FRPP Intake Manifold stumble? (To keep or not)

[702GT]

So I've reached out to the S197 community before about my issue with the FRPP intake manifold with no real responses, and from what I've searched no one else seems to have this issue with the manifold, so I thought I would bring it to tech before I make a deicision on keeping it on the car or going back to a stock manifold.

Current hardware for reference:
FRPP Intake Manifold
Comp Cams 127020 (Thumpr Stage 2 NSR) w/Comp Phaser Limiters
Pypes LT Headers & O/R X
JLT CAI

At about 1/2 throttle around 3,000rpm the engine stumbles and pops. I can baby the throttle past 3,000rpm and it will rev through clean. I can free rev the car at any throttle position and it won't stumble or pop. At WOT starting below 3,000rpm the engine still stumbles a bit and gets a little poppy going through that 3k/rpm range. So it only does it when the engine is under load in that rpm.

My tuner has tried everything he can think of, and even consulted other tuners on the matter and they've agreed with his methods and had no further input other than it's a hardware issue, such as the cams, and not a tune issue. The car isn't pulling timing when it stumbles, but we even tried running it on race gas just to be sure, and no effect.

BBR says it's the comp cams. But TBH the Thumpr's aren't a terrible grind, what most people don't care for is the LSA and weak lift. The duration is actually a nice profile at 234/[email protected]". I like the sound and wide power curve of the cam, but no it doesn't make the most peak power. If it is the cam causing this issue, then my question would be why? What is the thought behind it? Is it the issue because it's not an aggressive enough cam for the manifold? I had the cams in long before the FRPP intake and LT headers, and the car ran absolutely flawless and never had an issue at 3k/rpm, or any rpm for that matter. I find it hard to believe the cams are the issue, when I didn't have the issue until the FRPP went on. I'm not gonna dump $1,000 on a blind fix. Saying comp has shitty grinds isn't a good enough reason. Tell me the LSA is bad for an aftermarket intake, now we can go somewhere with it.

I'm scheduled at the dyno shop next wednesday, so I really hope I can get serious feedback on this. If not, I'll go with my gut and swap the manifolds.

 

[Johngt]

Have you checked with comp cams at all?

 

[gil_t2]

As easy it is to swap manifolds, I would put the stock back on and see if that stops the miss. If it does it is a bad manifold, if not then cams are bad.

 

[Johngt]

yeah that or maybe a bad tune

 

[TheKurgan]

Tune.

 

[Greg Hazlett]

+1 on the tune.

 

[GrnBullitt08]

Sounds like the tune. I would get an alternate email tune to justify that it's not the issue if not throw the stock manifold back on.

 

[BruceH]

I had that manifold with 127300 and 400 cams, never had an issue. There isn't anything special about tuning for it either so I doubt it's the tune.

Forgive me for asking but it has to be asked, did you use a torquing pattern when installing the manifold? Did you use a torque wrench? Have you gone over all the air intake and vacuum connections? I'm asking because it sure does sound like you are experiencing an air leak somewhere that only shows up during certain conditions.

 

[Greg Hazlett]

Bruce, I disagree with your saying it is not tune related; both Jeremy and I had the stumble with the FRPP intake that our tuner had to adjust something for...what it was I can't remember.

If he had a leak it should trip a CEL.

 

[702GT]

I'm fairly confident the cams are fine. Cams ran fine before the manifold. Greg do you have the number of your tuner so mine may talk with him? I would hate to spend money on an email tune just to prove if my tuner knows what he's doing or not. More so, buy a tune and it doesnt make a difference, then I'm out money anyway lol.

 

[one eyed willy]

was the intake new? i agree with puttig the stock manifold on and checking it with the stock manifold.....inspect the frpp and see if there are any issues....

ive had vac leaks before with no CEL's......are you datalogging at all? wideband? no changes were made when i put my c&l manifold on, no issues afterwards.

if the manifold is in good shape and nothing out of the ordinary, then i would look at the tune, but to me it sounds like something phisycal.

cleaned your maf latley? changed plugs?

 

[screamingstang]

Sounds like toy need an update tune from bbr..

 

[702GT]

was the intake new? i agree with puttig the stock manifold on and checking it with the stock manifold.....inspect the frpp and see if there are any issues....

ive had vac leaks before with no CEL's......are you datalogging at all? wideband? no changes were made when i put my c&l manifold on, no issues afterwards.

if the manifold is in good shape and nothing out of the ordinary, then i would look at the tune, but to me it sounds like something phisycal.

cleaned your maf latley? changed plugs?

