Vacuum leak, but no boost leak?

[vbt101]

I recently installed the PTP IM spacer, EGR delete, TB bypass & injector seals. Now my fuel trims are crazy (+25 at part throttle). My idle trims were 0 before the install, but now they are around +5.

I used an air compressor and did a boost leak test at the hot side of the FMIC and it was able to hold 20psi just fine. Driving it, the car holds 20psi just fine. I very carefully redid the intake -> turbo side of things 3 times already with no change.

It may still be the intake, but I've redone it a number of times, and I didn't have this problem before the installs, so I have a hard time believing there is an issue there.

Anybody have thoughts on this? What could leak under vacuum, but not boost?

[phillyb]

i had a similar thing happen when i installed a tb spacer.
car was super lean at idle, but ran just fine once at a certain rpm.
took the spacer off, no more problems.
i know it's a pita or whatever, but see what happens if you take off the im spacer.

[vbt101]

You think the IM spacer could still be an issue after the boost test?

Is it likely that this is related to the injector seals? Like maybe the injectors arent seated correctly?

[phillyb]

yeah, i have no idea.
good luck

[R.MS3]

Might be your purge valve crapping out.

[vbt101]

Sweet. I have an extra one of those. I'm not really clear on their functionality. Don't they only affect at idle?

[Shanems3]

flux capacitor is going out.....




seriously, if you think you have a vaccuum leak, get some carb cleaner and spray it on the suspected area of the leak.. if the idle bumps up, there is you leak..

[vbt101]

Is carb cleaner bad for hi-temp paints? I suspect it will jack up my IM paint if I try to spray anything on it. I can try it on some of the other areas though.

[Shanems3]

o yeah, it will strip paint... i use it to spray on vacuum lines and along the intake manifold and head for supected leaks..

[vbt101]

is it possible that leaky/improperly seated injectors are causing this? my fuel pressure definitely goes up over 1700....i havent checked it at WOT to see if it holds though. kinda makes me nervous trying though. I'm getting a CPe CAI in this week, so hopefully that puts to bed any weird MAF curve issues & reduces all those leak-prone couplers..

[bova]

perhaps there is something loose on your intake manifold. check the hose that goes from the pcv to the back of the intake manifold.

[R.MS3]

A little off-topic from this one but in the same "area"...

Has anyone checked their LTFT when STOCK? I recently had to put my back back to stock to take it to the dealer and i noticed on stock tune/stock car, my trims sometimes reached almost +9% when accelerating and +4% when idle.

Vaccum seems good at -20/-21 and i think it's holding boost well so i was just wondering what other people has experienced. Just a note, when i put my SRI on a stock tune, trims went to +20% w/ a CEL as well.

[phillyb]

op, you get this fixed yet?

[vbt101]

sorry guys, had some people visiting this week. ill get back on this tonight. i'll keep the thread updated as i check/find things. hopefully it'll help someone else in the future.

Originally Posted by ReNaToMS3 A little off-topic from this one but in the same "area"... Has anyone checked their LTFT when STOCK? I recently had to put my back back to stock to take it to the dealer and i noticed on stock tune/stock car, my trims sometimes reached almost +9% when accelerating and +4% when idle. Vaccum seems good at -20/-21 and i think it's holding boost well so i was just wondering what other people has experienced. Just a note, when i put my SRI on a stock tune, trims went to +20% w/ a CEL as well.

I haven't checked when I was stock, but I bet there is an air leak causing this. If you're stock, the bypass valve leaks. Also, the stock turbo inlet pipe is junk, and is often not clamped onto the turbo correctly. I read an old post somewhere on here where the guy had the SRI installed and said his car ran like trash and the trims were high. Once he got the turbo inlet pipe as well, his trims went from 18-20 down to 8 and his car was fast again.

Originally Posted by ReNaToMS3 Might be your purge valve crapping out.

It seems to be working fine. Also, swapped in my old one, which was working fine as well. No change.

