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Peugeot 308 1.6 2008 misfire 5FW
Peugeot 308 1.6 2008 misfire 5FW
I was trying to help a friend with this car, as he was struggling for a while with it.
Complaint, engine running rough, misfire reported on cylinders 2, 3 and general misfire code P0300. Plus low fuel level misfires, but that we can safely ignore, as the tank has been later filled, with no change in engine behavior. So far done to the car: cylinder head removed, checked, spark coils, spark plugs, fuel pump, pressure regulator, throttle body and now the ecu was in doubt.
As I am not familiar with the car brand, I brought along the tool I made based on Excel and api to Picoscope, some more details are to be found here: topic22841.html
What it basically does, channel A connected to crankshaft position sensor and channel B to the ignition coil of cylinder 1. It will show the crankshaft speed variation and which cylinder is misfiring, and how many times per capture.
Well, because my excel was prepared for inductive sensors, at that time the data processing showed only garbage, so I left it to be verified somewhere towards the evening. In the mean time, did a relative compression test, and found that:
- one cylinder had good compression
- two identical cylinders with a bit less compression
- one cylinder with about 3 bars less compression than the best.
And we quickly arrived to the conclusion that the lowest cylinder had trouble on the intake valve lifter, which also made lots of noise, so basically not filling or retaining oil in it. So that had to be replaced.
So home I managed to resolve the excel VBA issues, which was simple, I was looking to the crossing point of the signal at 0V, but for a hall sensor, one better looks at the crossing at 2-2.5V. So that done, I processed the data and this showed up, as crankshaft speed:
So I don't know about you, but what's with that speed increase in the same spot, every revolution, it does not seem right. I zoom in, count the teeth and call my friend: Hey, at teeth 21, have a look and verify that the teeth is still in good shape, as I don't understand what am I seeing here.
Few minutes later a call back and he told me: You are not normal. I asked, why? He said, have a look at the picture:
That's fun, how is this possible? He said it might of got damaged at the time of crankshaft locking tool use, in order to do the timing.
Nice, so day later, teeth straighten, lifters replaced, engine confirmed run perfect. So it appears that a sudden acceleration and deceleration of the shaft speed, at least as seen from the ecu point of view, was enough to confuse the ecu completely, and cause these misfire codes.
I can't guarantee that I would of easily seen the anomaly, just by a normal scope capture. I encourage all to explore more options, build own tools and try them out. It's definitely fun. Use data to your advantage. Happy scoping.
Complaint, engine running rough, misfire reported on cylinders 2, 3 and general misfire code P0300. Plus low fuel level misfires, but that we can safely ignore, as the tank has been later filled, with no change in engine behavior. So far done to the car: cylinder head removed, checked, spark coils, spark plugs, fuel pump, pressure regulator, throttle body and now the ecu was in doubt.
What it basically does, channel A connected to crankshaft position sensor and channel B to the ignition coil of cylinder 1. It will show the crankshaft speed variation and which cylinder is misfiring, and how many times per capture.
Well, because my excel was prepared for inductive sensors, at that time the data processing showed only garbage, so I left it to be verified somewhere towards the evening. In the mean time, did a relative compression test, and found that:
- one cylinder had good compression
- two identical cylinders with a bit less compression
- one cylinder with about 3 bars less compression than the best.
And we quickly arrived to the conclusion that the lowest cylinder had trouble on the intake valve lifter, which also made lots of noise, so basically not filling or retaining oil in it. So that had to be replaced.
So home I managed to resolve the excel VBA issues, which was simple, I was looking to the crossing point of the signal at 0V, but for a hall sensor, one better looks at the crossing at 2-2.5V. So that done, I processed the data and this showed up, as crankshaft speed:
Few minutes later a call back and he told me: You are not normal. I asked, why? He said, have a look at the picture:
Nice, so day later, teeth straighten, lifters replaced, engine confirmed run perfect. So it appears that a sudden acceleration and deceleration of the shaft speed, at least as seen from the ecu point of view, was enough to confuse the ecu completely, and cause these misfire codes.
I can't guarantee that I would of easily seen the anomaly, just by a normal scope capture. I encourage all to explore more options, build own tools and try them out. It's definitely fun. Use data to your advantage. Happy scoping.
Last edited by liviu2004 on Mon May 30, 2022 6:32 pm, edited 1 time in total.
Re: Peugeot 308 1.6 2008 misfire 5FW
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Steve Smith
- Pico Staff Member
- Posts: 1593
- Joined: Sun Aug 25, 2013 7:22 am
Re: Peugeot 308 1.6 2008 misfire 5FW
Hi Liviu, thank you for posting and your hard work is paying off already re your excel and PicoScope API
I love that line "You are not normal." Your friend will be singing your praises for years to come
It would be good to see this capture using crank math's and see how this deformed tooth would affect the frequency
Nice work and thank you for sharing
Take care.....Steve
I love that line "You are not normal." Your friend will be singing your praises for years to come
It would be good to see this capture using crank math's and see how this deformed tooth would affect the frequency
Nice work and thank you for sharing
Take care.....Steve