Single misfire event every 3 seconds

[stevieturbo]

How many events would there have been on that log ?

I see you're logging "cranke", I presume this is crank errors ?
there is an event there at 721s

Nothing looks out of the ordinary though. If it is that bad, I would think even at 10Hz it should show up. Can you make it missfire, or is it totally out of your control ?

[stevieturbo]

What are valve clearances like ? I presume there is some form of manual adjustment ?

[aleksanderk]

I don't know to be honest. If I get the time tonight, I will log again, and try to count all the misfires I can hear, so it might be easier to find a pattern.
I can not make it miss like this on purpose.

Valve clearance was inside allowed spec when rebuilding the engine. If anything it should be on the looser side. Not many miles on the car since that. No lifter tick that I can hear, but the injectors are a bit noisy.

[craig903]

I had a similar issue. I was having my car mapped at Track N Road in rainham essex and light thotttle 1500-2000 there was a missfire. We tried the usual, swapping injectors and plug leads to see if it swapped cylinder and it didn't untill I swapped no.3 injector plug with no.2 and then it swapped cylinder. I then ran a new wire from the ecu to the injector plug and it still misfired on that cylinder. I had the ecu sent off to dta and they told me its fine but there was heat evidence on the board from when I had set the coil setting wrong. I insisted that the board be replaced anyway because i had exhausted all other options and once it was back in the car on the rollers the issue was resolved. it ran fine for a while and I decided to have the engine out to work on the car but now I'm getting cyl 2 and 3 plugs fouling and missfiring. cyl 1 and 4 are fine I havent looked to hard yet so i'm sure I'll find something.

[aleksanderk]

I have attached 2 logs.
About 20 misfires in each log. Some are noticable by ear and the car is shaking a bit. Some of them make a small subtle backfire in the exhaust. A litte pop.
I tried to capture this on camera, but I will have to review the footage.

Tried unplugging injectors on at the time, but the misfire was present on all 4. So on top of being a random misfire, it's also random cylinder.
If I can find my feeler gauges I will check the gaps on the plugs.

[aleksanderk]

I took the plugs out. Didn't find my feeler gauges. The gaps looked a little bit small, so I opened them up a bit, but the misfire is still there.

I shot a video of the engine, and you can both see and hear the misfire at 35s and 45s.
Link to YouTube:

Also, Closed loop is turned off for the logs in my previous post.

Sorry for the belt noises. Got new ones on the way

[stevieturbo]

And does it drive ok, or is this just at idle ?

[aleksanderk]

The misfires can be felt when driving. Since the MOT hase gone out on the car, I can not test at this point in time. Previously the car was bucking when driving, because of the misfires.

[stevieturbo]

On the second log, there are a couple of lean events. I presume these correspond with your problem ?

The second certainly goes pretty lean, into the 17.x range. But injector pulse is steady, only oddity is both times, idle speed rises just a tad, timing drops when it happens.

But those two change are very small.

You appear to have some form of idle control on, or at least the timing is varying a bit at idle. Can you turn it off, flatline any numbers around idle, to see if a static value of timing at idle makes any difference ?

Have you any means of actually testing spark ? scope, ignition tester, other ?

[aleksanderk]

I took a look in the ignition map, and something has happened there. Most likely my own fault when adjusting fueling.
Ignition should be 14 degrees on idle, but one cell was set to 28 degrees.

3 wire idle valve is installed, and wokring good. I can try to disable it to test if it might be that one causing problems.

I think that those spikes to 17 AFR is when the cooling fan kicks in. Havent figured out how to deal with that yet.
When the misfires happened yesterday the car was idling around 12,2-12,5 and spiked to 12,9-13 when misfire event happened. It happens so fast that it barely registers on the gauge.