacuum leak issue

There is a po300 random multi cylinder misfire code that doesn't throw a light, but it's in history codes. I'll try cleaning connections and maybe move injectors around. I'm still concerned about the smoke test coming out of the push rod galleys. I don't get how that woukd happen except rings or valve seals, and both seem fine.
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Old 01-21-2018, 07:55 PM   #4
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Re: 2003 2500hd 6.0 odd vacuum leak issue

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Originally Posted by Bladeboy1998 View Post
There is a po300 random multi cylinder misfire code that doesn't throw a light, but it's in history codes. I'll try cleaning connections and maybe move injectors around. I'm still concerned about the smoke test coming out of the push rod galleys. I don't get how that woukd happen except rings or valve seals, and both seem fine.
I would take a spark plug and put it in the number 8 plug wire leave the plug in the head use a extra spark plug and start it to see ifs its sparking if it does spark make sure it fires rapidly if not or no spark its the coil. or a bad wire somewhere to the coil or maybe the plug wire may be bad
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Old 01-21-2018, 08:35 PM   #5
95 S_Trucker
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Re: 2003 2500hd 6.0 odd vacuum leak issue

Find or borrow a good scan tool, and under data display, look in misfire history. I can almost guarantee you'll find a cylinder that has a lot more misfires than the others.
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Old 01-21-2018, 08:38 PM   #6
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Re: 2003 2500hd 6.0 odd vacuum leak issue

It is common for the smoke to go past the rings. It's best to do a smoke test on a cold engine before the intake gaskets swell. Since the engine is cold, it will have a little more scooting past the rings.
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Old 01-21-2018, 08:38 PM   #7
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Re: 2003 2500hd 6.0 odd vacuum leak issue

am i the only one that is getting the plain jane forums from yesteryear or is this the new norm?

anyways, i have a question about your smoke test. you said that you plugged the smoke into the pcv valve, on the engine or the intake? if you plugged it into the engine side, smoke makes sense coming from the push rod galley as the entire engine is open with exception of the cylinders. smoke in the valve cover pcv will eventually wind its way down the pushrod holes, to the cam and the lower engine and then it will work its way out wehere ever there is a hole, obviously you know this or you wouldnt have a smoke machine.

second thought being if you are smoke pressurizing the intake manifold and getting smoke out the valve covers or the pushrod tubes then i would have to GUESS that maybe the valve stem seals are bad, or maybe rings, but if it was rings i would also imagine that the plugs would foul more often than not because of burning oil.

i have never used propane to test for intake leaks, i have always used brake cleaner or engine cleaner or starting fluid to spray around the suspected leak area to listen for the rpm change. is using propane as efficient (i guess that is the word i could use) at determining leaks as a flammable liquid aerosol like brake cleaner?

just thinking out loud, i know nothing.
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Old 01-21-2018, 10:00 PM   #8
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Re: 2003 2500hd 6.0 odd vacuum leak issue

Check the fuel pressure while driving.it should be about 65 psi. Your smoke test results are normal.
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Old 01-27-2018, 05:53 PM   #9
Bladeboy1998
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Re: 2003 2500hd 6.0 odd vacuum leak issue

Quote:
Originally Posted by izzy_Britton View Post
am i the only one that is getting the plain jane forums from yesteryear or is this the new norm?

anyways, i have a question about your smoke test. you said that you plugged the smoke into the pcv valve, on the engine or the intake? if you plugged it into the engine side, smoke makes sense coming from the push rod galley as the entire engine is open with exception of the cylinders. smoke in the valve cover pcv will eventually wind its way down the pushrod holes, to the cam and the lower engine and then it will work its way out wehere ever there is a hole, obviously you know this or you wouldnt have a smoke machine.

second thought being if you are smoke pressurizing the intake manifold and getting smoke out the valve covers or the pushrod tubes then i would have to GUESS that maybe the valve stem seals are bad, or maybe rings, but if it was rings i would also imagine that the plugs would foul more often than not because of burning oil.

i have never used propane to test for intake leaks, i have always used brake cleaner or engine cleaner or starting fluid to spray around the suspected leak area to listen for the rpm change. is using propane as efficient (i guess that is the word i could use) at determining leaks as a flammable liquid aerosol like brake cleaner?

just thinking out loud, i know nothing.
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Sorry I was a little unclear, I put the smoke machine nozzle into the intake manifold, where the pcv goes into the intake. I only ran about 5 pounds of pressure out of the smoke machine. It came out of the pcv valve and the oil cap. I pulled the passenger valve cover and the smoke was coming out of the push rod galleys at a pretty good velocity, more than I would think ring gap would allow.

The plugs aren't fouling really, they do have about 60k on them, and they are acdelco double platinum plugs.

At work we use propane cause it makes more of a noticeable difference in the oxygen sensors on the scan tool. Instead of just listening for rpm change, you see data change.
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Old 01-27-2018, 05:55 PM   #10
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Re: 2003 2500hd 6.0 odd vacuum leak issue

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Check the fuel pressure while driving.it should be about 65 psi. Your smoke test results are normal.
Its at 62 pounds key on engine running, did the fuel pump in September, brand new delphi pump. Replaced filter at the same time.
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Old 01-27-2018, 05:58 PM   #11
Bladeboy1998
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Re: 2003 2500hd 6.0 odd vacuum leak issue

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Originally Posted by 95 S_Trucker View Post
Find or borrow a good scan tool, and under data display, look in misfire history. I can almost guarantee you'll find a cylinder that has a lot more misfires than the others.
I'm using a matco maximus gen 1 scan tool, it's made by launch. Not a low end scan tool, but it's not a snap on one. I did use my buddies snap on one, before this all happened and even then we never got any live misfire data.
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Old 01-27-2018, 06:07 PM   #12
Bladeboy1998
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Re: 2003 2500hd 6.0 odd vacuum leak issue

Long term fuel trim on bank 2 shows full lean (so it's enriching fuel mixture). I thonk uou us are right, the smoke test results are normal, thats not an issue. Now that I singled that out, I need to figure out why it's full lean on bank 2, I've already done intake gaskets, tested them multiple times and they don't leak, injector o rings don't leak, I can't find any vacuum leaks. This seems like a simple issue.

I will also add, there is a noise under the intake manifold, it's not a knock, it sounds like it could be lifters though. Could my issue be the dreaded lifter issue? I dont know if they cause a misfire or not.
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