LQ4 to LQ9, with Truck Norris NSR: random misfire with rough idle and dies in gear

[Mykol]

I searched here for a similar issue but didn't find much. I'm looking to get a second opinion on the tune to rule it out as a potential cause.

Tune:
My 2003 1500HD LQ4 (with a 4L80E) was replaced with an LQ9 with a BTR Truck Norris NSR cam. I bought a tune via email however I get a PO300 random misfire code. The engine idles roughly in Park/Neutral (up and down) and wobbles the whole truck. When I put it in gear, the RPMs drop down to around 450 RPM then go back up but the truck struggles to keep idle up and it will die once I let up on the brakes. Bringing RPMs up to around 2k increases engine speed, but I don't feel like I have very much increase in HP/torque.

The random misfire affects all cylinders. Overall it just seems like the engine is starving for something.

Mechanical:
I'm in the process of eliminating mechanical causes:
Fuel pressure was tested with a mechanical gauge at 51 psi.
Spark plugs are new NGK TR6, gapped at .35" (although I noticed they looked dirty/fouled maybe).
Wires are red MSD 8.5mm.
Everything else is stock (exhaust, torque converter, etc.).
On a side note that I would be surprised if related: oil pressure is also low (30psi cold, 20psi warm).

Stock tune, purchased tune, and Log files are attached.

I appreciate any input. Thanks!

[DodgeZ]

See if this helps. Add all the idle stuff to your logs. STIT, LTIT, idle. Also add cylinder airmass.



LQ4-to-LQ9-with-BTR-TR-NSR-and-4L80E-TUNE-to-share - DodgeZ 20240930-01.hpt

[blindsquirrel]

If you're expecting it to have a smooth idle and lots of idle vacuum, you didn't do enough studyin' on what camshaft specs mean. That thing has a 107* lobe separation, it's supposed to idle bad. That's why that cam was invented.

[DodgeZ]

Also, with a new motor you need to do the crank relearn process. This is what misfires are calculated from.

[blindsquirrel]

Sort of... the crank relearn has to do with correctly identifying which cylinder is misfiring, not whether there are any misfires or not. Misfires at idle from a cam with built-in EGR isn't going to be changed by a crank relearn.

[Mykol]

Thanks DodgeZ, I'll give this one a go.

[Mykol]

blindsquirrel, I anticipated a "lob-lob" would be there, but not this extreme and not such a rough idle and ultimately dying when in gear.

[DodgeZ]

Sort of... the crank relearn has to do with correctly identifying which cylinder is misfiring, not whether there are any misfires or not. Misfires at idle from a cam with built-in EGR isn't going to be changed by a crank relearn.

The PCM learns the relationship between the crank and the sensor (when is running right). It can then judge a misfire because it knows what "good" is. The cam is going to cause issues with the misfires, as you know. He can adjust the misfires event time once it will idle. Or are you saying he shouldn't do a crank relearn after a motor swap?

[TheMechanic]

The PCM learns the relationship between the crank and the sensor (when is running right). It can then judge a misfire because it knows what "good" is. The cam is going to cause issues with the misfires, as you know. He can adjust the misfires event time once it will idle. Or are you saying he shouldn't do a crank relearn after a motor swap?

He is not saying NOT to do a crank relearn. He is saying that it needs tuning to stay running due to the valve overlap of this cam. That's not something that will be corrected by a CKP relearn. Likely if it is a fresh rebuild then he got something wrong. Maybe a vac leak at an intake seal, or a cracked plug during install, a switched injector plug or crossed HO2s sensors. Maybe just a little BRAF and compare to another vehicle.

[DodgeZ]

He is not saying NOT to do a crank relearn. He is saying that it needs tuning to stay running due to the valve overlap of this cam. That's not something that will be corrected by a CKP relearn. Likely if it is a fresh rebuild then he got something wrong. Maybe a vac leak at an intake seal, or a cracked plug during install, a switched injector plug or crossed HO2s sensors. Maybe just a little BRAF and compare to another vehicle.