I *can* datalog the car, problem is no one who knows what they're looking at is willing to look at it, without me buying their tune. I've checked for vac leaks, sprayed all over the manifold runners, injectors, CAI, got nothin. My A/F is spot on. Idles/cruise 14.7, WOT 12.8 N/A 12.0 Spray. The only changes that were made to the car was the FRPP and LT's at that point in the build, and it never had a stumble prior to the manifold. I bought the manifold brand new from Ford Racing. I did change out the spark plugs from HT1's to HT0's. Also bought new. When we realized I had the problem, I pulled all the HT0's and double checked for gap and damage, plugs were still clean and gapped to .040"

I've cleaned my air filter and MAF several times. I always clean my MAF and air filter before a dyno.

I was hoping more for someone to jump in and say "I had that issue as well, this was the cause/fix." I had my FRPP off the car last month when my alternator took a dump. Nothing looked out of place on the manifold, as far as cracks or anything. I'd think if it was cracked I'd have a vac leak. If I take the manifold off to test the theory that it's simply the manifold itself, and it is, it won't be going back on. Greg says he's had the issue, so I'm going to try and follow that lead. It'd be great if I could talk to his tuner, or if he could remember what the fix was.

Sounds like toy need an update tune from bbr..

My tuner is local, not BBR. As I said, I'll take the manifold off before I buy another tune that may end up being a waste of cash. If Greg has had this issue and his tuner knows what it is, that's the person I want to talk to, and if he wants money to devulge the solution, then so be it.

 

[702GT]

I had that manifold with 127300 and 400 cams, never had an issue. There isn't anything special about tuning for it either so I doubt it's the tune.

Forgive me for asking but it has to be asked, did you use a torquing pattern when installing the manifold? Did you use a torque wrench? Have you gone over all the air intake and vacuum connections? I'm asking because it sure does sound like you are experiencing an air leak somewhere that only shows up during certain conditions.

If I do have a vac leak, I've had it for a good year so far, and made a great many WOT N/A and spray pulls without inccident. A/F is always peg on, and I can monitor my spark timing via Livewire as well. I would think if I had a vac leak I'd have lean conditions, or at the very least lean during those certain conditions as you mentioned.

I followed the torque pattern that is shown in the instructions as well as torque specs. I also used a craftsman inch/lb torque wrench. I'm pretty anal about procedures and instructions. Asking if someone followed the instructions or not isn't a crime lol, I'd say the same thing.


Edit: Also, thanks for all the input so far guys! At least it looks more narrowed down to the tune. Where are you Greg!? lol

 

[one eyed willy]

so you also went from ht1 to ht0 at the same time as the manifold?

 

[rojizostang]

just curious...when you say the motor is poppy, is it popping back thru the intake, or thru the exhaust?

 

[UltraKla$$ic]

so you also went from ht1 to ht0 at the same time as the manifold?

This really stuck out to me as well.

If you've checked the manifold itself, and all connections for leaks that's one problem out of the way.

If you trust your tuner but you say this:

I *can* datalog the car, problem is no one who knows what they're looking at is willing to look at it, without me buying their tune.

I'm a bit concerned over your tuners capabilities if HE can't interpret datalog readings since you're running his tune.

Summary: if there's no air leaks, then tune or spark or both.

 

[Johngt]

You may see if bama at AM can help you.

 

[WarFords]

Just swap it. It will only take like an hour.

 

[BruceH]

If I do have a vac leak, I've had it for a good year so far, and made a great many WOT N/A and spray pulls without inccident. A/F is always peg on, and I can monitor my spark timing via Livewire as well. I would think if I had a vac leak I'd have lean conditions, or at the very least lean during those certain conditions as you mentioned.

I followed the torque pattern that is shown in the instructions as well as torque specs. I also used a craftsman inch/lb torque wrench. I'm pretty anal about procedures and instructions. Asking if someone followed the instructions or not isn't a crime lol, I'd say the same thing.


Edit: Also, thanks for all the input so far guys! At least it looks more narrowed down to the tune. Where are you Greg!? lol

I had to ask the obvious. I've had similar symptoms caused by small air leaks in the past. Things like a silicone hose slipped off a little but not enough to notice with a quick glance, left a pcv line off once, another time I had damaged a fuel injector oring during assembly. The result was tip in problems. At wot it would seal but anything less and there was a small air leak. Lived with that one for about two weeks until I decided to start disassembling and found the damaged oring.

Good luck with it.