98 S70 T5: Peculiar vacuum leak after engine swap

[WhatAmIDoing]

Firstly, I'm not dead (yet). Secondly I need to get this car running and driving ASAP.

I've been chasing vacuum leaks and poor electrical connections since completing the engine swap. One leak I can't seem to trace appears to be originating near the PTC. There is an extremely audible hissing noise. I thought I traced the leak, but everything I've done has failed to correct it. If I pinch off the vacuum line at the PTC that leads back to the passenger side of the manifold, the hissing stops and the rpms drop.

So I've tried all the following with no resolution:
I cut off the last inch of the vacuum line to remove superficial damage and installed a new hose clamp.
I removed the breather hose and plugged the PTC with my finger to see if the hissing stopped. Nope.
I checked the clamps on all the vacuum lines near the turbo and from the intake tube.
I smoked the intake and found a leak at the PTC and turbo flange. I replaced the intake tube and PTC with another off the parts shelf. No change (might even be worse now). I Smoked the intake tube before installing and it was holding pressure.

I'm at a loss now. I still cannot quite pinpoint the source of the leak. Initially I thought it had something to do with replacing the stock breather tube with 5/8 coolant hose. But I'm very confident I ruled that out. Perhaps both PTC nipples and grommets are bad. I've ordered new ones. Now I'm once again asking all you wonderful forum members for ideas before tearing the entire intake and pcv system apart again.

All I can think left to try is to replace the entire vacuum hose from the intake to PTC again. I think I can possibly accomplish this without removing the intake, but if it fails I will be stuck removing the intake again and was hoping to avoid this.

If I end up removing the intake, I'm going to replace the hoses with copper this go around.

[scot850]

Try smoking the intake. A common mistake is when refitting the intake is to trap the hose clamp for the PCV hose between the RH end (when viewed from the front of the car) between the intake and gasket. You may not have done that but worth a check.

Based on the general area of the issue, have you check the vacuum pipe for the TCV that run to the turbo?

Does the turbo boost correctly? It may be a wastegate diaphragm split?

Neil.

[WhatAmIDoing]

Try smoking the intake. A common mistake is when refitting the intake is to trap the hose clamp for the PCV hose between the RH end (when viewed from the front of the car) between the intake and gasket. You may not have done that but worth a check.

Based on the general area of the issue, have you check the vacuum pipe for the TCV that run to the turbo?

Does the turbo boost correctly? It may be a wastegate diaphragm split?

Neil.

I did smoke the intake from the throttle body, but may be worth doing again. Didn't find any leaks.

I checked the vacuum lines for the turbo and TCV. I will try swapping the TCV to a known good, but I doubt that's the issue.

Haven't been able to really test boost yet. It seemed to boost fine on the first test drive but it stated running rough a while after. I really should've checked the diaphragm and CBV before installing the turbo. I will find my vacuum hand pump and try the wastegate actuator adjustment procedure. I'm assuming if it doesn't hold pressure that's bad.

[WhatAmIDoing]

Try smoking the intake. A common mistake is when refitting the intake is to trap the hose clamp for the PCV hose between the RH end (when viewed from the front of the car) between the intake and gasket. You may not have done that but worth a check.

Based on the general area of the issue, have you check the vacuum pipe for the TCV that run to the turbo?

Does the turbo boost correctly? It may be a wastegate diaphragm split?

Neil.

I tested the the WG actuator under vacuum and pressure. It's holding.

I smoked the intake directly and from the maf. Had to crank the test pressure all the way up to find smoke anywhere. #1 fuel injector is sealing poorly but there's no detectable vacuum leak there with ether or propane (I planned on having the injectors cleaned and tested so I bought a seal kit). The new intake tube wasn't making a perfect seal on the turbo flange but some fiddling fixed that. Biggest was discovering my intercooler is failing at the crimp to the plastic tank. But again I tested with propane and ether (and ear) and couldn't detect a vacuum leak.

