09-08-2019, 09:45 AM
|
#1
|
|
Registered User
Join Date: Aug 2019
Location: Mi
Posts: 69
|
Vacuum leak - smoke test shows smoke coming from under the air oil sperator
Does that mean the AOS needs to be replaced? Or is there a hose underneath there? I cant really tell exactly where it is coming from.
|
|
|
|
09-08-2019, 10:34 AM
|
#2
|
|
Registered User
Join Date: Aug 2019
Location: Mi
Posts: 69
|
Upon further inspection, I think it is the air oil separator boot that has come off underneath.
Has anyone replaced this before? Any tips?
There was a screw type hose clamp on it so I think that means somebody has messed with it before. Not a spring type hose clamp.
|
|
|
|
|
09-08-2019, 11:22 AM
|
#4
|
|
Who's askin'?
Join Date: Mar 2018
Location: Utah
Posts: 2,448
|
Quote:
Originally Posted by Starter986
|
Pretty sure I've got one of these floating around in a box someplace, still in the bag. It's yours for postage, if I can find it.
Sent from my SM-G970U using Tapatalk
|
|
|
|
|
09-09-2019, 10:21 AM
|
#5
|
|
Registered User
Join Date: Oct 2008
Location: O.C. CA
Posts: 3,709
|
Quote:
Originally Posted by Starter986
|
AOS diaphragm has been vertical since 1998
__________________
OE engine rebuilt,3.6 litre LN Engineering billet sleeves,triple row IMSB,LN rods. Deep sump oil pan with DT40 oil.
|
|
|
|
|
09-09-2019, 10:44 AM
|
#6
|
|
1998 Boxster Silver/Red
Join Date: Sep 2017
Location: 92262
Posts: 3,071
|
Quote:
Originally Posted by BYprodriver
AOS diaphragm has been vertical since 1998
|
I replaced my AOS a while back... and it was horizontal. The new/updated one I installed the diaphragm was vertical.
Did Porsche come out with that update the same year of production? Was the car manufactured with both versions? I'm curious.
__________________
1998 Porsche Boxster
|
|
|
|
|
09-09-2019, 12:51 PM
|
#7
|
|
Registered User
Join Date: Aug 2019
Location: Mi
Posts: 69
|
Pulled the AOS today. Pretty easy job. The lower hose quick connector was already broken from the last guy (he owned a shop) but it seems to be sealing fine.
I inspected the bellows and besides the fact that it seems out of shape (maybe from heat) I was able to reinstall and tighten a screw type hose clamp but I don’t like the fact that there is no lip on the metal fitting the bellows goes on to. Seems like it can easily come off again in the future.
The AOS was a uro parts one so obviously replaced before. Previous owners used cheap parts all over this car. For example the brake rotor hats are all rusted. Annoying.
Smoke test after was good. No smoke and the system seemed like it was holding a bit of pressure.
I pulled the negative terminal of the battery to try and reset the ECU. Let it stay disconnected for about 10 mins. When I reconnected it the car ran really rough, missing and knocking a bit (through the intake). I would have though that would reset the fuel trims and it should have ran a lot better initially? Ended up smoothing out after a minute and runs good now. No check engine light yet.
What is the proper way to reset fuel trims or ecu on this vehicle?
I think I’ll leave the uro AOS in there but maybe put on a OEM bellows. Any opinions? There was a little bit of oil in the intake but no smoke out the exhaust.
|
|
|
|
|
09-11-2019, 10:48 AM
|
#8
|
|
Registered User
Join Date: Oct 2008
Location: O.C. CA
Posts: 3,709
|
Quote:
Originally Posted by Starter986
I replaced my AOS a while back... and it was horizontal. The new/updated one I installed the diaphragm was vertical.
Did Porsche come out with that update the same year of production? Was the car manufactured with both versions? I'm curious.
|
I believe it was phased in late 1998.
My Motorsport AOS has a horizontial diaphram.
