Single misfire event every 3 seconds

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aleksanderk
Posts: 68
Joined: Fri Feb 01, 2019 4:36 pm
ECU Model: S80 Pro
Firmware Version: 6500

Single misfire event every 3 seconds

Post by aleksanderk »

Hi!
I am once again returning here for some advice! You guys have helped me fix a lot of small issues :D

The problem this time (Or since the beginning really) is that I have a very subtle misfire that happens about every 3-4 seconds. If I hold the car steadily on 2k rpm if you could just barely feel it. It is easier to hear it than to feel it in the car. It's like it misses one cylinder firing event.
When driving I can feel it to. The car is jerking a tiny tiny bit. The RPM does not seem to affect how often it happens, but it might happen a bit more often at higher RPM.

I use a KMS Discoil wasted spark coil, that I think is a copy of an original Audi wasted spark coil. This coil is externally amplified.
Dwell time is set at 2600
Engine is a Volvo B230FB with a turbo added. 4 cylinder inline 2.3L. Single cam.
BPR7ES spark plugs.
9,5:1 compression ratio
Around 1.2bar of boost.
DTA S80 pro

I don't belive that the dwell time is too low, since I don't have any increased misfire on high load/high boost. I tried lowering it until a noticeably misfire on idle, but didn't hear any misfire even at 800 dwell. Should have tested with load.

Any tips? ;)
stevieturbo
Posts: 3577
Joined: Tue Aug 02, 2011 12:08 pm
ECU Model: No ECU
Location: Norn Iron

Re: Single misfire event every 3 seconds

Post by stevieturbo »

Is the ecu case earthed ?
aleksanderk
Posts: 68
Joined: Fri Feb 01, 2019 4:36 pm
ECU Model: S80 Pro
Firmware Version: 6500

Re: Single misfire event every 3 seconds

Post by aleksanderk »

Yes. Grounded to a chassi ground approximately 40cm from the case. I could try to sand the grounding points if that might help.
stevieturbo
Posts: 3577
Joined: Tue Aug 02, 2011 12:08 pm
ECU Model: No ECU
Location: Norn Iron

Re: Single misfire event every 3 seconds

Post by stevieturbo »

aleksanderk wrote:Yes. Grounded to a chassi ground approximately 40cm from the case. I could try to sand the grounding points if that might help.
Generally it would use same ground as main power ground.

And all earthing points should be to bare metal.

If it has an earth at present...could try removing the case earth ?

Although when the S80/S series first came out, mine was one of the first ecu's to have a misfire problem due to no case earth ( no provision to earth them back then )

Mine was a random miss when driving off from idle, and during light cruise. But seemed ok the rest of the time. Earthing the case resolved it.
Rob Stevens
Posts: 1247
Joined: Thu Jul 28, 2011 4:10 am
ECU Model: S100 Pro
Distributor: None-Coil On Plug :)

Re: Single misfire event every 3 seconds

Post by Rob Stevens »

log at high data rate to see if you can see anything odd there. Is closed loop fuelling doing something perhaps?
aleksanderk
Posts: 68
Joined: Fri Feb 01, 2019 4:36 pm
ECU Model: S80 Pro
Firmware Version: 6500

Re: Single misfire event every 3 seconds

Post by aleksanderk »

I drove the car today without my laptop connected. I did not react to any misfire when driving, although I was not really aware of it either.
Had it warming up a bit and stood behind the car to listen for misfire but it ran super smooth today.

Could it be that when the laptop is connected, something messes up? Sometimes the map crashes completely when saving with F4. Recently the Main map RPM coloumns got messed up when saving, and earlier the Start fuelling got set to around 600% when saving. Or could this be a grounding issue as well?

One of the grounds from the connector goes to the ground pin on the case, and then to a chassi ground. The chassi ground is shared with main power relay ground. I will try to clean that ground anyway.
Alex DTA
Posts: 1622
Joined: Fri Feb 28, 2014 1:03 pm
ECU Model: S40 Pro
Distributor: DTA
Firmware Version: 79

Re: Single misfire event every 3 seconds

Post by Alex DTA »

If you have weird issues with a laptop plugged in, you generally have an earth issue somewhere, and the ECU is grounding back through the PC.
aleksanderk
Posts: 68
Joined: Fri Feb 01, 2019 4:36 pm
ECU Model: S80 Pro
Firmware Version: 6500

Re: Single misfire event every 3 seconds

Post by aleksanderk »

That's what I was suspecting. I've noticed a small flicker from the headlights when driving at night, so I'm guessing it's tie to do a clean up of all the grounds on the car. I will keep you updated!
The last couple of times I have driven the car it seems much better. But it's been dry thome times, si it seems like there is a ground issue somewhere. Dang old Volvos :lol:

As a side note: I use closed loop on the ECU and it behaves a bit funky. The ECU reduces fuel "live" by 5%, but sometimes the correction map says to increase by 3 for example. Just the nature of the beast, or me doing stupid stuff again? :roll:
Max increase/decrease is set to 5%. PID is 350/10/10 after reading the forums, but was originally 200/0/0 Little difference after changing PID.
Rob Stevens
Posts: 1247
Joined: Thu Jul 28, 2011 4:10 am
ECU Model: S100 Pro
Distributor: None-Coil On Plug :)

Re: Single misfire event every 3 seconds

Post by Rob Stevens »

So what happened when you logged it? Was the voltage stability poor.
aleksanderk
Posts: 68
Joined: Fri Feb 01, 2019 4:36 pm
ECU Model: S80 Pro
Firmware Version: 6500

Re: Single misfire event every 3 seconds

Post by aleksanderk »

Rob Stevens wrote:So what happened when you logged it? Was the voltage stability poor.
I have not done any logging yet :oops:
I will try to log before and after cleaning the grounds. Will update you here, to help others as well :)
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