'10 Speed3, +25 STFT at idle/rough

Hey guys, want to start of by saying thanks for any help.

I bought a Speed3 and it was having issues, previous owner was not maintaining the vehicle and was being rather rough with it. I got it home, fixed the obvious issues (overly worn pads/calipers/new oil pan) but had a persistent hiccup when getting into boost. Replaced spark plugs, properly gapped, and ended up ripping two ignition coils apart in the process. They had been removed before and no care was taken in retrieving the bottom portion. So bought new coils to replace the ones that were old (160k miles, assume they were stock) and took it out for a drive. Car ran great, got it up to temp, and on the way home got into boost to see if the issue had been resolved.

Felt great, until it didn't. Cars STFT shot up to +25 and became practically locked there. Outside of removing and reinstalling the TMIC, coils, and a recently cleaned MAF.. nothing had been messed with. There's no 'obvious' vac leak that I've found so far.

https://docs.google.com/spreadsheet...WoRNYzEtMBL2P3z92v5Ep3ckFb26oP0JWUy7q/pubhtml <-- Short log

 

Vac leak or bad o2 sensor, based on that +25 trim and lean afr. You can build a cheap smoke tester using a mason jar, soldering iron and baby oil. What does happen when you go wot?

 

During 4th/5th in boost is when the problem suddenly happened. I limped her home the remaining 1/4 mile or so. When I slammed on the gas AP claims 0 STFT/LTFT, but is was still stuttering a ton. Car barely wants to start, super choppy, 'smooths' out some after getting going. I haven't actually drove the car any more since the problem started and only started it a few times for short periods to see if I could locate a vac leak. With how choppy the idle is, I honestly couldn't tell, but there was certainly no discernable difference when dousing areas with brake cleaner, and I've stripped down all the easily accessible hoses to inspect for wear and tear. Are there certain areas I need to (re)visit, common failure points?

I will also mention that I seem to notice the turbo far more than previously. A small blip on the gas and you could -barely- hear the turbo winding down over the typical engine noise, but now it seems very pronounced. Being seemingly more audible from beginning to end.

I wouldn't imagine that the O2 going bad would of been so abrupt, more a slow decline into a failed sensor. I have ordered a new O2 and a new MAF just to throw parts at it, yay Amazons return policy =X

I grabbed some parts to do a boost leak test, but I need a slightly smaller band clamp than I have. As for the smoke test, where would I route this through?

 

Check the gap on your spark plugs

 

You have a massive vacuum leak somewhere after your MAF. Don't use brake cleaner, use soapy water and hose down your air pathway with a boost leak tester attached where your air filter would be. With 18+ afrs and +25 STFT, the leak should be very apparent once you start pressurizing the system. Might want to check that you have a gasket installed behind your intake manifold too since the previous owner sounds like a doofus.

 

Plugs are gapped to .028
Boost leak tested - Oil cap holds 0 pressure. Would be pretty odd for the cap to of suddenly started causing these issues. I noticed before hand, when changing the oil after getting home because everyone says 'recently changed oil' when selling their car, that the oil cap had two o-rings. Didn't pay it a bit of attention. After taking a second to look, obviously mismatched o-rings that 'maybe' worked at some point.. but I don't see it. So not convinced that is my (entire) problem but.. No other leaks found, expected minor bubbling at BOV.

I'll throw stuff back together tomorrow and just cover the oil filler hole to see if anything improves. Already ordered a cap because it certainly needs to be replaced regardless of if it corrects my problem or not. Though my fingers are certainly crossed.

Want to say thanks again for the advice guys.

*New oil cap immediately corrected STFT, haven't taken it for a drive yet, reset ECU to forget the trims it was trying to learn. Will post back after I tear it up again.

**Back to how she was before 'problems' began. Adjusted BOV as well since it was entirely to soft. Fairly sure the remainder of the issue I'm having is purely because it is an OTS tune-- getting into high/long boost and getting some sputtering.