Single misfire event every 3 seconds

Give input on tuning as well as any tips and tricks you may have. Also feel free to share base mapping files for various engine types.
aleksanderk
Posts: 68
Joined: Fri Feb 01, 2019 4:36 pm
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Re: Single misfire event every 3 seconds

Post by aleksanderk »

Long time since my last update.
I came to think about a fouled spark plug that I had a while ago, that I was sure was caused by my cheap and wring plug wires. Replaced spark plug and wires.

Today I started the car up for the first time since my last post here. Fired up nicely, but still misfiring. Decided to disconnect one injector at a time, and listen to how the engine was running.
Cyl. 1, 2 and 3 it obviously misfired because it was only running on 3 cylinders, but the random misfore was still there. Disconnected cyl. 4 and the random misfire went away, just running on 3.

Pulled the plug and it looked decent. A bit wet, and black, but not caked or anything. Tried another plug I had lying around, but then it wouldn't fire at all on cyl 4. Found another one and it ran again with random misfire. Opened up the gap and tried again. No misfires at all! AFR stabilized, and the engine ran smoother than I ever can remember!
Took the car for a test drive, and the misfires came back. Took the plug out and saw that the porcelain was cracked and was covering the electrode. This was a crappy cheap plug.

Off to buy 4 new plugs this week. I feel really stupid for not taking a closer look at the plugs.
The OEM plug is a BPR6ES, but since it's turboed, I run BPR7ES wich is one step colder. Would I get some form of gain by changing to an Iridium plug or some other "fancy" plug, or even just keep the hotter plug that it has originally?
katana
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Re: Single misfire event every 3 seconds

Post by katana »

In my experience, and unless you are using BIG boost, cooler running plugs are not required with turbos! I think this is a hang over from the past when fairly uncontrolled fueling and boost controls were the norm. Modern plugs don't tolerate fouling AT ALL - generally a carbon'd / fuel soaked plug is scrap these days. Modern plugs are designed to run lean and hot so a little extra fuel - for power or cooling - is tolerated but change the plug spec for a cool running one and trouble ensues. Iridium plugs are great in 'lean burn' engines but not so much in 'power' engines - the tips whilst not fouling can glow red hot so promoting pre-ignition / detonation which isn't good with forced induction! IMO - just use the regular plug and - if & when - the plug looks to be suffering, then maybe swap out for the 7's
aleksanderk
Posts: 68
Joined: Fri Feb 01, 2019 4:36 pm
ECU Model: S80 Pro
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Re: Single misfire event every 3 seconds

Post by aleksanderk »

I'm running 1,6 bar/ 23-24 psi of boost. If I change to BPR6ES, how will i know if it's not "right"? Detonation, or just poor performance?
BPR6ES are stock for this engine when it's N/A, or OEM low pressure turbo. (0,3 bar / 4 psi).

If the pros outweighs the cons, then I will try a 6 instead of a new 7. The 7 might even be the reason why I hade to make this thread in the first place?
stevieturbo
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Re: Single misfire event every 3 seconds

Post by stevieturbo »

If the 7's are in and there are no fouling issues....keep using them.

Although 6's would probably be fine too. A lot depends on fuel and actual usage.

Many will say readings plugs can tell you whether the heat range and many other aspects are right....but that is a bit of an art and requires new plugs each run and fairly specific run and shutdown to get a good picture ( 1/4 mile type run )
aleksanderk
Posts: 68
Joined: Fri Feb 01, 2019 4:36 pm
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Re: Single misfire event every 3 seconds

Post by aleksanderk »

It could be fouling that caused my problems. The mixture has been all over the place sometimes, and that might had a negative impact on the plugs.
A new set og plugs are needed anyway. I think I'm going with 7's, and if these problems return I can try 6's.

A big thank you to all of you that have helped me along the way! :D
katana
Posts: 455
Joined: Sun Jan 27, 2013 6:08 pm
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Re: Single misfire event every 3 seconds

Post by katana »

aleksanderk wrote:I'm running 1,6 bar/ 23-24 psi of boost. If I change to BPR6ES, how will i know if it's not "right"? Detonation, or just poor performance?
BPR6ES are stock for this engine when it's N/A, or OEM low pressure turbo. (0,3 bar / 4 psi).?
That's pretty good boost so 7's may be right. Using 6's too hard would show evidence of electrode burning / melting. It could be that a 6 is the right heat rating but the plug design leaves the tip too or under exposed - not all plugs are created equal!
aleksanderk
Posts: 68
Joined: Fri Feb 01, 2019 4:36 pm
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Re: Single misfire event every 3 seconds

Post by aleksanderk »

Sorry to bring up this thread from the dead.
The MOT ran out so the car has been parked since I was active here last. Then life happened, and the car has just been waiting for me in the garage.

I have now redone the trigger wires for the coil. They were terminated weirdly in the ECU connector. No difference, and still misfiring randomly.
I tried to remove case ground with little effect. Maybe the misfire happened more often.
Tried adding another ground from the case to chassis. No difference.
I bought a new coil wich didn't seem to make any difference either.

The coil I got today is an aftermarket replacement coil for Audi OEM 032905106B or 032905106.
I'm starting to think that dwell time might be wrong. But I don't have anything to measure dwell with.
The company I bought the first coil from said to use 3ms dwell.
I have seen the exact same coil at other shops, and they specify MAX 2,8 dwell.
One guy with a Syvecs ECU used 2,9ms@14v and said it worked fine.
On other forums I have seen 2,9 - 3ms. One said 6ms for cranking.

In my map, the dwell is set to 3ms@13v. Interpolated to 4ms@8v and to 2,8ms@17v. The car starts up fine, and the only thing that seems wrong are the random misfires.

Wonder why I'm not bald yet :lol:

EDIT: I forgot to mention that I replaced the in-tank pump, since that was failing. I think I mentioned it earlier in this thread that there might be a fuel pressure drop at times if the pump was going bad and was starting and stopping randomly. Did not change the misfire, but the HP pump under the car went almost completely silent. So one positive thing has come out of this misfire-deal!
Rob Stevens
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Re: Single misfire event every 3 seconds

Post by Rob Stevens »

can you isolate the misfire to a single cylinder? by disconnecting individual injectors one at a time?
I wouldn't get hung up on dwel times, sounds like you have that set just fine,
stevieturbo
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Re: Single misfire event every 3 seconds

Post by stevieturbo »

So it's exactly every 3 seconds ?

Do you have any logs ? Crank/cam errors ? do they coincide with this 3 second event ?
aleksanderk
Posts: 68
Joined: Fri Feb 01, 2019 4:36 pm
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Re: Single misfire event every 3 seconds

Post by aleksanderk »

Rob: I will try this when I get the time and report back to you.

Stevie: No, it's random. At cruising it might feel like it's misfiring with the same intervals, but I can not confirm it.
No crank errors. I have driven the car, and the counter did not increase when the misfire happened. I found a log for you from when I messed around with fueling. Not the best log to check since I was messing with quite a lot when this was logged.
When the engine misfires, I can see a lean spike on my AFR gauge, but it doesn't seem to show in the logs. Goes from 14,5-7 to 15.2 ish.
I'm logging at 10Hz. Maybe I should increase it to catch the little things?
I can log again when not messing with the map.

Link to download log file: https://file.io/Aw9UDfVTelxF (I couldn't upload to the forums)
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