SOLVED: Another misfire chasing threads (2008 express van)

[Tonyv__]

Intake is where to start for sure. Any vacuum hoses in the area.

There’s a vacuum hose on the valve cover directly above cylinder 7. Seems tight. But I’ll check it out. I’m gonna make a makeshift smoke tester tonight

 

[OR VietVet]

Yea, could be as simple as that hose.

 

[Tonyv__]

So nothing on the smoke test. And I used carb cleaner all around cylinder 7 and any hoses I could see. Nothing noticeable. I even pulled the hose off the valve cover and there was a noticeable difference when I did that. Put it back on and the engine went back to semi normal…. I’m gonna try a noid light for the fuel injector. If that doesn’t show me anything. I’m at a loss. Might have to cave into a mechanic

 

[Rocket Man]

So nothing on the smoke test. And I used carb cleaner all around cylinder 7 and any hoses I could see. Nothing noticeable. I even pulled the hose off the valve cover and there was a noticeable difference when I did that. Put it back on and the engine went back to semi normal…. I’m gonna try a noid light for the fuel injector. If that doesn’t show me anything. I’m at a loss. Might have to cave into a mechanic

Well that sucks. I don’t have any further suggestions other than it could still be an intake leak. I have done a smoke test on my 02 and can’t find anything but I know it’s leaking according to Blackbear and the fact it randomly throes P0300 random misfire. I can look at live data and see lots of misfires on #4 & #5 but can’t find the leak. I am running a Whipple blower but it shouldn’t matter, the smoke should show it but doesn’t. I guess it could be internal between those 2 plenums but wtf. I’ll be following your progress.

 

[Tonyv__]

Well that sucks. I don’t have any further suggestions other than it could still be an intake leak. I have done a smoke test on my 02 and can’t find anything but I know it’s leaking according to Blackbear and the fact it randomly throes P0300 random misfire. I can look at live data and see lots of misfires on #4 & #5 but can’t find the leak. I am running a Whipple blower but it shouldn’t matter, the smoke should show it but doesn’t. I guess it could be internal between those 2 plenums but wtf. I’ll be following your progress.

I just bought an autel handheld today but of course I didn’t check. I need a windows pc. So now I’m in the process of installing windows on my mac. Then I’ll get the handheld running then I wanna watch my live data and see if the mis is consistent or goes away at certain rpms. Don’t know what that’s gonna tell me but I’m not giving up just yet

 

[Tonyv__]

Tried a noid light on the fuel injectors. They checked out fine. Really hoping it’s nothing internal. “Fingers crossed”. But I imagine compression test should of shown that. The search continues

 

[exp500]

Do you have an accessible place to add a tee to get a good vacuum reading you could watch driving? Old school but very accurate on a chase. Look for a 1960's vacuum diagnostics chart. Hopin for an easy fix, Good Luck!

 

[Tonyv__]

Do you have an accessible place to add a tee to get a good vacuum reading you could watch driving? Old school but very accurate on a chase. Look for a 1960's vacuum diagnostics chart. Hopin for an easy fix, Good Luck!

I don’t see why not. Especially because you service the engine from inside the cab. I could put a T on the vacuum line going to the valve cover and mess with that while driving

On another note I dropped the van off today to a mechanic my dads been going to for years. They seem to think I have a “strong motor” and also can’t find any leads other than the PCM might be the culprit. They don’t have a tech 2 and suggested I take it to a Chevy dealer to have it diagnosed.. now I’m wondering if I should just gamble with a pcm company i found for $149 already programmed to vin and shipped before I take it to the dealership. Because if the dealer tells me it’s the PCM. I’ll be paying diagnostics fees and probably a grand for a GM PCM.

 

[Tonyrodz]

I don’t see why not. Especially because you service the engine from inside the cab. I could put a T on the vacuum line going to the valve cover and mess with that while driving

For me to get that center hump out I gotta pull the passenger seat--plus all of the other crap between the seats lol.

 

[Tonyv__]

For me to get that center hump out I gotta pull the passenger seat--plus all of the other crap between the seats lol.

My passenger seats been out for weeks now until I have this problem under wraps. I’m tired of it taking 15 minutes to get to my engine lol