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2G WOT hesitation

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Gilly17

Probationary Member
8
0
Jul 14, 2021
Clarkston, Michigan
Hey I just picked up a 97 eagle talon tsi awd a few days back and I love the thing. Unfortunately I am having a little issue when I get to about 4-5k rpms it kinda pops or hesitates right when the boost starts to kick. I thought it might have been a boost leak but it does not seem like I am losing any power it just hesitates. It wants to go and it rips in first but the other gears it hesitates and doesn't feel like it's at its full potential. It's got a 6 bolt swap and it was also burning oil but when I pulled the valve cover plate off, there were puddles of oil around the spark plug wires but the plugs were pretty dry even though the o rings are completely shot. The previous owner also said someone he let borrow it put regular gas in it... not sure how many times. She for sure needs a good clean.

Just looking for tips or advice from someone that's experienced this too or just any advice is welcome
Cant wait to get her running good again

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Solution
There was a little bit of oil in the 3rd cylinder plug but I’m almost positive it came from my leaky oil cap. Got new spark plugs, bpr7es because the turbo can do at least 20psi and it looks like a mild build for now, new oil and filter, new k&n air filter, still looking for a new oil cap but I appreciate the advice!
First thing you do with any DSM with a mass airflow sensor (MAF) is do a real boost leak test. Cars with a MAF are very sensitive to air leaks in the piping and intake system. Second thing I'd do is tighten the valve cover a little to make sure oil isn't leaking past it. If that doesn't work then buy a new valve cover gasket set.
 
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Oil cap gasket is probably hardened, feel if it’s soft with your fingernail, it should squish a little bit, if it’s hard then it’s bad. There’s no oil inside the spark plug wells right? Boost leak test is always a good idea, I’d swap the plugs with new ngk bpr6es and add the line back on the injen intake to the valve cover, remove that breather. it’s circled in yellow here:

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There was a little bit of oil in the 3rd cylinder plug but I’m almost positive it came from my leaky oil cap. Got new spark plugs, bpr7es because the turbo can do at least 20psi and it looks like a mild build for now, new oil and filter, new k&n air filter, still looking for a new oil cap but I appreciate the advice!
 
Solution
Oil cap gasket is probably hardened, feel if it’s soft with your fingernail, it should squish a little bit, if it’s hard then it’s bad. There’s no oil inside the spark plug wells right? Boost leak test is always a good idea, I’d swap the plugs with new ngk bpr6es and add the line back on the injen intake to the valve cover, remove that breather. it’s circled in yellow here:

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I’m just curious because this is my first dsm but why remove the breather? Is it actually hindering instead of breathing LOL
 
I’m just curious because this is my first dsm but why remove the breather? Is it actually hindering instead of breathing LOL
The stock configuration has that breather tube going back into the intake pipe. So the air/gas that's escaping the engine through there is technically a leak because it's no longer being reintroduced into the intake system. I don't know how much this hurts the operation of the car but that's the theory.
 
The stock configuration has that breather tube going back into the intake pipe. So the air/gas that's escaping the engine through there is technically a leak because it's no longer being reintroduced into the intake system. I don't know how much this hurts the operation of the car but that's the theory.

The air passing through that nipple from the valve cover back into the intake pipe is not a leak. It’s not part of the air metering process. The hose attaching the two acts as a vacuum source to help evacuate excess crank case pressure/gases/oil vapor.
 
^This. It’s not metered air so I don’t think it’ll cause issues having a breather there. That’s how my 2g was set up with MAF. Never had an issue.
However; along these lines, make sure if there is a port on the low pressure intake piping (past red injen coupler, before compressor inlet) that it is capped if you are not going to route the PCV back into intake.

I personally would avoid routing PCV back into intake as it will only dirty up the intake path with vaporized oil and fuel. The proper way to re-organize the PCV system would be to install a properly vented and baffled catch-can, as that breather filter will eventually saturate with oil and begin adding to the mess in the engine bay.
 
@Gilly17 to address your original concern, the hesitation could be a number of things. I would start with the plugs and gapping them to the above mentioned specs and see if that solves the issue. If not, it could be a lean fueling issue that could be diagnosed by logging a lambda sensor reading, or it could be knock causing a breakdown in combustion, or it could be too high of air charge temp, or any combination of those and unknown variables.

Ultimately, I think this is emblematic of DSM tuning culture, where owners bolt on parts and hope for the best. To modify the powertrain with any level of confidence, you need to be able to measure and keep track of engine actuator and sensor readings and in order to be able to track issues down in a systematic way. This will require data logging software or the installation of a standalone EMS altogether.
 
Oil cap gasket is probably hardened, feel if it’s soft with your fingernail, it should squish a little bit, if it’s hard then it’s bad. There’s no oil inside the spark plug wells right? Boost leak test is always a good idea, I’d swap the plugs with new ngk bpr6es and add the line back on the injen intake to the valve cover, remove that breather. it’s circled in yellow here:

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What could I use to plug the hole just a screw or is there something else?
 
You're seeing fuel cut.

MAF is reading more airflow than it should with the stock ECU. 6-bolt swaps, and larger turbos on a 2G are notorious for this (as well as vacuum/boost leaks) when you don't either have ECMLink or wire in a fuel-cut defender, variable potentiometer, etc. Stock ECU mapping will pull fuel when it sees higher than expected airflow to prevent an over-boost situation.
 
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