__________________
OE engine rebuilt,3.6 litre LN Engineering billet sleeves,triple row IMSB,LN rods. Deep sump oil pan with DT40 oil.
|
|
|
|
|
09-09-2019, 04:07 PM
|
#9
|
|
1998 Boxster Silver/Red
Join Date: Sep 2017
Location: 92262
Posts: 3,071
|
Quote:
Originally Posted by BYprodriver
AOS diaphragm has been vertical since 1998
|
This was the type, horizontal, that I removed from my car replacing it with the newer/most current part, vertical. I had read that the horizontal diaphragm would often quickly fail on the horizontal model, so the part was modified with the diaphragm vertical.
Are you saying that when the car was manufactured the factories were installing both versions?
Thank you.
__________________
1998 Porsche Boxster
|
|
|
|
|
09-11-2019, 04:22 AM
|
#10
|
|
1998 Boxster Silver/Red
Join Date: Sep 2017
Location: 92262
Posts: 3,071
|
Quote:
Originally Posted by Starter986
This was the type, horizontal, that I removed from my car replacing it with the newer/most current part, vertical. I had read that the horizontal diaphragm would often quickly fail on the horizontal model, so the part was modified with the diaphragm vertical.
Are you saying that when the car was manufactured the factories were installing both versions?
Thank you.
|
BYprodriver, did I stump you or are you still scouring the interwebs looking for the content that will substantiate your claim?
__________________
1998 Porsche Boxster
|
|
|
|
|
09-08-2019, 12:48 PM
|
#11
|
|
Certified Boxster Addict
Join Date: Nov 2010
Location: Los Angeles
Posts: 7,669
|
Quote:
Originally Posted by Vtx531
Upon further inspection, I think it is the air oil separator boot that has come off underneath.
Has anyone replaced this before? Any tips?
There was a screw type hose clamp on it so I think that means somebody has messed with it before. Not a spring type hose clamp.
|
This happened to my Boxster at the race track last month. Doesn't matter if its the OEM spring or an aftermarket screw type, the fix is the same - just re-attach the tube/boot and make sure that the clamp is fully engaged to hold it in place.
__________________
1999 996 C2 - sold - bought back - sold for more
1997 Spec Boxster BSR #254
1979 911 SC
POC Licensed DE/TT Instructor
|
|
|
|
|
09-08-2019, 05:11 PM
|
#12
|
|
Registered User
Join Date: Aug 2019
Location: Mi
Posts: 69
|
Quote:
Originally Posted by Starter986
|
Very informative thank you. It seemed like the boot was extremely pliable (that what you meant about butter) and very loose on the mounting. Like if I reused it would be similar to having pants that are way too big and then you cinch up the belt really tight - doesn’t work well.
Quote:
Originally Posted by maytag
Pretty sure I've got one of these floating around in a box someplace, still in the bag. It's yours for postage, if I can find it.
Sent from my SM-G970U using Tapatalk
|
That would be great! Let me know
Quote:
Originally Posted by thstone
This happened to my Boxster at the race track last month. Doesn't matter if its the OEM spring or an aftermarket screw type, the fix is the same - just re-attach the tube/boot and make sure that the clamp is fully engaged to hold it in place.
|
Glad to hear it sounds like not a really bad job thanks.
|
|
|
|
|
09-23-2019, 10:50 AM
|
#13
|
|
Registered User
Join Date: Aug 2018
Location: Woodland Wa
Posts: 1,300
|
VTX531
Question?????
When you did the smoke tests on the car did you remove the MAF sensor?????
They can be very sensitive to contaminants.
|
|
|
|
|
09-23-2019, 11:18 AM
|
#14
|
|
Registered User
Join Date: Aug 2019
Location: Mi
Posts: 69
|
Quote:
Originally Posted by blue62
VTX531
Question?????
When you did the smoke tests on the car did you remove the MAF sensor?????
They can be very sensitive to contaminants.
|
I did not, but I removed the pipe between the MAF and throttle body and introduced the smoke at the throttle body.
****I think (hoping) the problem is solved****
I disconnected the battery for about 1 minute, pressed brake, reconnected, and did ignition on for one minute and off for 10 seconds.
This cleared the codes and reset the long term trim to zero. It ran great right off the bat (unlike before when I only cleared the codes using the scanner). Numbers seem good now at idle and when revved.
