Fuel learn question

[relative4]

'05 LGT, Cobb stage 2. Just went through a long boost leak test process and replaced the TMIC, turbo inlet, bypass valve, and a few other vacuum hoses. None of these except the TMIC were really bad, but they were questionable enough to justify replacing while I was in there. The reason I went through this process was a whistle under boost. Pretty sure that was the BPV. Whistle gone now, and no boost leaks.

Having gone through all this, I decided it was time to familiarize myself with BtSsm. The LV from the first test drive after all this work is below. Basically, my fuel learn is 14-15% at idle and 7% while driving fast-ish. Am I looking at a vacuum leak? Any logging I should do to investigate further, or should I start with some spray testing?

Thanks!

[xt2005bonbon]

Yes. You are most likely looking at a vacuum leak. Positive values indicate just that. Negative would be boost leak.

 

btw, are you fully stock?

[xt2005bonbon]

Just saw your description says stage 2. Who tuned your car? Do you have an aftermarket air intake, and was your car tuned for it?

[relative4]

Only powertrain mods are catless UP (resistor mod) & catted 3" DP. Stock (bulletproofed) TMIC, stock airbox. Turbo feed banjo filter out, of course.

 

Today I spray tested the living shiznit out of it. At idle, the STFT is 3-4%. I used brake cleaner for the test, and if I sprayed a tiny bit of it right into the intake, the STFT immediately dove into the negative. I sprayed, nay doused, every single inch of the intake/vacuum/boost airflow sections. MAF O-ring, both ends of the hose from the airbox to the inlet, every port on the inlet, the inlet-turbo connection, every vacuum hose in the two tangles on the front of the manifold, the PCV tee and every breather hose on the back of the manifold. All the manifold gaskets, the turbo-TMIC gasket and BPV gasket, both ends of the TMIC-TB hose, the TB-manifold gasket. The brake booster hose and all sides of the booster (I have tested the booster to make sure it holds air after shutdown). The wastegate hose, the bypass hose, and more I haven't thought of here. Absolutely nothing downstream of the filter had any effect on the STFT.

 

Any thoughts on what I could be missing here?

 

Re who tuned it, I'm still on the Cobb map. Cryo is local and calling him has been on my to-do list since I bought this car a year ago, but I don't want to get on that dyno till I'm 100% sure everything is completely exactly perfect. I think this anomaly is the only thing left between me and full readiness.

 

Edit: when I was going through the boost leak test process, I disconnected the PCV valve from the intake manifold and tested it orally. Function seemed normal; allowed flow in only the appropriate direction. I suppose if the valve action is too light, it would be open too often. Does anyone have a substantive test procedure to determine whether the PCV valve is operating in spec? Thanks!

[pseank]

Get Dave involved now. Running off the shelf maps sounds dangerous to me. Dave sent me a break in map and then a base map. Over the 10 logs it took to get it right he helped me identify issues (vacuum leaks) 35,000 hard miles later it's still a beast. All this was via email. Email him and give him all your info and ask if he can help via email to get ready for dyno. Cryotune is a great choice or at least it was for me!

 

Sent from my XT1254 using Tapatalk

[Volta55]

Im in the same boat @OP... got my buddies smoke tester from work and tried the brake booster line and BPV line

http://i.share.pho.to/bef85a24_o.jpeg

(not my photo)

 

no smoke anywhere!

at idle, my learn is stuck at 14.99 but once i put my foot on the accel pedal, it goes down to almost 0

 

I want to fix this before my tune, but maybe the tune itself will kill this problem? i dunno

[relative4]

Made significant progress today, and it was so lame I'm almost too embarrassed to admit it here but I hope it will help someone. I had an STP "Premium" air filter. Swapped that out for OEM, and LTFT @ idle dropped to 7%. Not there yet, I want to get it to 0% if possible, and testing the PCV is my next step.

 

Haven't yet had a chance to get on the highway and do a real pull, so the correction charts haven't finished updating yet. Will post a new LV once that's done.

 

Also, the 7% LTFT is only with the A/C off. As soon as the compressor kicks on, the LTFT jumps up to 10-11%. Is this normal?

[xt2005bonbon]

I recall when the ac is on, it does affect a bit the fuel trims.

 

You have an off the shelf tune right? if so, then if you know for sure that you don't have any vacuum/boost leaks, then it is time to contact cryo to get a proper tune.

 

You see, amazing what a change of air filter can do huh.

[solidxsnake]

Your LTFT shouldn't be changing "as soon" as the compressor kicks in. It should take at least a minute or two (when idling), or much longer (if you're actually driving in the B-D ranges).

