How to diagnose and resolve engine issues using Durametric.

[jb92563]

Got a new Fuel filter, Gas cap, Oil cap rubber seal and spark plugs to install.

I still feel its a vacuum leak so I'll probably recheck the new AOS install for leaks.

I have this feeling that when I removed the part of the AOS that sticks into the engine block the rubber seal from the old one did not come out on the spigot so when I installed the new one perhaps it did not seal properly.

I will pull the new one and get the inspection camera in there so I can see if that is the issue, as I'm not sure what the old one had on the spigot for a seal, but its reasonable to assume something like the new one has, which was missing when I pulled the old one.

[jb92563]

After Replacing AOS, and a new MAF there is still a random hesitation on acceleration.

Here are some graphs of
1) FRA RKAT fuel trims, 2) RPM, 3) MAF
Seems to show a need for a bit extra fuel (lean) but nothing drastic and nothing that would indicate a serious vacuum leak. Blue line does spike every now and then, wonder if thats normal.


After replacing plugs and fuel filter, some improvement but not cured.
Showing a need to reduce fuel trim (rich) a bit, perhaps the replaced fuel filter is allowing the extra fuel now.


Another trace after cleaning the throttle body actuator (E-gas) Seems to work same as before. Seems even more balanced than before. Not Likely a vacuum leak
as it would cause the line to be much higher on the + side above +10 (+ indicates Lean condition being compensated for -5 +5 is very normal from what I have read)


After checking fuel pressure, flow rate and smoke test to check for vacuum leaks. No Leaks, pressure and flow to specs.


The hesitation does not necessarily occur where the blue yellow lines spike. Not sure what those are.

I think the next place to look may be fuel pressure.
I'm thinking that the pressure regulator may not be responding properly and causing a hesitation.

Perhaps the thin vacuum line controlling the pressure regulator is leaking.

[Xcellr8]

Just a few words of encouragement to keep going and thanks for the continued postings. I've got a durametric but know very little about how to use it. Learning more and more thanks to posts like yours. Thank You!