SOLVED: Another misfire chasing threads (2008 express van)

[exp500]

Not exactly what I wanted to see, But usable. Your vacuum is low. How much of that is EGR I don't know (decel). At your most efficient cruise speed, engine vac should be 17-19. That shows rings or valve leakage (again EGR involved in number) . So what it points to from two short partial tests is small Vacuum leak somewhere or leaky EGR or sticky lifter/carboned valve (that 2 inch vac drop miss at idle). Recommend an oil change and a can of berrymans in gas for(#7) with read thru on vac gage diag especially a 60's chart that shows more tests.
Vac diagnosis is valuable in steady state runs usually, as hiccups show. Between your scanner recording live data and a glance at the vac guage occasionally or when you feel a change should generate a solution. Keep posting results and Good luck.

 

[Tonyv__]

Not exactly what I wanted to see, But usable. Your vacuum is low. How much of that is EGR I don't know (decel). At your most efficient cruise speed, engine vac should be 17-19. That shows rings or valve leakage (again EGR involved in number) . So what it points to from two short partial tests is small Vacuum leak somewhere or leaky EGR or sticky lifter/carboned valve (that 2 inch vac drop miss at idle). Recommend an oil change and a can of berrymans in gas for(#7) with read thru on vac gage diag especially a 60's chart that shows more tests.
Vac diagnosis is valuable in steady state runs usually, as hiccups show. Between your scanner recording live data and a glance at the vac guage occasionally or when you feel a change should generate a solution. Keep posting results and Good luck.

Yeah it seems anytime I am accelerating or at high rpm. The vacuum is extremely low. Someone else recommended I try a leak down test on that cylinder and since you’re saying possible valves or rings I’m more motivated to do the leak down test….
Tough for me to get a good video. I need a co pilot or 2 cameras to record RPMs and the vacuum at the same time. Or just narrate better. But I appreciate you looking at the videos and giving me some input

 

[exp500]

You don't need to video vac gage, just glance at it once in a while. Your scanner should record 10-15 minutes or more .
Again, read about vac diagnosis. Maybe even unplug EGR. ( I'd have to review cautions on that)

 

[Tonyv__]

You don't need to video vac gage, just glance at it once in a while. Your scanner should record 10-15 minutes or more .
Again, read about vac diagnosis. Maybe even unplug EGR. ( I'd have to review cautions on that)

I was searching Just out of curiosity and pricing. Apparently my truck doesn’t have an EGR valve. No matter where I look. Rockauto for example. I can find an EGR valve for a 96 express van. But when I put in 08 express 3500 with 6.0. EGR isn’t even an option in the exhaust section. No luck Amazon. No luck elsewhere. Is it called something else?

 

[OR VietVet]

No. GM did away with egr valves on some engines at one time and continued that way, as far as I know, but changes come and go.

I have no idea why what I found out at RA is what it is but:

2008=no egr valve or gasket
2007=egr gasket listed but no valve
2006=egr gasket listed but no valve
2005=egr gasket but no valve
2004=egr gasket but no valve
2003=egr valve and gasket listed

This is for the 3500 Express Van with 6.0 engine

 

[Tonyrodz]

No. GM did away with egr valves on some engines at one time and continued that way, as far as I know, but changes come and go.

I have no idea why what I found out at RA is what it is but:

2008=no egr valve or gasket
2007=egr gasket listed but no valve
2006=egr gasket listed but no valve
2005=egr gasket but no valve
2004=egr gasket but no valve
2003=egr valve and gasket listed

This is for the 3500 Express Van with 6.0 engine

I just checked RA for an egr for my Express 2500 with the 4.8. No dice, nothing shows, but like you said, they only show a gasket. Doesn't make sense to me. If there is a gasket there--where would it be, and could that be a source of a vacuum leak? I'm curious because I'm still having an issue too.

 

[OR VietVet]

Maybe the gasket is for a block off plate where the egr valve used to be.

Kind of like an oil cooler block off plate.

 

[Tonyrodz]

Maybe the gasket is for a block off plate where the egr valve used to be.

Kind of like an oil cooler block off plate.

Would the egr be on the intake?

 

[OR VietVet]

I read someplace where they were also mounted at back of throttle body but did not pay attention to application when I was looking. I woud just look high and low for where the gasket may fit.

Sorry, gotta go @Tonyrodz, time to drop a deuce. Will be back with clean hands

 

[Tonyrodz]

I read someplace where they were also mounted at back of throttle body but did not pay attention to application when I was looking. I woud just look high and low for where the gasket may fit.

