Fuel filter vs vacuum leak

[my dreamt dsm]

I've been searching online the whole night. The problems seems very similar. Anyone has a certain experience that could narrow my problem.
At idle I'm holding a steady 17hg. I've been reading that bad fuel filter could cause hesitation, poor gas milage, bucking etc.
With logs of evoscan I notice I've been running very lean which cause my CO to go up, causing me to fail smog.

 

[XiKeiyaZI]

Well, the easiest way to narrow your problem down between it being a Fuel Filter or a vacuum leak would be to get a can of starter fluid and spray it around your vacuum hoses. Listen for an increase in idle. If you find nothing then why not go ahead and simply replace the fuel filter? They're only a few bucks and the worst part is the damn screw on the bottom of the filter unless you've already addressed that.

I'd recommend soaking it in penetrating oil for a bit before messing with it.

 

[Diamond Star Werks]

User your data logger and watch your 02 readings. Spray areas that could have vacuum leaks. If there is a leak the 02 should read rich whenever out sucks in the starter fluid. That'll show leaks not large enough to change idle.

Vacuum leak is also a boost leak, so if it is a vacuum leak, it should be lean in vacuum and rich during boost. A clogged filter will read constant lean and get worse with boost.

When removing fuel filter, usually bad ones will dump dirty gas out inlet and clean out the outlet. you can also try blowing through it. Itll be difficult to blow through if its clogged.

 

[DEADKITTY]

Why not just go ahead and try and change the fuel filter they are cheap and if that doesn't fix the problem then you will know for sure that it is a vacuum leak.

 

[my dreamt dsm]

Seems stupid but when I have time. I'm going to use thick hookah smoke and blow it into the manifold blocking off the throttle body to see where smoke comes from. Sounds dumb but I know it should work.
After the freebie Ill go ahead and change the fuel filter. After many nights of contemplating if it is it. My theories lead the fuel filter.

 

[Diamond Star Werks]

Seems stupid but when I have time. I'm going to use thick hookah smoke and blow it into the manifold blocking off the throttle body to see where smoke comes from. Sounds dumb but I know it should work.
After the freebie Ill go ahead and change the fuel filter. After many nights of contemplating if it is it. My theories lead the fuel filter.

Itll work, actually have a machine that does that at the shop. Lol neat lil thing.

 

[CleverDSMusername]

User your data logger and watch your 02 readings. Spray areas that could have vacuum leaks. If there is a leak the 02 should read rich whenever out sucks in the starter fluid. That'll show leaks not large enough to change idle.

Vacuum leak is also a boost leak, so if it is a vacuum leak, it should be lean in vacuum and rich during boost. A clogged filter will read constant lean and get worse with boost.

When removing fuel filter, usually bad ones will dump dirty gas out inlet and clean out the outlet. you can also try blowing through it. Itll be difficult to blow through if its clogged.

MJcanada is right, i had a chevy silverado 2500 come through my shop a lil while back for an intake gasket leak & after getting it back together it ran a tiny bit rougher than before so me & my boss checked for vac leaks with carb cleaner only to find nothing, so then we threw a new fuel filter on it & it smoothed up a bit. after lunch that day we checked the ignition timing & o2 readings with our scanner via datastream, timing was a bit off so we corrected that & idle improved more but not enough so he sprayed again while i watched the readings & it ended up having a plastic vac line with a small pinhole but couldn't replace it since we was unable to get a replacement line he just turned the distributor CCW as far as he could turn it & locked it down & that fixed it (might've even improved power a lil bit, i drove it the last time we worked on it & it definitely had more power than befor after he adjusted that distributor).