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Engine misfire

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2 years 8 months ago - 2 years 8 months ago #50166 by devon 123
Engine misfire was created by devon 123
Engine misfire under high temperature and full throttle. Fault codes are attached,with picoscope mange to take injector no-7 wave pattern and injector no -1 wave pattern.During the test drive cylinder no 7 misfires.Igntion coil ands park plugs swap but only cylinder no 7 misfire.Compression checked its fine. Please can you explain this injector no 7 wave pattern and injector no 1 wave pattern.Capture no-1 is injector no-7,capture no-2 is injector no- 1
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Last edit: 2 years 8 months ago by devon 123. Reason: new information

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2 years 8 months ago - 2 years 8 months ago #50167 by Hardtopdr2
Replied by Hardtopdr2 on topic Engine misfire
According to data your engine temp sensor reads -36 C when ambient temp reads 98.25 C. I think your misfire is in parts a result of the ECT sensor. so you might want to start there for your misfire as it is part of fuel calculations after this injector issue. those injector patterns do not look good. the voltage pattern should go from 12~ volts to near zero for about 3 ms then spike upwards and drop down in a arc. also the amperage waveform is really weird typical waveform pattern for injector is a 45 degree slope upwards to a plateau then drop straight down to 0 amps. this almost looks like a open in the coil winding but with it dropping well into negative amps makes me wonder if amp clamp was on backwards.
Last edit: 2 years 8 months ago by Hardtopdr2. Reason: more data

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2 years 8 months ago - 2 years 8 months ago #50168 by jreardon
Replied by jreardon on topic Engine misfire
I think that's a "piezo stacked" type injector as Bernie calls them. I first heard about it in one of his videos where he says you can't do an injector flow test on a piezo stacked injector.
@25:30

THere's a great write up on diag.net titled 2008 BMW 335i Piezo Injector Waveform Explained @ diag.net/msg/m24kwemdkz7m2ekc56s01fhgnm
Besides that I know nothing else about them really :(

www.motor.com/wp-content/uploads/Gasolin...ection-July-2009.pdf

Piezo injectors have stacks of piezo disks inside. When shocked by high voltage, the disks change their shape—kind of like a flat disk turning into a potato chip shape. This lengthens the overall stack and forces open the injector valve

Last edit: 2 years 8 months ago by jreardon. Reason: another link
The following user(s) said Thank You: juergen.scholl, Hardtopdr2

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2 years 8 months ago #50169 by Hardtopdr2
Replied by Hardtopdr2 on topic Engine misfire
That very well could be thanks jreardon

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2 years 8 months ago #50185 by Hardtopdr2
Replied by Hardtopdr2 on topic Engine misfire
I scrolled through that article and the amp wave form is different in the first part of the waveform it climbs upwards and in your waveform it drops so some food for thought. Has me leaning towards injector issue with the ect issue

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2 years 8 months ago #50186 by Hardtopdr2
Replied by Hardtopdr2 on topic Engine misfire
Actually scratch that the document I downloaded from that article shows a inverted piezo injector waveform though it's from a outside company versus a manufacturer but should still have valid use in this case. Very informative

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2 years 8 months ago #50187 by juergen.scholl
Replied by juergen.scholl on topic Engine misfire

 the amp wave form is different in the first part of the waveform it climbs upwards and in your waveform it drops so some food for thought. 
This is probably just a polarity thing, amp-clamp wise. The overshoot at the end of the reversed current flow and the overall signature is typical for a piezo-type injector

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