Part throttle pop/stumble through intake

[getdowngranny]

Here are the symptoms:
If I give it throttle at an average speed for normal driving, I get a pop through the intake at the same spot in the throttle (about 10% throttle). If I floor it, all is good. I can replicate the pop and make it do it over and over while driving in the same spot on the throttle or I can work around it and make it not happen (speed up or slow down how much throttle I give it). I cannot replicate it in park.

Here is what I have eliminated:
It's not the tune. It did it with the 5.7 chip, 6.1 chip, and it currently does it with XFI. Same exact problem.
It is not the cam sensor or position. I have the cam sync dead set on 90.
It is not the TPS. I replaced it with a new OEM unit thinking it was a dead spot in the TPS and no joy... Same shit.
It is not the Ingintion module or coil pack. I tried 2 different sets of type 2 coils and modules and 1 set of stock OEM coil pack and module. Same symptoms on all
It is not the MAF as it currently does in on speed density and it did it before with the MAF.
Not injectors. Did it on 2 different sets
Not spark plugs or wires.

What am I missing to check? Could the IAC cause these symptoms? All numbers are good and within operating parameters on the scanmaster.

 

[juan89]

Cam timing or worn cam ?

 

[getdowngranny]

Cam timing or worn cam ?

Roller cam installed properly.

 

[No disintegrations]

I've found popping through the intake is almost without fail a lean condition. What else can make it lean besides what you mentioned? What things have remained the same through all of these setups?

 

[DeltaBravo]

vacuum leaks cause "leaning" at idle and part throttle...but under boost, it is just the opposite.

 

[getdowngranny]

vacuum leaks cause "leaning" at idle and part throttle...but under boost, it is just the opposite.

I haven’t chased a vacuum leak yet. I’ll have to do that next. But BLMs are good.


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[DeltaBravo]

I chase my vacuum leaks down with brake clean

 

[dank GN]

What does you have your cam sensor dead on 90 mean?

 

[dank GN]

That’s not how you set your sensor. The crank has to be 25* past TDC on the compression stoke then you drop the sensor in with the window of the sensor towards the drivers side then u bust out the volt meter and turn it CW then back CCW till voltage just drops then lock it down

 

[getdowngranny]

That’s not how you set your sensor. The crank has to be 25* past TDC on the compression stoke then you drop the sensor in with the window of the sensor towards the drivers side then u bust out the volt meter and turn it CW then back CCW till voltage just drops then lock it down

The cam sync at 90 is the Xfi flag. The crank is setup 25* ATDC. Everything cam/crank and sensor related has been set up properly and verified three times over.


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[getdowngranny]

What does you have your cam sensor dead on 90 mean?

XFI cam sync flag.


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[TurboBuRick]

Have you logged it? Post a file.

 

[getdowngranny]

Have you logged it? Post a file.

I’ll log it next time I take it for a spin.


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[DR BOOST]

isn't the cam sync on a xfi supposed to be 85? Also, does your cam sensor have excessive up and down play that would cause it to climb the cam gear during acceleration?

 

[BEATAV8]

On speed density.... you can try richening it up in the problem area. If you’re running near stoichiometric and having a pop or sputter then try richening it up a full point. 13.5 or so

I’ve seen FIC injectors pop like that too. I switched back to SMP

 

[GNRick]

Might as well replace crank sensor. Mine caused a miss at 35 mph but cleared up when I accelerated.

 

[Chuck Leeper]

A common thread?
Did you use the oem engine harness and the adapter, for the XFI?

 

[getdowngranny]

A common thread?
Did you use the oem engine harness and the adapter, for the XFI?

Yes but it was happening with the stock ECM and TT chip too.


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[Nick Micale]

I've found popping through the intake is almost without fail a lean condition. What else can make it lean besides what you mentioned? What things have remained the same through all of these setups?

All the effort chasing this issue has been directed on the electrical system and components, and nothing about fuel delivery?

I cannot see you have any data on air/fuel target, and actual a/f, or voltage or duty cycle which could indicate lack of fuel or bad gas.

One of the first items I would check is fuel pressure on a road test, but I would add 5-10 psi to base fuel pressure first.

I would also pull a couple spark plugs to check them as well.

 

[getdowngranny]

All the effort chasing this issue has been directed on the electrical system and components, and nothing about fuel delivery?

I cannot see you have any data on air/fuel target, and actual a/f, or voltage or duty cycle which could indicate lack of fuel or bad gas.

One of the first items I would check is fuel pressure on a road test, but I would add 5-10 psi to base fuel pressure first.

I would also pull a couple spark plugs to check them as well.

Welp. I bumped up the pressure to 43psi with the line ON and it seems to have fixed the issue.


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