Still haven't found the source of the hissing. Sounds like an induction leak on a big truck. It's very loud. Not sure what else to do around the turbo for testing. I still find it odd pinching off the one line with manifold vacuum will stop the noise but no leak can be detected. I'm stumped and ready to give up on this project for another year.

[scot850]

What vacuum line are you pinching that stops the hissing? that may give us a clue where to check next.

Neil.

[WhatAmIDoing]

What vacuum line are you pinching that stops the hissing? that may give us a clue where to check next.

Neil.

Oops my brain typed faster then my hands. It's the line from the manifold to the PTC that runs along the large crankcase vent hose. I thought it could be the grommet or the ptc so I swapped both out and pressure tested the intake tube before installing. No change. I've pinched off the vac hose at the manifold and at the intake and everywhere accessible in the middle. Every time the hissing stopped. So I don't think it's the hose. I even removed the vent hose and plugged the hole. Still hissing. Garden hose ear says the noise is isolated to the turbo /bottom of intake tube area.

I've checked, rechecked, and replaced just about everything with no difference to be made. I really need this car working by the weekend to escape the next round of flooding. Now I'm just hoping it will limp to the top of the hill.

[scot850]

Have you checked for cracks in the turbo or any gaskets?

It is strange that clamping that hose to the PTC has such an effect. I wouldn't have expected such a pressure release from the PCV system.

I know you said the intake hose was solid now, are you sure it is not cracked or where it bolts to the turbo is not damaged?

Neil.

[abscate]

removed the breather hose and plugged the PTC with my finger to see if the hissing stopped. Nope.

Okay, so the leak is on the snorkel. Get it off and up on the bench and inspect it fir cracks and damage. It has to fit right on the turbo, and get cinched down tight. There is an index tab on it that has to slide into a receiving area on the turbo. Close doesn’t count

[WhatAmIDoing]

I replaced the intercooler after discovering a failed crimp. This was definitely causing a large intake leak. After putting everything back together and resetting the fuel trims, I was surprised to see that it now runs worse than before. Fuel trims immediately maxed out at -25.5, set a P0172 (too rich). I took everything back apart to inspect hoses and fittings. Smoked the car again and discovered no leak. Reset the computer. Fuel trims maxed out again at -25 but this time set a P0171 (too lean) code. Tore everything back down again. Reseated the ecu, cleaned and reseated the O2 sensors and MAF connectors, reset the fuel trims, and replaced the fuel pump relay because why not.

This most recent test drive went different. Started and idled good, O2 sensor was fluctuating between .4 and .6 V (which I believe is very good). Started the drive and it started hesitating. O2 sensor reading low <.3V (very lean). After driving and idling a short while, O2 started reading what I think is normal, fluctuating between .8 and .3 V. LTFT was reading around -1.6. Car felt good, but maybe a little low on power. Then the fuel trims started getting wacky fluctuating from 1V all the way down to .01V. Smelled like it was running very rich. LTFT back near -10 with hesitation and poor idle. Occasionally it seems to fix itself for a bit and run good before going back to running too lean or too rich.

Still hear the mysterious hissing noise. Vacuum at idle is lower than I believe it should be at 18mmHg +/-2. Car has been smoked at least 2 dozen times now. I keep looking for a vacuum leak but can't find one. Starting to think this is a red herring. Can't seem to find any correlation in the live data that points to any one thing. I've ordered a new selection of high quality vacuum line and hoses. I'm just going to re-replace everything so all of it is 100% new vacuum line. Also ordered the IPD HD fuel injector O-rings to see if that helps.

Getting to the point now where I'm talking myself into dropping $150 on a new O2 sensor and maybe another $200 on new reman injectors. Wondering if anyone has any ideas to try? What can look like a vacuum leak but not be a detectable vacuum leak with a smoke machine? Not sure if any of this rambling will make sense to anyone, it's late. Been at this for hours everyday the past 3 months.

[abscate]

When Im really frustrated I call a friend over to find my stupid mistake, it has to be something simple. Have you had the snorkel off to clean and inspect?