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2G 97 Talon TSI AWD hard stuttering when getting into boost After 3" turboback installed..?

Classifiedcalli17

Probationary Member
8
8
Aug 1, 2022
Windham, Maine
Hey guys! First post on here, super excited to be a part of the community/website.

Okay, so recently i have come across my FIRST problem with my 1997 Talon TSI AWD 5-speed. I was looking/searching, and could not find an exact answer to my question. So let me explain what is going on. I bought the car BONE STOCK. Car only has 64k miles on it, and i am the 2nd owner. Ran/Drove perfectly UNTIL I recently had a full 3" turbo back exhaust installed.

Now a little back story. I have been driving the car on weekends, and nice weekdays that i get off. The upgrades i have done to the car are as follows.. Injen Intake, Greddy upper/lower hard pipe kit with fresh STM silicone couplers, Greddy type-s BOV (Recirculated) AND THATS IT. When the car had just those mods on it drove beautifully! didn't skip a beat at all.

I had swapped out the spark plugs to fresh NGK BPR6ES's gapped to 0.28 because it still had the OEM plugs in! I have not yet put on a new set of NGK 8100 plug wires.

The only code the car threw before exhaust was a P0141. (Rear O2 sensor) Like i said regardless the car drove fine. NOW i had a 3" Megan racing downpipe, and an HKS catback exhaust installed on the car. Nothing else has been touched, i have had the car in the air multiple times, checking everything underneath near the wastegate, all vac lines etc. I have looked everything over, and everything is the same way its always been.

Now when i take the car out, it runs/drives normal but the second i try to get into boost 50%-100% throttle the car falls on its face and stutters like crazy, creates zero boost, and feels like a nasty fuel cut, or boost cut. This car is still on the stock T25, and stock tune/boost, none of those lines have been changed.

I do not plan on modding the car further, I just wanted a nice intake, hard pipes, and a nice clean exhaust. Does anybody have any ideas on what could cause this?

I did read up people saying throwing a 3" DP on the stock T25 can cause "boost creep" due to the restricted factory O2 housing, but either way i feel i would still be able to get into boost? Any thoughts/ideas would be amazing, it's pretty frustrating, and would like to figure this out. Thanks guys!

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chrysler kid

15+ Year Contributor
2,520
524
Dec 20, 2002
Mckinney, Texas
beautiful car!

my fist suggestion would be to install a boost gauge. If you prefer to keep it stock looking you may just want to get a cheap mechanical one and pop it into the glove box just to keep an eye on

second thing to check is for boost leaks or vacuum leaks. Check the easy ones first, the vacuum connections on your aem intake that go to the vapor canister and to the valve cover.

also part if checking for vacuum leaks is replacing the pcv valve with a new one, they can get clogged and leak boost or vacuum back into the intake. You can clean them out with carb cleaner or brake cleaner, just make sure the little ball inside them rattles freely.

I never had boost creep issues on a t25, and to be honest the most boost a t25 will make isnt enough (in my experience) to trigger fuel cut. Thats what kinda of leads me to think you may have popped off a vacuum line or boost line in the engine bay
 

Vegas Smith

15+ Year Contributor
5,034
2,904
Dec 2, 2002
Houston, Texas
Car looks like shit. I'd maybe offer $1250 if you wanted to sell...If not, I suspect some type of boost creep if you're confident there aren't any vacuum leaks. Maybe the fuel pump is old and can't keep up now or injectors clogged and maxing out?
 

idkiliketurbos

10+ Year Contributor
784
128
Mar 2, 2009
Appleton, Wisconsin
One additional thing to check that could've gone bad is the spark plug wires. These will go bad and cause ignition studdering that can act like what you're describing. The timing seems convenient, but with a car this old, you never know.
 

CrackedDSM

10+ Year Contributor
2,155
811
Dec 17, 2009
Pensacola, Florida
Fuel cut is pretty cut and dry. You floor it, it makes boost, then suddenly you hit a wall. Like someone turned the engine off or you lost power. Boost falls, then climbs back up and bam. Hits a wall again.

