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HELP cold starts like a champ. Dies when it comes up to temp


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I really want it to be a vac leak but I can't find one. 2005 LGT 5mt

Bnr16g, wahlbro fp, all catless, k&n intake, tuned. Happened out of the blue yesterday. Cold starts fine until I touch the gas pedal. Coughs sputters and dies. I did some heavy boosting after a car wash the day before? Water? Feels terminal. No smoke.

 

I pulled the TMIC and found no cracks, thoroughly checked as many vac lines and connections as I could and found nothing. Is throwing a CEL but I don't have a gadget to check it with. I'm afraid to drive it to local parts store to check code as it is difficult to keep running.

 

Still running the stock bpv TMIC and exhaust with the resonator box. I have not checked the maf yet because it is not just running poorly. It is barely running at all.

 

TGV? Dammit I need a gadget to pull the code

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Get your code scanned and probably will get the answer you are after. Is it possible it is a throttle position sensor? Temp sensor? MAF sensor? Crankshaft sensor? See my point. Your car is telling you what is wrong already with the code just need to scan it. $100 can get you a basic reader at the part stores now days and will save you much time having one now and in the future.
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my guess would be tgv as well, although it's not throwing codes about that, or about throttle-related stuff.
BtSsm - Android app/Bluetooth adapter. LV, logging, gauges and more. For 05-14 Legacy (GT, 2.5, 3.0, 3.6), 02-14 WRX, 04-14 STi, 04-14 FXT, 05-09 OBXT
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Tuner swears it has to be vac leak. My shitty little air pump only got up to 8lbs. I found a tiny leak but nothing like a hose off or anything.

 

When you did that pressure test, did it include the turbo inlet hose? Sometime those can disintegrate where it clamps onto the turbo.

 

If it's not that, then maybe as a test, try disconnecting the MAF connector and see if it'll start and let you rev it beyond idle. I would not drive it this way though.

BtSsm - Android app/Bluetooth adapter. LV, logging, gauges and more. For 05-14 Legacy (GT, 2.5, 3.0, 3.6), 02-14 WRX, 04-14 STi, 04-14 FXT, 05-09 OBXT
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Get your code scanned and probably will get the answer you are after. Is it possible it is a throttle position sensor? Temp sensor? MAF sensor? Crankshaft sensor? See my point. Your car is telling you what is wrong already with the code just need to scan it. $100 can get you a basic reader at the part stores now days and will save you much time having one now and in the future.

As an FYI several auto parts stores (AutoZone and O'Reilly Auto Parts are two that come to mind) will loan you a code reader. Go in and ask for one. They'll have you pay for it and when you bring it back they'll refund your money. There is a time limit that you'll need to return it otherwise it's yours.

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It happened the next day. I actually bought a brand new oem maf sensor. No dice. When I did the pressure test it included the turbo inlet.

 

Codes are maf low output and lean bank one. Takes quite a bit of stalling and rough running to even trigger cel

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  • 2 weeks later...

Have you every replaced the front O2 sensor ?

 

Thinking out loud here, if that's not reading right, it will send the wrong signal to the ECU to meter fuel on the wrong direction, either lean or rich ???

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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  • 3 weeks later...

Car is finally fixed. Mechanic tapped out quickly. Talked my tuner into fixing it as I had no other options. Codes had nothing to do with the actual failure. Codes stemmed from a grounding strapp that broke during the rough idle sessions while trying to keep the engine running. Cleared the codes and the problem remained.

 

The problem was in the fuel pump mods. There was too much play in the pinch point where the pump rests. One of the o rings was torn from movement I guess? It sealed enough to prime and start the car, but would not hold fuel pressure. I do not have anything in my garage to test fuel pressure. I just watched it prime fuel into a bucket and called it functional.

Miraculously I had just robbed a fuel sending unit from an 05 non turbo two weeks ago. My tuner (and now on call mechanic) was able to transfer parts from my sending unit (cap is different) and re-do the fuel pump mod properly.

 

Lesson learned : buy the Cobb upgraded sending unit, don't try to do the fuel pump mod on your sending unit unless you are really good with a dremmel

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