Open loop may not be as rich as Power Enrichment. Can you post your bins again (also the ones you richened up)? I can calculate the commanded AFR for each condition and that could still tell us something. And if you have any datalogs corresponding to those.

Also want to see your Power Enrichment thresholds again. Heavy throttle in low gear (even though foot not to the floor) can be very high manifold pressure, potentially enough to trigger PE.

It could be that my theory is correct, just for different reasons.

 

I am attaching three bin files. The names are self-explanatory. Apparently I just tacked on the enrichment to the open loop bin, so I don't have a "rich closed loop" bin. For what it's worth. Also I ripped the PROM and found out that the car is currently running on the "rich open loop" bin. I could've sworn I had reverted it back to a previous, non-experimental bin, but I guess not. I used a binary comparison software to figure out which bin I ripped from the prom.
I added the third, the Stock VE bin, in case you want to see what the car SHOULD be running on. This is the bin I had intended to revert to after testing, but apparently forgot. It should have all the changes you recommended before, without any experiments.

Here is a google drive link. Enclosed is a log file for this bin: https://drive.google.com/drive/folde...Pf?usp=sharing
I can't upload .xdl files directly to the forum. The log titled "to harps" corresponds to the 5.7 Stock VE bin

 

Ok so I took a look at this stuff...

1.) In the open loop rich datalog, it's still getting into closed loop. Not sure what bin that corresponds too. But the O2 sensor appears to be bouncing between rich and lean seemingly normally... particularly in the 2000-4000 rpm range and 0 to 60 kPa MAP.

2.) As I suspected, the open loop commanded AFR's are quite a bit leaner than power enrich. If you did have a partially clogged injector(s), it could be that it needs the PE level of enrichment to command a sufficient pulse width on the injector(s) to deliver an adequate amount of fuel to over come it and avoid the misfire.

Commanded Open Loop AFR at 92C - Rich Open Loop bin



Commanded Open Loop AFR at 80C - Stock bin



Commanded AFR Power Enrich



3.) PE enable settings are at 70% TPS and 91 kPa, so it could be that you're entering PE at only 70% throttle. But before that added enrichment, the misfire is occuring.

You must be running a 6 speed manual, and therefore AXCN?

Wonder what would happen if you tried the automatic ANHT settings on this? Then set your Min MAP for Power Enrich to something like 50 kPa. If the misfire disappears at much lower engine load, it might really narrow it down to fueling (and likely something on the passenger side where the ECM can't see it).

 

Ok that is great so I would concentrate with misfire under load common causes, Number 1 is spark plugs, 2 ignition coil / module then 3 intermittent injector fault or ECM injector driver circuit? double check the grounds, confirm injector and ecm grounds are good. Also don't forget the ground wire to engine / chassis that flat braid can corrode... Yes its a pain to check simple things like grounds, however a lot of things can have a simple cause. Anyway under load the injector pulse width is longer more load, confirm injector resistance is good, both hot and cold. Usually a bad enough injector fault will blow a fuse, however it may just fail to deliver adequate fuel when the engine needs it most and cause a misfire. Will be tough to find when something is intermittent, You may want to confirm fuel pressure before looking further into injector issues apart from simple resistance check especially when engine has run a while and everything is hot, will be good to know all resistance is good on injectors to eliminate that.

I have had bad "NEW" spark plugs, so don't trust looks good.... would be good to replace with new they are cheap, Confirm TPS sensor is good and goes from 0.54 @0% throttle to 4.5 volts @ 100% no need to run engine just ignition on. However you would get error codes if out of spec...

Just some ideas, oh don't forget to try disconnecting the tach wire at distributor. In case a wiring or tach filter coil fault issue affects ignition voltage, yes may be clutching at straws there but worth a look easy to unplug the tach wire at distributor cap ...
Good luck keep at it, yes is a pain in the *** to look at so many potential issues. However simple things can be overlooked, you really need to be able to confirm what is good to eliminate them.
​​​​​​Sometimes worth walking away and coming back a few days later with a clear head and enthusiasm 👍You will find the problem eventually
​​​​​​

 

The other thing is in the datalog I looked at, the BLM fuel trims looked pretty good.