Idle:
STFT1 +3.13%
STFT2 +2.34%
LTFT1 -0.78%
LTFT2 -0.78%
Last edited by Vtx531; 09-23-2019 at 11:31 AM.
|
|
|
|
|
09-23-2019, 12:06 PM
|
#15
|
|
Registered User
Join Date: Aug 2019
Location: Mi
Posts: 69
|
Not solved!!! 
I took it out for a drive and could barely make it around the neighborhood. When giving it gas, the short term trims were pegged at +25% and eventually the long term trims settled above 30% again.
Midway through when idling I was seeing:
STFT1 -19.53%
STFT2 -19.53%
LTFT1 +21.88%
LTFT2 +20.31%
Maybe a fuel delivery issue??
|
|
|
|
|
09-23-2019, 01:53 PM
|
#16
|
|
Registered User
Join Date: Aug 2019
Location: Mi
Posts: 69
|
Fuel pressure test:
Key on ignition: 42-46 psi. Out of spec. Manual says between 52-58
Idling: 47 psi. In spec. Manual says 46-52psi
When revved in neutral throughout the rpm range the pressure is pretty steady within specs.
Thoughts???
Last edited by Vtx531; 09-23-2019 at 01:58 PM.
|
|
|
|
|
09-23-2019, 02:22 PM
|
#17
|
|
Registered User
Join Date: Aug 2019
Location: Mi
Posts: 69
|
I drove around with the MAF disconnected while monitoring the live data.
It seemed to run better with MAF disconnected. The short trims were going negative 20’s under acceleration and trying to balance out the +32% long trims.
When I reconnected the MAF it was adding more positive fuel to the short trims on top of the +32% long trims.
Bad MAF?
|
|
|
|
|
09-23-2019, 05:55 PM
|
#18
|
|
Registered User
Join Date: Aug 2018
Location: Woodland Wa
Posts: 1,300
|
Quote:
Originally Posted by Vtx531
Fuel pressure test:
Key on ignition: 42-46 psi. Out of spec. Manual says between 52-58
Idling: 47 psi. In spec. Manual says 46-52psi
When revved in neutral throughout the rpm range the pressure is pretty steady within specs.
Thoughts???
|
not sure what to think on that. in spec on idle is a positive at least it shows that the injectors are getting correct pressure.
under spec. at key on test is the head scratcher. I believe the key on test is to check that the system is pressurizing properly for initial start up. (That is a guess on my part.)
You had not said anything about starting issues so maybe the low spec is not an issue????
|
|
|
|
|
09-24-2019, 05:41 AM
|
#19
|
|
Registered User
Join Date: Aug 2019
Location: Mi
Posts: 69
|
Well here is this morning’s tinkering...
I took out the MAF and cleaned it. Reinstalled it and reset the ecu. Short term fuel trims were pegging at +25%. I am guessing that is the maximum it can do. Car had no power, hesitation, ran badly.
Then I unplugged the MAF and it ran great and never go above +10% on the short term fuel trims.
So I am thinking MAF sensor and hopefully it is not an issue with the MAF wiring.
|
|
|
|
|
09-24-2019, 06:34 AM
|
#20
|
|
Registered User
Join Date: Aug 2018
Location: Woodland Wa
Posts: 1,300
|
With the MAF plugged in the car runs poor because it is getting a signal or value from the MAF that is wrong or implausible, out of range what ever.
When you unplug the MAF sensor the ECU-DME no longer gets a signal (or value) from the MAF. So the ECU-DME substitutes a value and that forces fuel system to go to a set fuel map. which in turn allows the car to run.
A long way of saying the ECU-DME is recognizing that the MAF signal is missing. So the wiring should be good.
So between the two of us I would say we have pinned it down to a faulty MAF sensor 
The proof will be when you spend the big bucks and replace it.
Let me know the outcome.
Last edited by blue62; 09-24-2019 at 06:39 AM.
|
|
|
|
| Thread Tools |
|
|
| Display Modes |
 Hybrid Mode
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is On
|
|
|
All times are GMT -8. The time now is 12:26 PM.
| |
Mean Motor Scooter