If you floor it and it stutters/shakes/bogs, that sounds more like a misfire/ignition issue. It’s hard to describe a sound with words on the internet, so you might be describing fuel cut and I’m misunderstanding.

Do us a favor and record the car doing it. That’ll help diagnose it a little more. You can upload the video directly from your phone right here to tuners as well for ease of use.
 

Classifiedcalli17

Probationary Member
8
8
Aug 1, 2022
Windham, Maine
Update: So I filled a spray bottle with soapy water, and sprayed down everything under the hood while the car was running. No bubbles, everything is connected properly. I also checked the PCV valve for the heck of it, working as it should Ball moved freely inside (cleaned with brake clean, dried off and re-installed)

There is an exhaust leak in the center section of the exhaust (I had told the guys installing I wanted a fresh gasket/bolts in there) but obviously they ignored it.. also when I had the car up in the air, I went to check the rear o2 sensor and it literally fell out of the bung. (attaching a pic I found off google that looks identical to the rear o2 in my talon currently)

I will be installing new plug wires tomorrow, I ordered a set from Napa. Unfortunately no vendor around me stocks or can get the blue wire 8100 NGK plug wires so I'll at least start with these, and see if anything changes. I also have an appointment this Friday to a reputable shop I have used in the past to install brand new Denso front/rear o2 sensors on the car, and they are going to fix the leak in exhaust, survey the entire system, and fix any small leaks if present. Honestly, if the new plug wires, fixed exhaust/new o2 sensors don't fix the issue I am insanely stumped.

It's definitely not fuel cut. Once again car idles/runs/drives completely normal, but when you go to full throttle it, it stutters/bogs like crazy. It does sound like ignition misfire.

My next question is.. has anyone with similar simple boltons also with stock t25 run into this problem before? Can a leak in the exhaust, and a bad o2 sensor cause this symptom like a hard misfire? Thanks for the responses guys! I'll keep you all updated

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Classifiedcalli17

Probationary Member
8
8
Aug 1, 2022
Windham, Maine
*UPDATE*

I feel dumb. It turned out to only be plug wires haha.. they were original OEM wires. Swapped in some new wires and bam! the car RIPS now! smooth as butter. Thanks for all the help guys! I am in shock at how much a full 3" turbo back changes this car DRAMATICALLY! Especially on the tiny factory T25 turbo.. it's a completely different car! Very happy with it.
 

CrackedDSM

10+ Year Contributor
2,155
811
Dec 17, 2009
Pensacola, Florida
*UPDATE*

I feel dumb. It turned out to only be plug wires haha.. they were original OEM wires. Swapped in some new wires and bam! the car RIPS now! smooth as butter. Thanks for all the help guys! I am in shock at how much a full 3" turbo back changes this car DRAMATICALLY! Especially on the tiny factory T25 turbo.. it's a completely different car! Very happy with it.

Great to hear. I was thinking it had to be either wires or plugs that were gapped too wide on accident. Because that’s exactly what that sounded like. Previous posters hit the nail on the head. Glad it rips!

Post a sound clip. Freakin love the dsm 4G63t with a turbo back exhaust on it.
 

Classifiedcalli17

Probationary Member
8
8
Aug 1, 2022
Windham, Maine
One additional thing to check that could've gone bad is the spark plug wires. These will go bad and cause ignition studdering that can act like what you're describing. The timing seems convenient, but with a car this old, you never know.
Thank you very much! This did the trick, and she's running like a top now!

Great to hear. I was thinking it had to be either wires or plugs that were gapped too wide on accident. Because that’s exactly what that sounded like. Previous posters hit the nail on the head. Glad it rips!

Post a sound clip. Freakin love the dsm 4G63t with a turbo back exhaust on it.
Yes! thank you so much, The sound is so crazy when the wastegate flap opens up! Definitely have not experienced that before haha but it's sweet! I'll try to take a video at some point! I'm so used to my Srt-4 exhaust/sound and love that as well, but to hear it on a turbo DSM it's super awesome.
 