Have you ever swapped the injector banks from side to side so the ECM can see the other injectors (via the O2 sensor)?

This is actually a reason I have O2 sensor bungs on both sides. Typically the other side has my wide band O2 in it. But even without a WB, it provides diagnostic capability such that I could move the narrow band ECM sensor to the other side and see what's going on over there.

 

Do you have a old school timing light? Tons of great info in this thread for you, and likely the issue may be resolved on your own by running the correct Bin now, hopefully! I think in either case, verifying your timing advance once the fueling is known to be good, will help ensure everything is working together in good order. At ths point if it's not the tune or the injectors, you're back to ignition. 👍

 

Yes I am using AXCN. I changed these values as you told me, and have a couple things to say. First, it was difficult to tell if the misfire cleared earlier. It was also difficult to find the "breaking point" where the misfire would clear. It's pretty random, and although it always occurs under the same conditions, it doesn't occur every times those conditions are met. It also varies in severity, and usually cuts in and out.

Anyway I did notice that every time the misfire cleared the O2 began to cycle between rich and lean. It would always show lean while misfiring, and usually went rich as it cleared (although sometimes it cleared and remained lean). Also according to the log the bin I'm using IS forcing it to stay in open loop, even though the O2 is still cycling. Should the O2 be cycling in open loop?

I'll put the log file from this in the google drive linked previously.

Also: I have not thought to switch injectors to the other side. This is actually a pretty good idea. I do want to get some datalogs with the engine in closed loop first though so I can compare it properly. It would be nice if I had two O2's, may be something to add in the future.

 

Yes! I already verified it at 8 degrees before. And I verified that the mark on the balancer was accurate.

 

👍 Hope you can narrow it down and get it resolved!

 

I think im pretty much out of ideas at this point. If you can swap injector banks that'll probably be a fairly big data point.

 

Are you sure it's 8 degrees advanced and not 8 degrees retarded?

Don't mean to sound insulting or anything, but I've wondered that throughout the thread.

 

Personally I think this is fueling. If it was timing it wouldn't clear up at heavy throttle I wouldn't think....

 

Yes, I'll get this done. Although I probably won't be able to today.

 

No offense taken. I'm sure it's 8 before. There's a large "BEFORE" stamp above the numbers.

 

dumb question egr valve ok? acting like a vacuum leak

 

The egr is disabled. The valve is still there but it's sealed. I can't remember if I have checked for vacuum leaks though, so I'll smoke test it when I get the chance.

 

Vacuum leaks on MAP cars don't have the same detrimental effects as on MAF cars. MAP cars don't directly measure airflow coming into the engine. On MAF car extra air coming in after the sensor is air that the ECM hasn't accounted for. MAP cars only measure engine load through manifold pressure. Generally On a MAP car air is air, no matter where it's coming in from.

 

Sorry for the delay. This week has been busy for me. The smoke test found nothing, it's sealed in tight.

I got a log in closed loop, which I'll put in the drive. I wanted to get as much information as possible before switching injector banks so we have plenty to compare it to. Unfortunately I have not yet switched the injectors and gotten the log. It may be another couple days before I can finish it. In the mean time, if you're interested in the closed loop log, it's there, otherwise I'll have these injectors done soon and will post when I do.

https://drive.google.com/drive/folde...PAq38TguD09fPf

 

The BLMs seems to a little lean at times, but then recover.

I don't know... nothing obvious is jumping out at me.

Probably just need to swap injector sides and see what the fuel trims do. Hopefully a smoking gun shows up.

 

Hope everyone is having a great weekend! Something that has nagged at me thru this mystery and I don't believe we really touched on: what brand/ style of injectors did you source for replacements? Please forgive this question if the answer is more obvious to folks like ULTM8Z, who have studied your Bin files. I'm wondering if your new injectors are causing a slightly lean condition during transitional throttle, likely due to a more precise spray pattern compared to the originals, and maybe simply need a slight bump in psi to offset the change, IF it can't be resolved by tuning the enrichment. And IF swapping injector banks doesn't present a more obvious issue. I've been warned I may need to do something similar, when doing further upgrades on my LT4 after switching to Bosch III's (same on my obd1 jeep stroker) Just an idea 💡 cheers!