I'm trying to confirm that an H3 (I5 5 cyl) with no engine issues should in fact be generating vacuum from BOTH PCV valves and not just the one that feeds into the intake manifold. I continue to track down the cause of my ongoing startup issue where my 2008 starts up fine but then loses power and RPMs rapidly and either dies or nearly dies unless I stay on the gas for ~10 seconds at 2,500RPM. Been happening since 2014 and I've documented it in numerous posts here as well as on YouTube. I'll post a link below to my video of this exact issue.

Referencing the Oil sucking out PCV? post from January 2021, @Doc Olds says 70% of the vacuum comes from the PCV that feeds into the manifold and the rest is handled by the valve that feeds into my Air Doc Intake tube, or what would have been the air box that sits on top of the valve cover. Following a recommendation from a comment posted on my YouTube video below, I blew out both baffles with some carb cleaner today. Never really had issues with oil leaks around the valves like he was having, but our problems seemed to be the same and I've replaced just about the same parts as this guy had before he used the carb cleaner which fixed his problem. Cranked it back up after it was all done and it definitely struggled to start, much more than normal but once it did, it idled and ran fine. Thought it might just be an anomaly since I was just messing with it. Figured I would check the vacuum by removing the hoses just for the hell of it and what I found was the baffle with the hose feeding into the manifold had what I would assume is normal vacuum pressure, but when I removed the hose leading to the Air Doc tube, there was no suction at all. I tried listening, putting the tip of the hose over the baffle, and putting my bare finger over the hole in the baffle am I'm confident that there was no vacuum. Is this the expected result?? I just want to confirm that there should be some amount of vacuum felt/heard when removing the hose from the baffle.

I also will mention that I have no codes other than P0420 for a bad cat (hope to replace the rear cat within the next two months finally) and removing the hoses did not have any impact on the idle. I've also used the propane method to try and find a potential vacuum leak but haven't had any luck, which makes sense to be because I don't have any idle or surging issues other than at the very start (most starts). Feel like I've been running out of options but this new discovery on the lack of vacuum from one PCV baffle has me on a new path. Any ideas?

 

Air intake restriction.

 

Would you be able to elaborate a bit more on possible causes for the restriction? I’m not quite sure how to go about increasing the airflow and why a restriction would only seem to be present at startup. Why would that not also occur at idle? For the record and related to air intake, I do have an aFe Pro air filter (problem also occurred with OE filter, K&N filter, and K&N CAI system), Air Doc, new MAF, and a clean TB. That’s one thing in particular I haven’t thought about changing and simply cleaning, although I would love to order a ported throttle body.
I’ve put more thought towards issues with expelling the air/gases such as the burned catalytic converters, O2 sensors, vapor canister purge valve, etc. for some reason.

What’s interesting to me as well is the startup issue seems to have gotten more frequent and harder to power through by just holding the accelerator around 2,500 RPM ever since I replaced the fuel injectors a few months back. I’ve made sure that the manifold bolts are tight but I just wasn’t expecting the issue to progress and for there to be a smell of gas when starting. I feel like that’s the tell tale sign of a leak somewhere but it’s like one step forward and two steps back every time I try to get to the bottom of this issue. It’s driving me crazy but damnit I just love my H3 so much! Even though they don’t seem close to figuring this out, I’ve learned more than I could’ve ever imagined about cars and engines because of this rig and this forum. Greatly appreciate (most) everyone’s opinions and willingness to help.

 

if you smell fuel then maybe you have a leaking new injector in one of the cylinders.
check to see if your fuel rail is holding pressure with a fuel pressure gauge after pressurizing the rail.
if it drops quickly then either a injector is leaking maybe flooding the cylinder causing hard start or the fuel regulator is not holding pressure
a cut or improperly seated fuel injector o ring can also allow un metered air into the intake that the MAF sensor is not calculating for.

 

I would expect very little/almost no vacuum from the intake at idle.

H3s have no PVC Valves.

If you are smelling fuel, then you have a leak or fuel injector issue.