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

[Mykol]

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.

Great point about the misfire code, I wasn't aware of this. The random misfire is very random when the CEL comes on, and the log sees that it's all the cylinders that are misfiring, so I don't believe it to be a spark issue.

Also, I'm very receptive to learning what is left to do with this tune. So far, I figure the Main VE table needs to be adjusted. I don't know what else to look at.

[Alvin]

Great point about the misfire code, I wasn't aware of this. The random misfire is very random when the CEL comes on, and the log sees that it's all the cylinders that are misfiring, so I don't believe it to be a spark issue.

Also, I'm very receptive to learning what is left to do with this tune. So far, I figure the Main VE table needs to be adjusted. I don't know what else to look at.

Yeah, the engine lope looks like a misfire to the ECM. It's watching for a steady cylinder to cylinder speed which is not what happens with cam lope. This is like tuning 101 info.. Pretty well known.

[Mykol]

Yeah, the engine lope looks like a misfire to the ECM. It's watching for a steady cylinder to cylinder speed which is not what happens with cam lope. This is like tuning 101 info.. Pretty well known.

Thanks Alvin, this is all 100% new to me. I've been doing my research on the youtubes, but I'm learning that there is a lot to learn

[Alvin]

Yes, there is a lot too this.. I was making that point though because your email tuner should already know this.. along with how important tuning the VE is on a setup like this.

[Mykol]

Yeah, I'm honestly a bit surprised at how much is lacking in the tune according to everyone else here. He's a well-known tuner.

[RDF1]

Yeah, I'm honestly a bit surprised at how much is lacking in the tune according to everyone else here. He's a well-known tuner.

You would be surprised at how many hack jobs are out there...

[bk2life]

You would be surprised at how many hack jobs are out there...

ive got one in the shop right now. Im honestly surprised 'he' let this go out of his shop.

[Alvin]

unfortunately all it takes to be a tuner on the internet is to copy the supported vehicles list from HPtuners website to your own Wix or godaddy website.

[edcmat-l1]

Yep there are far more unqualified than qualified. Even in higher educated occupations though there are/is a wide spectrum of abilities. There are doctors that suck at their job.

[2xLS1]

Yep there are far more unqualified than qualified. Even in higher educated occupations though there are/is a wide spectrum of abilities. There are doctors that suck at their job.

Just think for every class of Drs that graduate there is going to be one at the bottom of their class.

[edcmat-l1]

Just think for every class of Drs that graduate there is going to be one at the bottom of their class.

Yep. "What do they call the guy who graduates bottom of his class in med school? Doctor." LOL

[DodgeZ]

"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.

Isn't the crank relearn how the PCM learns where zero is? How to adjust for the differences in the crank, block, crank sensor from motor to motor. I am not sure how many degrees of play are in spec but the motor needs to learn where zero is, it bases the timing for fuel and spark assuming it knows where zero is. You don't like to adjust out the low rpm lope and keep the upper, say 1,200rpm up, misfires?

Great point about the misfire code, I wasn't aware of this. The random misfire is very random when the CEL comes on, and the log sees that it's all the cylinders that are misfiring, so I don't believe it to be a spark issue.

Also, I'm very receptive to learning what is left to do with this tune. So far, I figure the Main VE table needs to be adjusted. I don't know what else to look at.

Once you get it to run, you need to work on the idle, VE, MAF, and spark. I am assuming you bought HPTuners to do this. You can tune the idle and cruise with the narrowband o2s you have (assuming they are good) but you'll need a wideband to tune for WOT.

[edcmat-l1]

Isn't the crank relearn how the PCM learns where zero is? How to adjust for the differences in the crank, block, crank sensor from motor to motor. I am not sure how many degrees of play are in spec but the motor needs to learn where zero is, it bases the timing for fuel and spark assuming it knows where zero is. You don't like to adjust out the low rpm lope and keep the upper, say 1,200rpm up, misfires?

All the crank relearn is for is misfire detection. That's it. Nothing more complicated than that. If you have an aftermarket cam, with overlap, that lopes, your misfire detection is all but useless anyway.

Furthermore, if there isn't a crank/cam correlation code set, the PCM does not require a crank relearn procedure, period.

Don't over complicate it. Crank relearn has no impact on how the engine runs or how the PCM operates, other than misfire detection.

[DodgeZ]

All the crank relearn is for is misfire detection. That's it. Nothing more complicated than that. If you have an aftermarket cam, with overlap, that lopes, your misfire detection is all but useless anyway.

Furthermore, if there isn't a crank/cam correlation code set, the PCM does not require a crank relearn procedure, period.

