SOLVED: Need help with bogging and misfires, persistent P0171 & P0174 lean DTCs

[Effduration]

Can you please describe your DIY smoke tester and method?

I have a decent compressor-fed "Stinger" smoke tester bought on amazon and on 2 recent occasions, my indie has found vacuum leaks I was unable to find.

[80stech]

If the gauge is slow to respond going up it can be slower going down, or not go down at all under load so that needs to be dealt with to get an accurate picture of the fuel system. Does the gauge drop 5 or 10 PSI instantly as soon as the pump shuts down? More than once were the OP has not done a fuel pressure test before and doesn't know what things should look like get fooled by the gauge/connection. +1 one one the smoke tester, not the most reliable way to prove no vacuum leaks me thinks
++ fuel pressure test includes driving under load with the gauge taped to the windshield, again common thing for a DIY'er to be fooled by not doing properly.

[Bdc101]

OP is your pressure gauge fluid-filled?



It looks like the slow speed is just due to gauge damping that Andrew's gauge may not have had.



If you use it to check the pressure on other things does it respond just as slowly?

[X5chemist]

What's the fuel reading in grams/sec?
Are any intake runners showing signs of oil residue? Mine had a vac leak along the intake seam.

[andrewwynn]

What I'm noticing is the pressure didn't go to 50 until started. Or should hit 50 at key on. If you key off then key on does it go to 50? In any event I'm getting some deja Vu.

It'll take half an hour but no$ to pull the FPR and look at the o-rings. At the age of the car I'll need surprised it's not flattened like mine was

https://youtube.com/shorts/AEjiWbrrP...VEy8TkHUtTdSzm

[victell]

Originally Posted by Factory6speed

…the circular plug for the ignition wire harness wasn't totally plugged in. It was half way in…check electrical connectors.

Ok I checked the connector and wiggled the harness with the engine running, no change.

Originally Posted by Effduration

Can you please describe your DIY smoke tester and method?
… my indie has found vacuum leaks I was unable to find.

I used a version of the smoke machine below. Manually blew smoke into the intake boot just after the MAF. The DIY tester was leaking smoke from the cap and the test area was windy. What method did your indy use to find the vacuum leaks?

Originally Posted by 80stech

If the gauge is slow to respond going up it can be slower going down, or not go down at all under load so that needs to be dealt with to get an accurate picture of the fuel system. Does the gauge drop 5 or 10 PSI instantly as soon as the pump shuts down?… +1 one one the smoke tester, not the most reliable way to prove no vacuum leaks me thinks
++ fuel pressure test includes driving under load with the gauge taped to the windshield, again common thing for a DIY'er to be fooled by not doing properly.

Originally Posted by Bdc101

OP is your pressure gauge fluid-filled?

Originally Posted by andrewwynn

What I'm noticing is the pressure didn't go to 50 until started. Or should hit 50 at key on. If you key off then key on does it go to 50? In any event I'm getting some deja Vu. It'll take half an hour but no$ to pull the FPR and look at the o-rings. At the age of the car I'll need surprised it's not flattened like mine was

I’ve now removed the schrader valve from the fuel rail and adapter, and opened the tester’s purge valve until fuel filled the hose up to the gauge displacing the air making it fluid filled. Previous fuel pressure video was a taped-to-windshield drive but did not do that this time as I couldn’t get a leak-free tester setup and didn’t want to risk it. Response is much faster now, but overall the same. Video below.

Originally Posted by X5chemist

What's the fuel reading in grams/sec?
Are any intake runners showing signs of oil residue? Mine had a vac leak along the intake seam.

I do have oil residue inside my intake (pics below). How would an intake vac leak cause this? For fuel reading do you mean volume test or Foxwell fuel consumption live data?

[Effduration]

Originally Posted by victell

I used a version of the smoke machine below. Manually blew smoke into the intake boot just after the MAF. The DIY tester was leaking smoke from the cap and the test area was windy. What method did your indy use to find the vacuum leaks?

Manually ? You mean like blowing on a hose or something???

To do a decent smoke test, you need 10 minutes + of steady smoke at a steady pressure. and you need to introduce smoke in several locations...like the brake booster...as well as the intake.

My Indy used a professional-grade smoke tester that costs $1,000's...

You need to get a proper smoke test done...I suggest you pay a tech to do one.

[andrewwynn]

That jiggle at isle exactly matched mine with the FPR leak!

After the fix it rests exactly 50.00 and doesn’t waver at all.

That’s the sign I was looking for! 90% certain FPR is your problem. When FPR is working properly the needle should be rock stable at idle.

https://youtube.com/shorts/AEjiWbrrP...VEy8TkHUtTdSzm

[aureliusmax]

Originally Posted by andrewwynn

That jiggle at isle exactly matched mine with the FPR leak!

After the fix it rests exactly 50.00 and doesn’t waver at all.

That’s the sign I was looking for! 90% certain FPR is your problem. When FPR is working properly the needle should be rock stable at idle.

https://youtube.com/shorts/AEjiWbrrP...VEy8TkHUtTdSzm

I recall a video in 2021 I made with my E66 N62 having an unstable fuel pressure like shown above. The FPR is integrated into the fuel filter, but I've since changed the filter assembly. Currently repaired multiple issues on the engine but I will have to check and see if this one is still remaining, and look into the regulator.

[80stech]

OK, I didn't watch the first video before. The gauge does rise on the slow side but also drops when the pump shuts off (pressure drops to regulator setting but should hold there) which is good because it verifies that the gauge will drop with the actual pressure. The second video you start the engine just as the pump shuts off to prime and gauge is dropping. Under load though means highway speed and full throttle if you want to rule out fuel. Are the codes coming back up after regular driving?