Weird AFR/RPM issue and false knock with 2018 Intake Manifold. Help?

[Joe 5.0]

Last weekend, I had a professional shop install a 2018 GT intake manifold (non-ported), GT350 throttle body, and LU47 injectors on my 2015 Mustang GT. Since then, my idle and Air/Fuel Ratio have been weird.

The issues that I'm currently having:

1. My AFR fluctuates between 11.0 - 15.0, and it drops the lowest when coming to a stop, or lightly revving the RPM's at a standstill (please see video below). The car feels as if it's about to stall, then the AFR jumps right back up to around 13.8.



2. I have false knock when going WOT, and I'm really not sure what it could be (please see chart below).

3. I have hesitation on startup. Starting the car isn't smooth at all.

Does anyone have suggestions on what I should do? One member mentioned that he had similar issues because his mechanic forgot to re-attach/re-install the knock sensors, but I'm not sure if this applies to me because the car is reading knock.

Any help would be greatly appreciated. I'm frustrated. :doh:

Mod List:
2018 Mustang GT Intake Manifold (IMRC's locked out)
GT350 Throttle Body
LU47 Injectors
JLT Intake (intake tube touching inside of hood insulation; not sure if this matters)
Tune
Misc. suspension mods

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[kluke15]

gt350 tb? sounded like several tuners were having issues with it. maybe potential vaccum leak somewhere after the IM install? also say your jlt was touching the hood could be moving the maf maybe check to make sure that is clear of everything?

 

[Ace21]

I almost guarantee it is a tune issue. A lot of things need to be calibrated when changing TBs and IMs.

 

[Joe 5.0]

I almost guarantee it is a tune issue. A lot of things need to be calibrated when changing TBs and IMs.

I've sent 5 datalogs to my tuner and I'm still having the same issues. I'm planning on asking for a tune revision and re-installing my stock throttle body.

 

[Joe 5.0]

UPDATE:

I re-installed the stock throttle body and uploaded the tune revision and I got a "low oil pressure" light for the first time, so I didn't drive the car. I would assume that this a tune related issue. I'm waiting for a new revision from my tuner.

Here's some photos of how my vacuum lines are routed. One Mustang owner on FB told me that the purge solenoid hose (capped off on the left side hanging over the coolant tank) should be connected to Vac 1. He said this is probably causing me the trouble.

This is how the lines were installed. I've circled where the ports were capped off.

 

[Joe 5.0]

Help anyone?

 

[Kahboom]

Are you running lockouts or using the imrc? Hose does not need to be connected if running lockouts. As far as the knock it could be the GT350 TB as they rattle, the shaft and gears are loose, especially compared to the stock TB, for the tune Lund has noted to others that when you get a tune to let them know if you have a PP car, the person who did the revision might have missed it so you need another revision for the stock TB. I would check your exhaust for any bolts that are loose or anything touching and do another data log after the revision.

 

[Joe 5.0]

Are you running lockouts or using the imrc? Hose does not need to be connected if running lockouts. As far as the knock it could be the GT350 TB as they rattle, the shaft and gears are loose, especially compared to the stock TB, for the tune Lund has noted to others that when you get a tune to let them know if you have a PP car, the person who did the revision might have missed it so you need another revision for the stock TB. I would check your exhaust for any bolts that are loose or anything touching and do another data log after the revision.

I'm running the lockouts on this setup. So the solenoid and Vacuum 1 are OK to be capped off and not connected?

I also just received the revision for the stock throttle body and to account for the oil pressure light, so I'll be uploading that tune tonight.

 

[Kahboom]

Yes capped off just like a boss manifold or cobrajet when not using the imrc.

 

[Type550]

I had all sorts of annoying drivability issues with the GT350 TB coupled with my OEM GT IM (e.g. fluctuating idle, random stalling, surging at light/part throttle etc) which my tuner could not iron out, so as soon as we put the OEM GT TB back on, it's been running perfectly ever since.

