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2004 Ford Crown Victoria Misfire

  • clearset
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03 Sep 2019 23:16 #33402 by clearset
2004 Ford Crown Victoria Misfire was created by clearset
Any help with this would be greatly appreciated. I am new to reading wave forms as well, trying to get better. I will attach as much wave for pics etc.. as i can

Misfire is most pronounced around 1150-1250 RPM and tapers off a bit but definately does not dissappear the higher RMP you go. Can hear the misfire through the exhaust (dual) and see and feel the engine shake.
- New plugs around 8 months ago.
- Ultrasonically cleaned injectors while activating them with an injector pulser (same misfire before and after clean). (after cleaning while activating injectors with pulser them can see all 4 nozzle orifices spray , not while under pressure just with residual ultrasonic cleaning solution in them) .
- Fuel trims are very lean (around -18%) at idle and around -7% at 2000 RPM
- hooked smoke machine to intake, found the egr valve leaking from diaphram. I have one on order but in the meantime i plated the egr. No other intake leaks detected
- sprayed brake clean all around the intake manifold with no change in fuel trim or 02 sensor data. Confirmed a change would occur by spraying at air filter first, vehicle reacted as predicted with rich 02 sensor data and fuel trim data.
- steady manifold vacuum at around -21 with vac gauge
- performed a relative compression test and all cyls within 95% and above
- unplugged one injector at a time with vehicle running and random misfire did not disappear.
- fuel rail pressure while running around 266
- Car has no trouble starting cold or hot
- pico scope power balance test doe's not seem to like to work with this vehicle. I do have a two way scanner with this function, it works but shows random misfires from all cyls over time.
- other than the egr (due to it being blocked off temporarily), no dtc's currently

There is an photo upload limit to this forum so i will post a dropbox link to view all 8 snap throttle and 8 injector wave forms ( www.dropbox.com/sh/tgcc4ja0geiywx0/AACG5...4gatjbloMbgG18a?dl=0 ) . Cyl number will be on lower left of computer screen. Note: 10:1 attenuator was used when reading coil voltage.

My assumption is my random misfire is a lean misfire caused by my negative fuel trims. Assuming that is correct, what is causing my negative fuel trim numbers?
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04 Sep 2019 14:07 #33414 by ontheriver
Replied by ontheriver on topic 2004 Ford Crown Victoria Misfire
What's rail pressure supposed to be at?higher than 26.6,I believe

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  • clearset
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04 Sep 2019 14:44 #33415 by clearset
Replied by clearset on topic 2004 Ford Crown Victoria Misfire
hi and thanks for the reply. I was told by a Ford tech that rount 265-269 kpa was normal (roughly 39.9 psi). For the reading i am relying on the cars pressure transducer being read by my scan tool. This year of vic they did not put an inline schrader valve on the vehicle to hook into (in order to save money). I am assuming if there was an issue with the pressure reg that too low pressure could create positive fuel trim numbers and too high and you would get negative fuel trim numbers. I played around by adjusting my fuel pumps duty cycle with the vehicle running and lowered it a lot, came close to stalling and the fuel trim numbers would come down some. I am assuming it is working fine because of this test

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  • cheryl hartkorn
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04 Sep 2019 18:06 #33417 by cheryl hartkorn
Replied by cheryl hartkorn on topic 2004 Ford Crown Victoria Misfire
what codes you getting?? also what are fuel trims at idle? what is maf reading at idle?? check mode 6 data? misfire data?

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