Classifiedcalli17

Probationary Member
8
8
Aug 1, 2022
Windham, Maine
That front oxygen sensor is still looking pretty sus, I'd replace it as well to be safe
I had both oxygen sensors replaced! Car runs like a champion! also.. no check engine light, and no codes when hooked up to a scanner.
I feel like having no check engine light in a DSM is actually pretty rare.. XD

New plugs.
New wires.
Both O2 sensors replaced.

Chipping away at it, and basically replacing anything that looks old/weathered.
My next little project will be replacing ALL of the vacuum lines with fresh hoses.
 

pauleyman

DSM Wiseman
8,297
2,843
Nov 19, 2011
oklahoma city, Oklahoma
I had both oxygen sensors replaced! Car runs like a champion! also.. no check engine light, and no codes when hooked up to a scanner.
I feel like having no check engine light in a DSM is actually pretty rare.. XD

New plugs.
New wires.
Both O2 sensors replaced.

Chipping away at it, and basically replacing anything that looks old/weathered.
My next little project will be replacing ALL of the vacuum lines with fresh hoses.
why would it be rare? I wouldn't have it any other way.
 

CrackedDSM

10+ Year Contributor
2,155
811
Dec 17, 2009
Pensacola, Florida
Just for how abused they typically are, and how many corners people cut on them? These have been, and are some of the most neglected cars on the planet. That's why to find a half way decent one is also rare these days. Just my opinion.

Just go read the comments on any YouTube channel involving a 7 bolt 4G63 and you’ll see just how true your statement is.

I wish I had a penny for every comment I’ve heard or seen over the years that mentioned “crankwalk” or “always has problems” when it’s 100% an ID-10T problem. I’d be a millionaire.

Was watching the cringefest that is Throttl’s YouTube channel involving their “more money than brains” 2G build and as soon as they got rod knock it was “herp derp dat 4G lifestyle. Lulz cranks walk” and it ended up being a spun rod bearing because they didn’t check tolerances properly and slapped it together. User error. But 99.9% of people in the past that do that just shrug and blame crankwalk and sell it.

/rant over. Basically f**k anyone who is stupid with these cars and can’t just take the L and realize it’s their fault.
 

pauleyman

DSM Wiseman
8,297
2,843
Nov 19, 2011
oklahoma city, Oklahoma
For some reason this is one of the only platforms I've seen that people just think things are easy. It isn't. The problem is the early mods are cheap and easy so owners think all of them are. It wasn't that way for the first 10 years.
 
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CrackedDSM

10+ Year Contributor
2,155
811
Dec 17, 2009
Pensacola, Florida
Yeah idk. These engines aren’t hard to me, but my god do regular mechanics who are great with Hondas, or big block v8s, champion winning people seem to struggle like crazy with the 4G63 and I’ve never been able to understand it. It’s like they refuse to research what these engines need and just do what works for x Honda or y SBF. Idk.
 

Classifiedcalli17

Probationary Member
8
8
Aug 1, 2022
Windham, Maine
Yeah idk. These engines aren’t hard to me, but my god do regular mechanics who are great with Hondas, or big block v8s, champion winning people seem to struggle like crazy with the 4G63 and I’ve never been able to understand it. It’s like they refuse to research what these engines need and just do what works for x Honda or y SBF. Idk.
I agree! It's HARD especially where I live up in the Northeast to find a qualified mechanic for this platform.. it doesn't make much sense to me. I will admit though when you pop the hood to a 4g63 DSM its MUCH more clustered than most.. it seems like they really over-engineered these cars for the time with tons of unnecessary stuff namely the five hundred vacuum hoses all over the throttle body/intake manifold, and all the electronics/smog/and being a MAF car. These cars can be irritating for the boost/vacuum leaks alone! They are finicky no doubt about it but isn't that part of their charm? XD
 
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