Engine Stumble with odd O2 readings
#41
#42
If I'm understanding you correctly the drop in the fuel pressure sensor reading only occurs with the "blip"
If that's correct it is a not related to your issue as the reading is relative to vac. If the engine "blips" you will get a vac change causing the reading. I very much doubt you would see any change with an actual fuel pressure gauge on the rail. Ie an absolute reading rather than relative.
If that's correct it is a not related to your issue as the reading is relative to vac. If the engine "blips" you will get a vac change causing the reading. I very much doubt you would see any change with an actual fuel pressure gauge on the rail. Ie an absolute reading rather than relative.
Originally Posted by XJ8JR
Did you ever check out the 02 sensors?
#44
So your suggestion is fix the grounds, replace the O2 sensors, let it relearn and see where it stands?
#45
The ones to upgrade are G1, G2, G3 and G26 (LHD) / G30 (RHD)
The ones that could be effecting your issue are G2 and G26/30
G2 has the slave Ign Relay & O2 Sensors
G26/30 has the Ecu + sensors & Ign Coils
After that see how it goes
Also do a quick check of the exhaust pipe bolts where the pipe meets the manifold. You can get to then from under the car and its a good source for unmetered air.
Cheers
34by151
#46
Update: a couple months continued with the intermittent stumble, no new symptoms/codes/issues, just the annoying very intermittent stumble. I finally decided to gamble on my original instinct and replace the FRP sensor based on the dropouts I was seeing in scan data. Also, the realization that the "random" nature of the issue had a feeling to me of a bad solder joint (I can see that the FRP sensor has some electronics in it, as it's a vacuum-pressure transducer, which is epoxy potted).
The FRP pressure sensor made an immediate and marked difference in the engine running. Been about a week and 200 miles, including one long trip (70 miles), I think this finally fixed it. It has seriously changed the way the engine runs (for the better). Smoother shifts, torque off the line under normal acceleration, no more stutter/stumble. Waiting a few more miles and will check to see how the LTFT have adapted.
After a few more weeks when I'm 100% sure that the base issue is solved, I think I'll go ahead and replace the O2 sensors and maybe the knock sensors to give the engine a refresh. It doesn't surprise me in the lease that the sensors on top of the engine aged/failed in such a harsh environment with so many heat cycles.
The FRP pressure sensor made an immediate and marked difference in the engine running. Been about a week and 200 miles, including one long trip (70 miles), I think this finally fixed it. It has seriously changed the way the engine runs (for the better). Smoother shifts, torque off the line under normal acceleration, no more stutter/stumble. Waiting a few more miles and will check to see how the LTFT have adapted.
After a few more weeks when I'm 100% sure that the base issue is solved, I think I'll go ahead and replace the O2 sensors and maybe the knock sensors to give the engine a refresh. It doesn't surprise me in the lease that the sensors on top of the engine aged/failed in such a harsh environment with so many heat cycles.
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