Random aggresive Misfire
 

Can anyone please tell me what's going on here?
I'm supercharged (harrop with 700cc injector on 93 - straight pipe)
Just driving to work ..and I get the flashing engine light (with trac off) and vehicle shaking. I stopped immediately to the side and checked with my ecuktek App. It turns out I have a p0303 - misfire in 3rd cylinder.
Now I've been having some misfire during idle util it settles down for a while now but this one is very different.
Anyway looked around in the engine bay ..nothing unusual (although I do smell fuel - no surprise there). THe spark plugs and coil was changed earlier this year, although i will admit the coil was an ebay brand ones (non-oem) so I'm not sure if that makes any different. Infact the reason why I changed that was to address to misfire when it idles during cold start - it's worse when the weather is cooler.

Anyway I started the car again and it's fine. I drove below 3k rpm to work.
Later on after work, started it and the dreaded misfire continues. Now at this point, it was already too late , so i drove the car slowly as i can below 2k rpm along local street while i continue to log the data. And then sometimes the misfire just..stops and then after a while it kicked in rapidly again.
Can anyone chime in on what's happening here (keep an eye on the main culprit (Cylinder #3 misfire):
Log: https://datazap.me/u/ojuniour/flashing-engine-misfire-p0303?log=0&data=15-19

I'd vote to replace non-oem coil with OEM coil.

where did the spark plugs come from? there's a number of recent cases where plugs from amazon or ebay are fakes, which can also cause problems. the best place to get plugs is going to be over the counter at the dealership anymore...

+1 for the aftermarket coil, especially with supercharged tuning. but high skepticism on the plugs used

Well, I got it from ebay:

https://www.ebay.com/itm/33476429627...mis&media=COPY

I have since changed out the cylinder #3 coil with one of the OEM I took off.

Now I don't have that crazy misfire.. except for like 1 or 2 misfires when I quickly tap of the gas (literally feathered the gas for like split seconds)..I sometimes get couple of misfire on #3 and none or once on the rest of the cylinder.. That has been happening even before I made all these changes and also prior to FI. SO I'm not sure if the fuel pump is dying or something. :iono:

It could be a fuel injector starting to fail.

Agreed. Swap the two port fuel injectors on that one side to see if the problem moves to cylinder #1. That would be the quick, easy check. Be careful, those injector holes are machined very sharp and can easily cut the injector O-rings. Lube them with fuel or a light film of mineral oil and make sure you push them in perfectly straight.

Let us know the result.

P.S. How many miles on the car?

I got the injectors used with the supercharger.. don't quite remember how many miles was on the injectors (dw700cc) .
I will swap injectors around to see how it goes.

Car is 85k

Alright.. still samething.. I mean it was doing before I changed the coils and sparks anyway.. it has just gotten worse overtime.

Interestinging thin gi didn't mention was that during idle..when the rpm keeps oscillating way below 1k rpm (causing misfires) and most of all (when fully warmed up). If I lightly press the gas for like split second, the rpm drops and i get misfires. And if I go full WOT usually between 2 to 3rd.. at the peak redline.. Fuel just cuts off and would pick bac up after like 4 to 5k rpm. That happens 90% of the time. And for example to do a 0 to 60.. I would have to not fully go WOT ..maybe like 80% throttle to prevent such phenomenon.

I v'e checked for leak..none. Only think I haven't done is compression test.
Now do you think something is wrong with the fuel pump, regulator, filter?
What's the best parameter to watch for anything relating to fuel pump?
Here is a log of the (sorta fuel cut?) issue at WOT:

https://datazap.me/u/ojuniour/85mm-pull-fuel-cut?log=0&data=27
please help :(

btw I couldn't even pass NJ inspection because of "Fuel System - Unsupported"> Perhaps that's a separate issue (or it could be related). My tuner doesn't know why that is either.

I guess no one has any idea.. Anyway I think I might be getting close. I'm gonna be updating just for anyone who might run to similar issue in the future.
I had just replace the [low pressure] Fuel pump.. same result.
I am now noticing that DI pressure is sporadic..way below the standard 4mPa at idle. it jumps and goes as low as 1.3 to 3.8.
I'll be replacing that and see if that's the issue.

Alright update:
I just replaced the DI's High Pump Fuel Press (Hpfp).
Same thing.
The car now taking long to crank (AUTO btw),
The misfires when the DI kicks in..causing surging.
The almost stalling at load (especially going uphill.
The random ACTUAL stalling when trying to accelerate.
Car powering off when not moving (sitting at idle) for a while..like 8 to 10 mins ish.

This is starting to pointing to the elephant in the room.
It can't be the battery though because when it stalls and just dies.. All the lights are still working (including the Headunit).
All these points to one thing:
Alternator going bad? Not supplying enough current to ECU in relation to the sparks and Direct injectors (among other fuel related stuff) not getting consistent power?
OR
just a bad ground.

I'm going to test the battery later.

But that's just food for though. Anyone else want to chime in if this makes sense.

I mean I've replaced sparks, the whole fuel pump (new pumps/filter), coils, and hpfp.

I've also obviously checked for vacuum leaks using smoke detectors..

Only thing i haven't done is compression test..but these symptoms doesn't scream that.

And now I've arrived at the alternator/bad ground. Unless the gods! have cursed my car. :(

Have you tried disconnecting both battery cables and holding them together for a bit (hard reset)?

i would drive it with a volt meter installed to monitor voltage, if that's where your suspicions are leading.

Haven't touched there battery terminal together.. will give that a shot.
I have the mid refresh so I can monitor the voltage in realtime in the dashboard. I also have the ecutek app keeping track of it also among other parameters on my head unit...

Ok minor update:
I'm being told it could be the crank position sensor.. so I will probably look into that.
The location seems PITA though ..(below the harrop supercharger manifold.. yikes)

Ok minor update:
I'm being told it could be the crank position sensor.. so I will probably look into that.
The location seems PITA though ..(below the harrop supercharger manifold.. yikes)

Update:
I just bought a new crankshaft position sensor.. took out the old one. I haven't installed it yet. But checking the ohms on the old generates nothing- literally no signal , while the new one gets me about 6.9ohm.
And the magnetic force on the old one is MUCH weaker compare to the new one.
This could be my culprit all along. I'm gonna install it in the next coming days. Wish me luck