Don't over complicate it. Crank relearn has no impact on how the engine runs or how the PCM operates, other than misfire detection.

I guess I don't understand this... Is it fake news?


"The following text is quoted from the 1999 GM F-Body Factory Service Manual:

Circuit Description

The Crankshaft Position (CKP) sensor sends pulses to the PCM as the reluctor wheel teeth rotate past the CKP sensor. The PCM uses the CKP pulses to synchronize the ignition and fuel injector operation, and to time the interval between each CKP pulse. The PCM determines when an excessive change in crankshaft speed occurs by comparing each new time interval with the previous interval. A misfire causes an unexpected change in the crankshaft speed. A certain amount of acceleration/deceleration is expected between each firing stroke, but if the crankshaft speed changes more then an expected amount, the PCM interprets this as a misfire. The interval between the CKP sensor pulses is extremely small. At high engine speeds, slight variations in the following components make misfire detection difficult: Crankshaft, Reluctor wheel, CKP sensor. The PCM learns variations during the Crankshaft Position System Variation Learning Procedure. The PCM compensates for these variations when performing detect misfire calculations. Only a scan tool can command the PCM to perform the Crankshaft Position Variation Learning Procedure again.


Perform the learning procedure after the following actions: A PCM replacement, Any operation or repair involving the crankshaft, the CKP sensor, or the CKP to reluctor wheel gap relationship, An engine replacement, The ignition switch is in the ON position until the battery is drained."

[2xLS1]

And all that goes out the window with a cam that has any lope. Misfire detection is looking for a smooth rotation of the crank reluctor. Do you have smooth rotation of the crank reluctor with a cam that lopes?

[SiriusC1024]

That service manual description is a simpler explanation of the simple explanation I already gave.

Understand that this cam itself will make the engine misfire at low rpm. Tuning can mitigate it, but it'll always be present. It'll clear up when the cam comes online. That's why the misfire detection tables are edited to max out the counter at low rpm. Keep the counters up higher around 2k rpm and up.

Unlike a factory cam, a cam with larger duration and tighter lsa will misfire by default. The tune has to account for this by ignoring certain areas. Otherwise, things like no TCC lockup happen.

Crank relearn should come after airflow tuning and AFTER a good baseline spark table is set.

[Mykol]

Once you get it to run, you need to work on the idle, VE, MAF, and spark. I am assuming you bought HPTuners to do this. You can tune the idle and cruise with the narrowband o2s you have (assuming they are good) but you'll need a wideband to tune for WOT.

Yes, I do have HPTuners. I can mess with what you're suggesting although I have little idea what I'm doing. I can do more research though. I tdid try the tune you posted and it didn't really help. My original tuner sent me a few updated tunes also and it did end up helping, but I still surge/stall when in gear. I talked to him on the phone today and after looking at the MAF frequency data, he suspects a vacuum leak. I'm going to look for that tomorrow.

[SiriusC1024]

Tell your tooner to get the VE table lined out.

[blindsquirrel]

Isn't the crank relearn how the PCM learns where zero is? How to adjust for the differences in the crank, block, crank sensor from motor to motor.

Find true #1 TDC with a piston stop, build a timing pointer and mark the balancer, set a fixed number for timing in either the tune or scanner controls, check the spark timing with a timing light before and after doing a CKP relearn. I'll wait.

[edcmat-l1]

I guess I don't understand this... Is it fake news?


"The following text is quoted from the 1999 GM F-Body Factory Service Manual:

Circuit Description

The Crankshaft Position (CKP) sensor sends pulses to the PCM as the reluctor wheel teeth rotate past the CKP sensor. The PCM uses the CKP pulses to synchronize the ignition and fuel injector operation, and to time the interval between each CKP pulse. The PCM determines when an excessive change in crankshaft speed occurs by comparing each new time interval with the previous interval. A misfire causes an unexpected change in the crankshaft speed. A certain amount of acceleration/deceleration is expected between each firing stroke, but if the crankshaft speed changes more then an expected amount, the PCM interprets this as a misfire. The interval between the CKP sensor pulses is extremely small. At high engine speeds, slight variations in the following components make misfire detection difficult: Crankshaft, Reluctor wheel, CKP sensor.

^^^ That's an explanation of how the system works NOT what the crank relearn does.

The PCM learns variations during the Crankshaft Position System Variation Learning Procedure. The PCM compensates for these variations when performing detect misfire calculations. Only a scan tool can command the PCM to perform the Crankshaft Position Variation Learning Procedure again.

This is the meat of it.

Crank relearn does nothing for timing, synchronization, engine performance, nothing.

OP needs to find a tooner who knows what they're doing.