Hey guys, so I've been having a misfire/backfire issue that came out of nowhere and is driving me nuts... First step I changed the plugs and gapped them to .025, with no change. From there myself and a buddy of mine did a compression test with values within ~5psi of each other (I forget the exact values) but looked good. After that we checked both cam sensors, the crank sensor, and TPS with an oscillometer and all showed nice square waves. We checked, and I'm getting a nice spark from the Spoolinup COP through the plugs. I checked timing, and all marks matched up on the cam gears and trigger plate with no play in the trigger plate. We checked the injectors, and cleaned them up with no change. I'm kind of at a loss where to look next, as I'm now starting to think it may just be in the tune? When the car is idling the AFR's are all over the place, and while running the car is pig rich. The misfire happens when free revving in neutral or in gear, but always happens between 3-4,000rpm's but clears up immediately after and pulls hard, just rich. Also, my car is on tuned on speed density. If anyone has any suggestions, it would be greatly appreciated as I'm about out of ideas. Perhaps I overlooked something, but at this point I'm just not sure where to look next. Thank you in advance!

 

Post logs so we can help diagnose.

 

Yeah work has me away from my car for the next few days but I will get some and post up.

 

Since the car is on speed density I would start by substituting the map sensor with a good known unit. Especially if its a Omni. Very common they go bad.

 

I did just replace that with a brand new Omni 4 bar, however, I suppose it isn't out of the realm of possibility that it already crapped out... Thanks for your input

 

Well, I was finally able to get a log after a couple "speed bumps", I'll call them, in my build. Anyways, here it is... I'm new to evoscan/ecuflash so bear with me as I'm a bit slow with computers and programs. If anyone sees anything that stands out as a potential cause please let me know

 

Your must add load1B and AFR from your wideband, O2FeedbackTrim, FuelTrimLow, FuelTrimMid and Boost from your Omni 4bar before we have enough information to help.

 

I had all of that stuff turned on I'm not sure why it's not displaying the values. My O2 won't be displayed as I have no exhaust on the car yet. I'm trying to get it diagnosed while I wait for Robispec to send my coilovers back which I need so I can bring the car to get the DP made.

 

Here's a quick video of the tach while I'm in neutral slowly revving into the misfire. You can see the needle drop when it starts to misfire then eventually clears up around ~4,000rpms give or take.

 

I agree to check your OMNI, those things are way to notorious for going out, even new

 

Yeah I'll do that next, thanks. That would be pretty upsetting if that's the case...

 

No exhaust?

 

At the moment, no, but it did this with exhaust. I'm just trying to diagnose while I wait on Robispec to get my suspension back and the car is on jackstands.

 

Tested the Omni this morning, and it's working as it should. Waiting to get my base map from Tom to see if that changes anything.

 

still no change...