Off Idle Hesitation Stumble

[K4fxd]

@engineermike, What parameters would you like to see to try and figure this out?

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[engineermike]

@engineermike, What parameters would you like to see to try and figure this out?

Keeping in mind when trying to diagnose a momentary, specific issue the logging parameters should be a bare minimum and the fastest polling rate selected. It’s surprising how dense the data gets when you cut it down to 5 parameters or so.

If it’s an off-idle hesitation we’re seeing, I think I’d initially log rpm, pedal position, throttle position, spark timing, lambda, and injector pulsewidth. Once it’s narrowed down to air, spark, or fuel, you can cut out the unrelated parameters and add more to hone in further.

I just got done tuning out a tip-in hesitation on mine. I was initially able to narrow it down to air doing the above Then i killed the etc pid loop and logged maf, desired airmass, and vacuum, eventually tracing the error to the speed density model. Once it was fixed the tb model was wrong. Once I fixed that, the problem is gone. Just an example.

 

[Torinate]

Damn Todd, that sucks! I read through it and by page 2 I think my eyes were starting to glaze over. I hope you get her back in fighting form. These changes all took place after our trip to Mustang Day? She seemed to run fine then!

This is Dave lol. Stangtime is Todd. Too many aliases lol

It was doing this then as well that’s why I didn’t beat on it at all. Car runs fine really. Except the off idle hesitation and misfires lol.

 

[Torinate]

Keeping in mind when trying to diagnose a momentary, specific issue the logging parameters should be a bare minimum and the fastest polling rate selected. It’s surprising how dense the data gets when you cut it down to 5 parameters or so.

If it’s an off-idle hesitation we’re seeing, I think I’d initially log rpm, pedal position, throttle position, spark timing, lambda, and injector pulsewidth. Once it’s narrowed down to air, spark, or fuel, you can cut out the unrelated parameters and add more to hone in further.

I just got done tuning out a tip-in hesitation on mine. I was initially able to narrow it down to air doing the above Then i killed the etc pid loop and logged maf, desired airmass, and vacuum, eventually tracing the error to the speed density model. Once it was fixed the tb model was wrong. Once I fixed that, the problem is gone. Just an example.

Damn! Pretty in depth! I haven’t the skills or knowledge to do anything like that.
I can certainly log those things except pulse width unless VCM scanner can do that. Mine is a 2016 unless there’s a PID for that.
So likely not VCT then…

 

[K4fxd]

I don't think your tuner is going to ssend you log files with the parameters Mike suggests but it won't hurt to ask.

You will need at min a MPVI2 in order to use VCM scanner. If you have a SCT device you could log using that.

 

[Torinate]

Right now I have an nGauge. I can make my own PIDs to log outside of what the tuners log file is.

 

[MCS]

This is Dave lol. Stangtime is Todd. Too many aliases lol

And so it is!! Yeah, too many aliases. I need to figure out a way to paste names beside profiles.

It was doing this then as well that’s why I didn’t beat on it at all. Car runs fine really. Except the off idle hesitation and misfires lol.

Ahhh I just figured you were dropping the top to show us hard toppers what living is really like and also with the top down you weren't going mach 2 because the wind drowns out the music. Hopefully yours is a quick fix so next year we can run Ela against your drop top and see whats what

 

[K4fxd]

Right now I have an nGauge.

Ok, I thought you had the RTD.

If you can log the pid's above and I'll take a look. I'm not as knowlageable as Mike but I am willing to help if I can.

 

[Torinate]

Ok, I thought you had the RTD.

If you can log the pid's above and I'll take a look. I'm not as knowlageable as Mike but I am willing to help if I can.

Appreciate it.
Won’t happen until spring as the car is away for winter. I was hoping to replace / fix the issue prior to getting it out. At least do another compression test, pull the injectors and get them tested. Was hoping for an idea of what needs to be fixed so I could do it then. I’m not going through another summer babying the car because of an issue. The idle popping is annoying and when I let off the gas and slow down I get a small backfire. Really bugs my wife. But the worst is, stepping on the gas and expecting to move and nothing happens then it just takes off. Makes for a really jerky ride and takes the pleasure out of it.
Really, it’s either fuel, spark, air or timing of everything. Air looks fine. Fueling from what I see is fine - other than possible leaky injectors. Spark I’ve replaced plugs and moved coils with no luck. So what am I missing.
If I knew a new tune would fix it up, I’d jump at it. Just wish I knew more or knew someone close by to diagnose and fix it. All the shops I know of around here would just be taking shots in the dark as well. I’m even open to throwing some parts at it. But what parts is the question.

Sorry for the rant lol. First world problems…

 

[Torinate]

Ok, I thought you had the RTD.

If you can log the pid's above and I'll take a look. I'm not as knowlageable as Mike but I am willing to help if I can.

What’s the difference between the RTD and MPVI2? The VCM scanner is software correct? Those units allow the tune to be written and data logged if I’m correct. So which is better or offers more capability?

 

[K4fxd]

The MPVI2 or 3 is the thing to get. But really only useful if you want to tune yourself.

The Ngauge is fine unless you want to learn to tune.

 

[K4fxd]

The idle popping is annoying and when I let off the gas and slow down I get a small backfire.

Is it a backfire? or a pop through the exhaust?

 

[Torinate]

The MPVI2 or 3 is the thing to get. But really only useful if you want to tune yourself.

The Ngauge is fine unless you want to learn to tune.

Gotcha.
Yea, I’ve been reading up. I would love to tune myself. But don’t know enough.

 

[Torinate]

Is it a backfire? or a pop through the exhaust?

At idle the exhaust will pop and watching real time with Forscan that is the misfire. Here the pop misfire count goes up.
Come off the gas to slow down to stop and there is a louder pop from the exhaust. Sounds like a backfire, but not positive. Certainly a loud pop though. Only once though. I haven’t caught it on a log though and couldn’t watch the computer to see if it misfires then. Doesn’t happen every time, but enough to know there’s an issue.

 

[K4fxd]

What CAI are you running? and have you smoke tested it?

I don't see it in the logs but it sounds like a vacuum leak.

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