[Lex]

Are you able to get a log showing STFT, LTFT, MAF voltage, AFR as you slowly increase load from idle to boost?

A leak between your MAF and the turbo will cause high LTFTs at all times.

A leak between the turbo and engine itself will have high LTFTs at idle (vacuum) but negative LTFTs under boost - this is especially pronounced if it's between the throttle body and intake ports. Is this the scenario you are seeing? It appears like there's a leak at the manifold to motor interface (after the throttle body) and the gasket is the most suspect.

[vbt101]

Thanks, Alex. Always learning from you. I'll post a DH log of all of these things tomorrow as soon as I can.

[R.MS3]

If that's for me, sure I can. Up to 28g/s, ltfts seem pretty steady at 3 to 4%, sometimes even 2. As you go past 28g/s, trims jump to 8-9%. Didn't really do a wot log yet.

If you have a leak and a calibrated maf via atr, would the trims keep going up to cel range? Reason I ask is when I had the tune done the trims would barely move up or down.

[vbt101]

Originally Posted by Lex Are you able to get a log showing STFT, LTFT, MAF voltage, AFR as you slowly increase load from idle to boost? A leak between your MAF and the turbo will cause high LTFTs at all times. A leak between the turbo and engine itself will have high LTFTs at idle (vacuum) but negative LTFTs under boost - this is especially pronounced if it's between the throttle body and intake ports. Is this the scenario you are seeing? It appears like there's a leak at the manifold to motor interface (after the throttle body) and the gasket is the most suspect.

I tried to get a slow pull from idle to max boost, but once I got above 5psi (I have a SB so it's clipped to 5psi), the boost pins pretty quickly...so the log seems a little messy to me. Let me know if it doesnt have enough information to infer anything from and I can take another. Looks like the trims are high all the time, so based on what you said, it's a pre-turbo leak. Is that correct? Can we rule out the IM gasket? What about fuel injector leaks?



http://lh6.ggpht.com/_9GBImNFI4t8/S8...low%20pull.jpg

[Lex]

Hmm you have a SB. Did you adjust the MAF calibration at all or remove/reinstall the harness? Your STFTs should drop to 0 when WOT - do they ever do this?

The injectors won't leak in the same way port injectors leak since the leak will be directly in the combustion chamber. You would hear them if they leaked.

[vbt101]

Out of curiosity, what will the injectors sound like if they leak? I don't hear anything out of the ordinary as my STFTs rise with the throttle opening, so I bet they are fine.

1. I didn't do any MAF calibration before/after the install.
2. I DID remove the SB Harness though.
3. STFTs do drop to 0 at WOT. What would cause them to not? Not enough MAP built up?

[Lex]

Crackling and popping is what the injectors sound like when they leak and you get KR.

Perhaps the issue is with the SB altering the MAF signal slightly. Remove the SB and PNP harness. Idle the car and see if STFTs/LTFTs fall more into place.

[vbt101]

Damn. Alright, tried that & the trims reacted in roughly the same way with and without the PNP/SB.

I'm gonna try replacing the intake with a CPe CAI and switching my BOV to VTA (that recirc tube always looks like it has a sketchy joint with the BOV & its one of the few remaining leak prone areas I'm gonna have).

Lex, do you think it makes sense to go this route or do you think there are smarter things I can try?

[Lex]

I think you should focus on the things that you did before this change happened.

I would focus here:
PTP IM spacer, EGR delete

Also by TB Bypass do you mean you removed the coolant from going through the TB? I hope you don't live in a very cold climate.

[vbt101]

Man, I bet it's the EGR delete. That block-off cap didn't seem to want to seat flush. I remember wondering if it would seal properly. It def looked like it pressed against the block okay, so I assumed it was good. I'm gonna see if I can find the leak with propane, as soon as I get some.\\

Originally Posted by Lex Also by TB Bypass do you mean you removed the coolant from going through the TB? I hope you don't live in a very cold climate.

That is what I mean. I live in DC. It gets below freezing in the winter. Is that bad?