15 challenger procharged strange miss at 2500 rpm

[GPGTP]

I'm willing to pay money to help solve this issue. The car has a miss at 2500 rpm and only at 2500 rpm.


If i try to command an AF ratio anything short of drowning the engine in fuel it will miss at 2500 rpm. I tried backing the timing way down and it still does it. ONLY at 2500 rpm. You can see from the scan labeled "miss" the narrow bands show a quick drop in voltage along with a blip on the wideband, this is followed by a noticeable "jerk". If I command ~9.0:1 it doesn't do it but thats just ridiculous. Even at 10.0:1 and 8 degrees it does it. At 9.0:1 i have can normal timing and it doesn't do it. You can see on scan labeled "miss" at 2:37 on the scanner the AF ratio is at a respectable 11.6:1 with 7 degrees and it does it. Also at 1:44 on the scanner it does it as well with 11.0:1 and 7 degrees.

Now on scan labeled "rich", AF is well into the 9's and timing is still at 7 and it does not miss. I can even command 12-13 degrees and it will not miss as long as the fuel is rich. Doesn't make sense to me. I shouldn't have to dump fuel in order to make the miss go away, especially since just before and just after 2500 rpm it doesn't happen at respectable AF and timing settings. Makes me thing something mechanical is going on, but what?


Car has a P1 procharger and a mild comp blower cam.

miss.hpl rich.hpl

[MarkTucker]

I am on my phone, so not able to look at logs.

Did you do the camshaft install?

[GPGTP]

I am on my phone, so not able to look at logs.

Did you do the camshaft install?

Yes the cam is installed and no I haven't messed with the vvt tables yet. I did not do the cam install, was done by someone else

[Road]

I have had the same problem before. If you will notice it does it under light transient throttle changes. Slight blip of the throttle = lean. Not much in the software for transient fuel and I have asked but was told that all could find. It may not be transient fuel it could be poor injector data I don't know. But try raping your injector data and see if that helps.

[GPGTP]

I have had the same problem before. If you will notice it does it under light transient throttle changes. Slight blip of the throttle = lean. Not much in the software for transient fuel and I have asked but was told that all could find. It may not be transient fuel it could be poor injector data I don't know. But try raping your injector data and see if that helps.

I've tried that but it's not a transient issue as it happens even if i punch it off idle. It's not a tip in issue. Doesn't do it unless at wot. by the time it hits 2500 its well past transient. The fact that its 2500 every time tells me something else is at work.

[MarkTucker]

I was just asking if you personally did the installation of the camshaft. Wanting to see if it was done correctly or not.

If lifters were replaced? If a VVT Limiter was installed?

[GPGTP]

I was just asking if you personally did the installation of the camshaft. Wanting to see if it was done correctly or not.

If lifters were replaced? If a VVT Limiter was installed?

Yea I realized that but I was running out the door when I posted that.

I did not install the cam. Supposedly the vvt limiters were installed. I'm not sure on the lifters, would that be an issue?

What are you thinking?

[Road]

I've tried that but it's not a transient issue as it happens even if i punch it off idle. It's not a tip in issue. Doesn't do it unless at wot. by the time it hits 2500 its well past transient. The fact that its 2500 every time tells me something else is at work.

Didn't realize it was at wot when it was doing it. For some reason your wideband is not following your narrow bands. I see a lean tip in on narrow bands and its rich on your wideband. And adding fuel helps the problem? This screen shot shows it to be doing it before wot and before 2500 rpm.
Untitled.png

[MarkTucker]

Nevermind it's a manual car. Sorry, just now looked at the logs.

[MarkTucker]

How about spark plugs? Have they been changed? If so or not, were they gapped down?

[GPGTP]

Didn't realize it was at wot when it was doing it. For some reason your wideband is not following your narrow bands. I see a lean tip in on narrow bands and its rich on your wideband. And adding fuel helps the problem? This screen shot shows it to be doing it before wot and before 2500 rpm.
Untitled.png

I'm not sure why your concerned about tip in, there are no issues at tip in.

[GPGTP]

Yes the plugs were changed to tr6's but I'm not sure what the gap is at. I will check

[GPGTP]

has me stumped. I've only ever saw an rpm specific misfire one other time in my career. That was on a 4th gen F-body with bolt ons. Happened every time at 5800rpm. Same tune I've used in hundreds of F-bodys. Months after I tuned the car the miss just magically goes away.....I give up. lol.

[GPGTP]

Yes the plugs were changed to tr6's but I'm not sure what the gap is at. I will check

plugs are gapped at .30".

I'm considering having a stock file flashed by the dealer, since we can't do write entire, change the plugs. If that doesn't work I'll just give it back to the owner and claim defeat.

[HackAbuse]

Hello, just wanted to chime in. The issue is definitely still occurring even when you have it running stupid rich, as shown below:
ali_rich1.png
ali_rich2.png
ali_rich3.png

Just for giggles, try modifying your VE table, where I've traced a line and column, change the axis to 1.10 Pressure ratio and 2500rpm. Where the two meet, set the VE value to ~105. Leave every other value around it to what you'd expect - leaving just that one cell and see what it does
ali_VE.png

For example:

ve1.png


Whatever is going on, it's clear to me that the engine simply isnt getting enough fuel at that moment in time. Whether it's the engine flowing a freakishly large amount of air at just that moment (2500rpmx1.1 pres ratio) or the injector data is somehow off, something is definitely awry with fuel

[Road]

The one I had doing that was a 2014 with a fully built motor. It was a lean spike during transient low rpm changes. After reading this thread am rethinking what was done with the cams as that could cause issues too?

[GPGTP]

Hello, just wanted to chime in. The issue is definitely still occurring even when you have it running stupid rich, as shown below:
ali_rich1.png
ali_rich2.png
ali_rich3.png

Just for giggles, try modifying your VE table, where I've traced a line and column, change the axis to 1.10 Pressure ratio and 2500rpm. Where the two meet, set the VE value to ~105. Leave every other value around it to what you'd expect - leaving just that one cell and see what it does
ali_VE.png

For example:

ve1.png


Whatever is going on, it's clear to me that the engine simply isnt getting enough fuel at that moment in time. Whether it's the engine flowing a freakishly large amount of air at just that moment (2500rpmx1.1 pres ratio) or the injector data is somehow off, something is definitely awry with fuel

Yea I agree it's still missing its just not as bad. I've gone as far as drowning it in fuel at that point and it doesn't help. I'm convinced the ecu needs a write entire.

[06300CSRT8]

Did you post the tune?

[HackAbuse]

He didn't post the tune yet

It definitely isnt a transient issue, since it's occurring so consistently and not when throttle changes are occuring

Could it have something to do with the cam phasing?

[GPGTP]

He didn't post the tune yet

It definitely isnt a transient issue, since it's occurring so consistently and not when throttle changes are occuring

Could it have something to do with the cam phasing?

I agree. I tried retarding the cam and it only lost power. Didn't change anything.


I can post the tune if you want.