Strange issue - looking for suggestions - Possible DI or Coil pack problem

[sfruski]

Issue: At a 2500rpm cruise 4th, I can get the Ecutek log to show missfires. It can show up in any cylinder. NO cel!

I have two tunes for the car, in the newest tune you can easily feel the missfires, or what I am perceiving to be the missfire. As you are driving you feel a slight buck and the exhaust note changes. In the older tune, you can't really feel it, but the missfires show up in the logs. (The car is too loud so I don't hear anything other than intake sound from the front of the vehicle.)

I have just pulled all the direct injectors and the seals seem to be fine.

Does this sound like a coil pack or direct injector issue? Or something else?

Early 2013 FRS
Jrsc - small pulley
Ace header and midpipe.
Streetlight flywheel
Fluidamper crank pulley
Tons of other mods, but probabaly not relevant.

[Anderzz]

I literally had the >exact< same issue with an almost identical setup.

JRSC, HKS EL (catless all the way back), Fluidampr, 700cc Injectors, DW300 Fuel Pump.

Between 3k and 3.2k I would 'misfire' under anything more than 50% throttle. No CEL, would immediately resume normal operation after the buck.

I had my coilpacks and plugs done less than 10k ago so looked for other failure points knowing it wasn't that. Talked with Zach at Delicious who is my tuner. Originally we thought it was a vac leak, fixed any/all vac leaks that there were but it didn't fix the issue. He didn't know how to resolve the issue from there but after blind-firing some changes we managed to debug it.

That said, ever since that resolution the car has been producing noticeably less power, and pulling timing, despite the logs looking otherwise good.

Zach's only explanation for the current issue was DI seals but the fact that you're having issues with good seals makes me a little concerned.

Who are you tuned through?

[sfruski]

I am assuming I have good seals, but now that they are out I am replacing them. They might be deforming under heat. I am also changing to a 2015 engine harness and the 2015 coilpacks. Everything should be done in little over a week as long as I get the parts.

I have a delicious tune. I just want to make sure I am not overlooking anything as this vehicle is a race car.

[Anderzz]

Originally Posted by sfruski

I am assuming I have good seals, but now that they are out I am replacing them. They might be deforming under heat. I am also changing to a 2015 engine harness and the 2015 coilpacks. Everything should be done in little over a week as long as I get the parts.

I have a delicious tune. I just want to make sure I am not overlooking anything as this vehicle is a race car.

Sounds like you'll be fine in the long run, double check for vac leaks and clean your MAF sensor and ensure it's seating properly.

Sent from my XT1650 using Tapatalk

[steve99]

Check the di compiter ix grounded with all mounting bolts in place

[MCTeeJ]

Just a heads up, I had this same issue and it was the injectors themselves going bad, not the seals. https://www.ft86club.com/forums/show...5&postcount=27 I did a small writeup on my issue if you'd like to read it. Is your car still hitting target AFR after the miss occurs?

Edit: If it occurs in random cylinders it's more likely coil pack or plugs

[sfruski]

DI computer is mounted tight, though I am going to be adding an extra grounding strap directly to it.

No lean condition is seen in logs. If it was consistently one cylinder I would think it is an injector, but you can see the miss in all the logs. Again, each miss is also small enough that no check engine light come up.

Last track day had a cylinder three missfires and I replaced all the plugs and the coiloack on cylinder 3.

3,500 or so miles on this motor. (Car sat in a shop for four years before I brought it back to life. Incomplete race car build.)