I've read good things about the AED tune, so you might have better luck with them?

I'm thinking I'll revisit the GT350 TB + GT350/2018 IM in the future with an AED supplied tune.

 

[aleccesarenriquez]

I had all sorts of annoying drivability issues with the GT350 TB coupled with my OEM GT IM (e.g. fluctuating idle, random stalling, surging at light/part throttle etc) which my tuner could not iron out, so as soon as we put the OEM GT TB back on, it's been running perfectly ever since.

I've read good things about the AED tune, so you might have better luck with them?

I'm thinking I'll revisit the GT350 TB + GT350/2018 IM in the future with an AED supplied tune.

Your problems sound insanely similar to mine.

I get rpm surging at idle, which cycles between 500-1000 rpm until i apply throttle. My car stalls pretty often now; i.e. it often happens when I'm slowing down for a turn and I downshift to second and before I let the clutch out to start accelerating, it dies.

I have the 18 mani and gt350 airbox, so I'm not sure what's causing the issue. I'm starting to think it's the airbox because I have a stock throttle body, so maybe the adapter is causing problems. I did everything at once which was a huge mistake. Been thinking about trying a new CAI and seeing if the problems go away.

 

[Type550]

Your problems sound insanely similar to mine.

I get rpm surging at idle, which cycles between 500-1000 rpm until i apply throttle. My car stalls pretty often now; i.e. it often happens when I'm slowing down for a turn and I downshift to second and before I let the clutch out to start accelerating, it dies.

I have the 18 mani and gt350 airbox, so I'm not sure what's causing the issue. I'm starting to think it's the airbox because I have a stock throttle body, so maybe the adapter is causing problems. I did everything at once which was a huge mistake. Been thinking about trying a new CAI and seeing if the problems go away.

Yep, I had the stalling issues at low speed, usually when I was approaching a round-about traffic island... Car would stall going around it. Scary sh*t when there's cars behind you!!!

Once I went back to OEM GT TB it hasn't skipped a beat.

Your issues sound like a vacuum leak of some sort. Check all your vacuum connections I guess

 

[Joe 5.0]

Yep, I had the stalling issues at low speed, usually when I was approaching a round-about traffic island... Car would stall going around it. Scary sh*t when there's cars behind you!!!

Once I went back to OEM GT TB it hasn't skipped a beat.

Your issues sound like a vacuum leak of some sort. Check all your vacuum connections I guess

So your car runs perfect with the 18 mani and stock TB? My car doesn't stall, but I do get a drop at idle in the low RPM range when coming to a stop, or blipping the throttle at a standstill.

I'm stumped. :shrug:

 

[Type550]

No I'm running the OEM GT manifold with OEM throttle body now.

I'd like to try out the GT350 IM with OEM or GT350 throttle body and AED tune eventually, but am hesitant to lose some midrange torque.

Have you tried speaking with Shaun@AED ? He may have a tune for your setup, which might just need minor tweaks after a data logging session.

 

[aleccesarenriquez]

So your car runs perfect with the 18 mani and stock TB? My car doesn't stall, but I do get a drop at idle in the low RPM range when coming to a stop, or blipping the throttle at a standstill.

I'm stumped. :shrug:

My tuner is going to take a look at it again soon. As far as I know, they've done the exact same setup (18 mani, gt350 airbox with stock tb, ff tune, even down to the same exhaust - tsp headers + mbrp street catback) with another one of their customers. I spoke with the other customer and they said they used to run a pmas and since the switch to the gt350 airbox, their drivability got better :shrug:.

I spoke with my tuner today and he said they haven't had issues with the sleeve they use to fit the airbox to the tb, but he'll take a look at it anyways.

I'll let you know if messing with the airbox does anything, but if nothing is fixed, next best bet is the mani.

Also forgot to ask, are you on 93 or e85? Mine hesitates on startup as well but only when I'm running e85. Pretty sure it's normal, but I could be wrong.

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