Sorry, gotta go @Tonyrodz, time to drop a deuce. Will be back with clean hands

Take it light Ron

 

[OR VietVet]

It was a double deuce. Had to flush twice. Love me some tacos. I can eat at least 15 in one sitting but pay the next day. At least, unlike your emoji, I have a toilet!

 

[ks03]

@Tonyv__ does it happen to run worse if you park it with the front end pointed up an incline?

just thinking 7 and history of 8, if you have oil puddling in your intake it tends to affect those cylinders

 

[Tonyv__]

@Tonyv__ does it happen to run worse if you park it with the front end pointed up an incline?

just thinking 7 and history of 8, if you have oil puddling in your intake it tends to affect those cylinders

I park in the same spot everyday so I don’t really notice. It seems to be level driveway but if anything it’s sloped toward the street so my front bumper would be inclined down causing oil to go to the front of the motor.

there were s few days I had it on ramps to change transmission pan and fluids. That would be a good incline. I can definitely say I didn’t notice anything to be worse when it came off the ramps.

edit: I also get near all 6 quarts back every 3500 mile oil change too. Idk how much oil I should be losing if there’s a leak/burning somewhere

 

[ks03]

Might have been a little misleading, how I phrased that. I meant while it’s at more of an angle, not necessarily driving after having been at an angle. If there was any puddling in the intake it would exacerbate the issue, because more would run back towards 7 and 8. Accelerating while driving can have the same effect, of moving things back to 7 and 8, but there’s more things going on, an incline could isolate tone potential cause.

depending on how bad or often it acts up it might not take alot of oil to cause it. Intake puddles and oil level could also be mixed with condensation and fuel.

 

[Tonyv__]

hmm. I gotcha. Would I be able to see this if I removed the throttle body and looked inside the intake? I cleaned the TB a few months ago so the gasket should be new enough to remove and reuse? I hope.

also i don’t know if I stated before but the misfire is only noticeable at idle. I can’t tell if I can’t feel it at higher rpms because a v8 has so many other cylinders to pick up the slack or if the misfire isn’t there at higher rpms.

Like for example if I get in my truck and just drive. The code won’t show for days. But I like to warm or cool my truck down. The remote start usually gets the check engine light going because it’s idling for a few minutes or if I spend time sitting in the van the code will come up because I idled too long. So just going off the check engine light I think the mis is only present at idle

 

[Tonyv__]

so I hope I’m not overreacting. But I did a make shift leak test. Cranked cylinder 7 to TDC and hooked up compressed air. It’s hissing through the oil fill hole. Quiet though the TB, exhaust, and antifreeze tank.. However cylinder 8 is doing the same. Didn’t get a chance to check the rest. Free time is at an all time low lately

 

[OR VietVet]

When you say you only notice the miss at idle, that leads me to believe a vacuum leak. Before I go further, I want to know the test results of the other 6 cylinders.

With just the two cylinders having air at oil fill: Piston rings bleed by, cracked head/gasket....etc. ?????


A compression test with dry and wet results would help pinpoint.

 

[Tonyv__]

When you say you only notice the miss at idle, that leads me to believe a vacuum leak. Before I go further, I want to know the test results of the other 6 cylinders.

With just the two cylinders having air at oil fill: Piston rings bleed by, cracked head/gasket....etc. ?????


A compression test with dry and wet results would help pinpoint.

So you’re saying piston rings do bleed by?

the video I watched said to hook up air. And listen to 4 places. Air at TB or exhaust would be a valve problem. Bubbles in antifreeze would be headgasket. Or air at oil fill would be rings. However idk how much air or how little.

im getting in over my head. I might have to schedule with Chevy and stop talking about it.

couple years ago I’d spend unlimited hours ripping this thing apart but right now priorities have other Plans for me. This sucks lol

 

[OR VietVet]

If left on the air long enough and with enough pressure, you can still get slight air bleed past rings because of piston ring gap, but to do that the air has to go back and forth across the rings till that small gap to get past them. If some idiot built that engine before you got your hands on it, did not stagger the ring gaps and lined them up, well that will allow air past them way easier. If the same amount of air is leaking past all cylinders and you can measure it, then they would be equal enough to drive but compression will blow by them. Even on a great engine, there is very very very slight blow by over time and gets in to the oil. Oil change interval time.

 

[Tonyv__]

Found this tiny vacuum leak with a smoke tester. Could this be big enough to cause rough idle/misfire?
Right above cyl 7