I'd think the same thing. He always asks for the tune and logs but looking at the first tune posted. The idle airflow wasn't adjusted, overspeed/underspeed timing wasn't adjusted. I am assume he didn't look at the tune and just moved in to hyena mode about the cam he doesn't like. I'd ignore him but he replied to my comment amount needing to a crank relearn after motor swap. He could have provided feedback that cams are still going to cause false misfires. Which is true but a" crank learn" from a different motor isn't helping the problem, again hyena mode. Funny, I just saw a video yesterday about a stock motor with a lot of misfires and it needed a relearn.

[gtstorey]

I'd think the same thing. He always asks for the tune and logs but looking at the first tune posted. The idle airflow wasn't adjusted, overspeed/underspeed timing wasn't adjusted. I am assume he didn't look at the tune and just moved in to hyena mode about the cam he doesn't like. I'd ignore him but he replied to my comment amount needing to a crank relearn after motor swap. He could have provided feedback that cams are still going to cause false misfires. Which is true but a" crank learn" from a different motor isn't helping the problem, again hyena mode. Funny, I just saw a video yesterday about a stock motor with a lot of misfires and it needed a relearn.

You are really thin skinned if you think that is "hyena" mode. For around here that fuzzy puppy mode.

[blindsquirrel]

I'd think the same thing. He always asks for the tune and logs but looking at the first tune posted. The idle airflow wasn't adjusted, overspeed/underspeed timing wasn't adjusted. I am assume he didn't look at the tune and just moved in to hyena mode about the cam he doesn't like. I'd ignore him but he replied to my comment amount needing to a crank relearn after motor swap. He could have provided feedback that cams are still going to cause false misfires. Which is true but a" crank learn" from a different motor isn't helping the problem, again hyena mode. Funny, I just saw a video yesterday about a stock motor with a lot of misfires and it needed a relearn.

And I just saw a video about how Gamestop is going to infinity dollars any day now. What's your point?

CKP variation not learned cannot cause misfires. It can only mess up cylinder discrimination when a real misfire is occurring, or make it detect misfires when there aren't any. If there are real misfires like from a rumpity rump fake race car cam, CKP relearn isn't going to fix that.

Hey bud, click this link, it will not make me even a little upset: https://forum.hptuners.com/profile.p...ignore&u=44277

[DodgeZ]

You are really thin skinned if you think that is "hyena" mode. For around here that fuzzy puppy mode.

Maybe, he just seems to be a troll. Always insults people. Like if he isn't going to help why is he even replying? Scroll up, zero help in his replies. He knows the answers but chooses violence. Maybe his dad beat him for crying as a little boy, maybe he is ADHD and needs a little dopamine hit from picking on folks online, maybe he got bad grades in school and needs to feel superior to others by showing how dumb they are compared to him... I am not a doctor, but I do know it is pretty standard how he acts. Classic troller, again he knows stuff and can be helpful but most of the time it is troll mode.

I do find it ironic that he is one of the first people that points out that you need to post a tune file and a log for help.... This guy does it and he didn't even look at it. That made me laugh. Like F your "rumpity rump fake race car cam", that is how it is suppose to run.... LOL

[gtstorey]

Maybe, he just seems to be a troll. Always insults people. Like if he isn't going to help why is he even replying? Scroll up, zero help in his replies. He knows the answers but chooses violence. Maybe his dad beat him for crying as a little boy, maybe he is ADHD and needs a little dopamine hit from picking on folks online, maybe he got bad grades in school and needs to feel superior to others by showing how dumb they are compared to him... I am not a doctor, but I do know it is pretty standard how he acts. Classic troller, again he knows stuff and can be helpful but most of the time it is troll mode.

I do find it ironic that he is one of the first people that points out that you need to post a tune file and a log for help.... This guy does it and he didn't even look at it. That made me laugh. Like F your "rumpity rump fake race car cam", that is how it is suppose to run.... LOL

Can I just say you don’t know what the HELL you are talking about. He spends a lot of time helping, just maybe more blunt than some people like. I happen to like blunt.