 

Also, it'll never be at 0%. Don't worry about them too much. If they're all reasonable (less than 10% or so) and somewhat stable (they don't change after a couple days of driving), then I'd just take the car in to get tuned. Dave will likely easily be able to tell you if there's anything else amiss while tuning it. The catback and the intake will both affect your tune, so there's no sense in chasing your tail if you don't actually have any leaks. Smoke test is your best bet to check for that.

[xt2005bonbon]

^ My fuel trims are within +/- 1%

[Phate]

If you have an accessport, monitor AF correction % and AF ratio, take it off your mount, and put it somewhere you'll be able to read it from the engine bay.

 

Now take a propane torch and a few feet of heater hose that fits snugly on the end of the torch, and make your tester. You can put a hose barb on the end to give yourself a smaller nozzle if you feel like it.

 

Start the engine, let it warm up to a stable idle, and turn off the climate control. Turn on the propane but don't light it, and start poking around the intake tract.

 

To see what you're looking for, put the propane hose in/near the intake snorkel. You should see the engine go pretty rich within a few seconds, and your AF correction will start pulling a ton of fuel because you are effectively enriching the fuel mixture with propane.

 

Continue poking around the intake tract, anywhere between the MAF and the cylinder head, holding it for a few seconds (you should see a reaction within 5 seconds) in place to see if the ECU reacts to anything. If the car doesn't react, there's probably not a vacuum leak there. Places to check: Around the MAF itself (bad gasket/o-ring under the MAF), after-maf hose, turbo inlet (check next to any of the barb fittings along the way, as well as where the turbo inlet meets the turbo), turbo to intercooler connection, intercooler seams, around the blowoff valve, and finally above/below the TGV's on each runner.

[relative4]

If you have an accessport, monitor AF correction % and AF ratio, take it off your mount, and put it somewhere you'll be able to read it from the engine bay.

 

Now take a propane torch and a few feet of heater hose that fits snugly on the end of the torch, and make your tester. You can put a hose barb on the end to give yourself a smaller nozzle if you feel like it.

 

Start the engine, let it warm up to a stable idle, and turn off the climate control. Turn on the propane but don't light it, and start poking around the intake tract.

 

To see what you're looking for, put the propane hose in/near the intake snorkel. You should see the engine go pretty rich within a few seconds, and your AF correction will start pulling a ton of fuel because you are effectively enriching the fuel mixture with propane.

 

Continue poking around the intake tract, anywhere between the MAF and the cylinder head, holding it for a few seconds (you should see a reaction within 5 seconds) in place to see if the ECU reacts to anything. If the car doesn't react, there's probably not a vacuum leak there. Places to check: Around the MAF itself (bad gasket/o-ring under the MAF), after-maf hose, turbo inlet (check next to any of the barb fittings along the way, as well as where the turbo inlet meets the turbo), turbo to intercooler connection, intercooler seams, around the blowoff valve, and finally above/below the TGV's on each runner.

 

See post #4 above.

[Phate]

See post #4 above.

 

Propane works way better than hosing the engine bay down with brake parts cleaner. It's an actual gas that will get sucked in anywhere there's a leak, rather than a liquid that you have to hit the right spot with.

[fahr_side]

Propane works way better than hosing the engine bay down with brake parts cleaner. It's an actual gas that will get sucked in anywhere there's a leak, rather than a liquid that you have to hit the right spot with.

 

 

 

And a smoke test is way faster for identifying leaks vs. watching AFR.

[Volta55]

So I bought a new OEM air panel filter, And my Fuel Learn at idle is down to 9 ( instead of

previous 14.99 ) but once i touch the accel pedal, it sticks to 0!

[solidxsnake]

So I bought a new OEM air panel filter, And my Fuel Learn at idle is down to 9 ( instead of

previous 14.99 ) but once i touch the accel pedal, it sticks to 0!

 

Fuel learn has multiple different ranges, and very likely when you press the accelerator, you're in a range where the learn is at 0%.

[Volta55]

Fuel learn has multiple different ranges, and very likely when you press the accelerator, you're in a range where the learn is at 0%.

 

are you talking about OP's post?

 

http://legacygt.com/forums/attachment.php?attachmentid=248778&thumb=1&d=1494032690

 

in the vertical column of MAF g/s 0.0, my learn % is at 9... but my next 3 vertical columns are 0.0

 

im still learning BTSSM...sry lol

[xt2005bonbon]

If you are not familiar with what this table is showing, here are good threads explaining what this all means.

 

http://www.romraider.com/forum/topic2772.html

 

http://www.romraider.com/forum/topic4899.html

 

http://www.romraider.com/forum/topic5371.html