Off Idle Hesitation Stumble

[TX-Ripper]

Just so we’re on the same page, was the car hesitating back when you smoke tested?

(my understanding is that something has changed recently)

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[Torinate]

No it wasn’t. It was perfect when I did. The smoke test then. I did it after the blower was on as kind of a “check” to make sure install was fine and there were no vacuum leaks. Idle vacuum hasn’t changed whatsoever since then.

This issue is a BRAND new issue as of Friday / Saturday. It’s never done anything like this in the past.

I’m going to be tryialing the Soler Performance throttle body so thought I would go out and take some logs before changing to it so I would have something to compare to. As luck and karma would have it, first stop sign on the end of my street I went to accelerate out and car just coughed and stumbled and hesitated to pull away after stepping on the gas. Then just took off. Likely was only a second but when you step on the gas and expect the car to pull away as normal and it stumbles and coughs it’s frustrating. Since then it’s been doing the same thing.

Nothing changed since when it was fine and now. Gas from same spot. Almost overnight lol.

This is why I’m not sure what it could be. Hasn’t been raced or drive hard in the last while.

 

[TX-Ripper]

And if it was still acting normally there be no need to test anything else

 

[Torinate]

Exactly.

I’m trying to figure out what changed or what the issue is.

 

[TX-Ripper]

Now that we are on the same page.

A new problem would require a new test.

 

[Torinate]

Absolutely. Have to figure out what’s going on. Something is amiss. Was hoping the logs would show something definitive. Without that, and without codes, it’s pretty hard to make a definitive diagnosis of the problem. Don’t want to assume the worst when it is hopefully something a little less involved. The car has an off idle miss and stumble. It was not revved to the moon or had a full speed run done with high temps.

Just wish there was a code or a tell tale sign in the logs pointing to something definitive. I don’t want to throw parts it to “fix” it.

Could be supercharger bypass valve - maybe. Oxygen sensor, MAF sensor, bad injector, dirty injector, throttle body, purge valve. Any one of those things. Not throwing any codes - no misfire codes.

I get starting somewhere, just not sure where. Plugs checked fine. Clean and gapped perfect.

Maybe try a smoke test. I wish pulling the injectors was a little easier. By far the hardest part of the whole supercharger install.

If anyone sees anything else or has other ideas of where to start I’m all ears!!

 

[Torinate]

Here's a couple of the logs. First one shows the 3000-4000 AFR1 drop and the second shows when I pull away. I am hoping someone can give some insight on where to go from here on a possible specific cause. TX-Ripper provided great feedback so that appreciated. Maybe someone can spot something hidden in the logs. I've reached out to Lund but haven't heard back. Again, this is more about diagnosing the problem than adjusting the tune I think. I posted on a different forum as well. I figure the more smart guys that see the better.

Thanks again... I know it's a PITA to try to diagnose via internet forums on a modified car, but hopefully there's something that someone sees to point the finger at. I'm great at the basics and turning wrenches, but all the PIDs and data they show is for smarter people than me...

https://datazap.me/u/torinate99/log-1656946033?log=0&data=1-16-17

https://datazap.me/u/torinate99/log-1656945992?log=0&data=1

Thank you.

 

[sloride]

Thanks for that TX-Ripper. I didn't see that I guess. I don't even see where the hesitation occurs. I even blew up the logs huge and cut them to try to pinpoint the event. I'll have another look. Going from negative to positive or vice versa I presume. The one log is weird. for 2 milliseconds there is a spot that goes from .78 afr to 1.23 then back to .8 afr. Sort of coincides with the vct2_intake stopping and torque source dropping (below).

What is vct2-intake? Is there a reason that it just stops in a log? It went from -21.29 to completely gone. Variable cam timing I am assuming. tq_source_pid went from 7 to 0 at this same time. These events took place within 0.06 seconds. No idea what they are or if they're related.

Appreciate the time and advice. Any info on these PIDs?

here are the tourqe sources

 

[TX-Ripper]

This issue is not tune related his issue is hardware related.

torque sources won’t help diagnose.

 

[sloride]

This issue is not tune related his issue is hardware related.

torque sources won’t help diagnose.

sure I agree. Just had them in case anyone was wondering

 

[Torinate]

This issue is not tune related his issue is hardware related.

torque sources won’t help diagnose.

I agree. Hardware related... didn't know if there was any correlation from VCT dropping off the log.

So bit of an update. Completed a compression test and everything was between 180 and 196 after 4 revolutions. Any more revolutions it went up but I was fine with the consistency. No dead holes. I initially thought you were nuts... then started to worry... then got to work and found my old compression tester. Did not do a leak down test as I don't have the equipment for that. Found my tester tucked in one of my tool chests... right beside my timing light lol.

Smoke test is tomorrow. I want to hope there's nothing... but I really want to find something. I am hoping a vacuum leak of some sort somewhere...

If not and smoke test is good, then i'm kind of at a loss. I'm going to try to post a blown up video of the spike lean condition that has me stumped more than the off idle issue. I don't know if they're at all related.

 

[Torinate]

here are the tourqe sources

Thanks for the codes! I’ve seen other ones come up in logs but didn’t know what they meant.

 

[Torinate]

Does this show my age? View attachment 687041

 

[kevinvan6000]

If you need a leak down tester, borescope or an injector cleaner I have all those if you want to borrow any of them to help troubleshoot.

 

[Torinate]

Hey Kevin.

Thank bud!

It’s pissing me off lol.

Been smoke testing the last hour and a half. Nothing! Not a bloody wisp anywhere. I keep taking more stuff off and pushing on stuff to try to find something but nada.

Compression test was great. Didn’t do a leak down. Guess I could borrow yours but honestly, if compression is fine and not showing anything not sure if a leak down would shown different.

I may borrow the borescope to have a look at the cats maybe.

I’m stumped and think I stumped even the smart guys lol.

I may take you up on the scope. I was hoping to find something with the smoke test but i think I’m going to call it - no vacuum leaks.

What’s your injector cleaner? Does it hook up on the rails or pull the injectors to do it? They were the single hardest thing to do on the whole install...

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