[SiriusC1024]

Crank variation learn is autocalibration. The sensor picks up the leading and falling edge of the reluctor wheel. It's precise. Removing and reinstalling the same sensor is enough to throw it off. That's why a crank relearn should be done with a new sensor or crankshaft. The stored information is why relearn is done when an ECU or engine is swapped.

The reason for high rpm as part of the relearn process is to account for crankshaft flex and harmonics. On LS's the reluctor is on the end of the crankshaft. Hemi's have the reluctor in the center of the crankshaft to minimize error of piston position along the crankshaft.

When misfire occurs there is torsional vibration in the crankshaft and slight rpm change. This is detected on the leading edges.

Crank relearn will increase accuracy of misfire detection since it's the leading edges that are the concern.

OP needs to do a full tune. This cookie cutter purchased tune bs has left a lot of important stuff, such as VE, untouched.

[blindsquirrel]

I do find it ironic that he is one of the first people that points out that you need to post a tune file and a log for help.... This guy does it and he didn't even look at it.

It's literally in the fucking instructions at the top of the forum that nobody bothers to read. If someone posts asking for help and they haven't even put in enough effort to read the fucking instructions then yes, they deserve to be poked a little. Even if the question doesn't require those files to get an answer, posting them anyway shows that the person is capable of following instructions and so might be willing to accept the advice given. All too often the ones who don't post the files are the ones who already know everything and fuel pressure is fine actually 35psi should be good enough the pump is BRAND NEW let's move on just tell me what to change in the tune file to make car run good kthxbye.

It's clear you learned everything you know from yootoob videos and haven't spent any real amount of time in a shop, dealing with real issues, and fixing real cars, and knowing that to do that you need a plan, and the ability to follow logical clues, and the only way to get those clues is from DATA. Not keyword searches looking for the magic bullet, or vibes, or 'my buddy had one that did that kinda but not really maybe try checking the fuses' bullshit you seem so quick to offer up on here. And no, even this is not full hyena mode yet.

[DodgeZ]

Crank variation learn is autocalibration. The sensor picks up the leading and falling edge of the reluctor wheel. It's precise. Removing and reinstalling the same sensor is enough to throw it off. That's why a crank relearn should be done with a new sensor or crankshaft. The stored information is why relearn is done when an ECU or engine is swapped.

The reason for high rpm as part of the relearn process is to account for crankshaft flex and harmonics. On LS's the reluctor is on the end of the crankshaft. Hemi's have the reluctor in the center of the crankshaft to minimize error of piston position along the crankshaft.

When misfire occurs there is torsional vibration in the crankshaft and slight rpm change. This is detected on the leading edges.

Crank relearn will increase accuracy of misfire detection since it's the leading edges that are the concern.

OP needs to do a full tune. This cookie cutter purchased tune bs has left a lot of important stuff, such as VE, untouched.

Great info, thanks for taking the time to share it.

[Mykol]

Crank variation learn is autocalibration. The sensor picks up the leading and falling edge of the reluctor wheel. It's precise. Removing and reinstalling the same sensor is enough to throw it off. That's why a crank relearn should be done with a new sensor or crankshaft. The stored information is why relearn is done when an ECU or engine is swapped.

The reason for high rpm as part of the relearn process is to account for crankshaft flex and harmonics. On LS's the reluctor is on the end of the crankshaft. Hemi's have the reluctor in the center of the crankshaft to minimize error of piston position along the crankshaft.

When misfire occurs there is torsional vibration in the crankshaft and slight rpm change. This is detected on the leading edges.

Crank relearn will increase accuracy of misfire detection since it's the leading edges that are the concern.

OP needs to do a full tune. This cookie cutter purchased tune bs has left a lot of important stuff, such as VE, untouched.

I was wondering about VE, thanks for mentioning it.

[Alvin]

There is a lot left to work on in that tune.

*** Has it been mentioned that misfire diagnostics/codes will not work with a cam like this.. It will see the cam lope as a misfire. Does it have an actual misfire or is the diag by the misfire counters/codes etc.

[edcmat-l1]

"Crank relearn" is useless with any cam that lopes. Even if it sets the code (indicating a crank relearn is needed) just shut the code off.