Hear A Boost Leak but Where is it?

[pSimytSi]

So for the past week I've been having some sputtering issues at WOT, I think from a boost leak. Now, for the past 2 days I'm having almost the same problem while cruising a steady speed. While cruising, no certain speed or even rpms, sometimes the AFR gauge goes in the red to 18+ and the car sputters continuously. The only thing I found that stops it instantly is to engage/disengage the clutch or downshift..

Right now my ISC is bad, my FPS is bad, and I'm running the 255lph with stock FPR. It also has a big boost leak comming from under the throttle body elbow or around the ISC somewhere, but I can't seem to find it. It takes 3-5 seconds after pressurizing from the turbo inlet, and all that air is leaked out from somewhere under the TB elbow.

I know all these problems added together must be causing most of this so can you guys just point me in the right direction as to what will do what and where to find that huge boost leak?

Please help, I'm a newb but learning!

 

[snowborder714]

Spray soapy water on an area that you're testing. This will help you "see" the leak(s) as the soap will bubble up where air is leaking out.

 

[mitsu93gsx]

Make or buy a leak down tester, Pressure the system up with a air compressor like 20 psi and see and hear where all the air is coming out and replace faile o rings and gaskets.

 

[pSimytSi]

Spray soapy water on an area that you're testing. This will help you "see" the leak(s) as the soap will bubble up where air is leaking out.

Thanks I'll try the soapy water again, but with more soap this time. I tried this already but was scared of getting water into the wires/sensors so didn't really spray around alot. It won't short anything around there will it?

 

[mitsu93gsx]

http://www.dsmtuners.com/forums/new...se-troubleshoot-boost-leak-tester-merged.html

 

[mitsu93gsx]

Here are some different threads that might help you.
http://www.dsmtuners.com/forums/search.php?searchid=5489219

 

[Calan]

As for the TB leak... check the shaft seals. That is a very common leak source. It could also be the injector seal closest to the TB; those like to get hard and fail too. Your problem seems to be an intermittent boost leak...which again points to the TB seals. Mine used to leak only when the throttle plate was at certain positions.

You said "AFR gauge goes in the red to 18". Is this a true AFR gauge, or one of those narrowband (and useless) dash ornaments? Did you mean 18:1? It will go lean on decel and in a couple other situations, but if it just jumps to 18:1 under steady cruise for no apparent reason, something is definitely not right.

A post-MAF boost leak would normally cause a rich condition while in boost, because you are loosing air that the ECU is expecting; therefore you end up with more fuel than air. Under vacuum (just cruising around or at idle), the opposite can happen; the engine pulls in unmetered air through the leak, causing a lean condition. A true AFR of 18:1 is lean. Are you in boost or steady cruise when the AFR jumps?

After fixing all boost leaks, I would check and/or replace the O2 sensor.

 

[pSimytSi]

You have some other issues though. You said "AFR gauge goes in the red to 18". Is this a true AFR gauge, or one of those narrowband (and useless) ornaments? Did you mean 18:1?

if it just jumps to 18:1 under steady cruise for no apparent reason, something is definitely not right. A post-MAF boost leak would normally cause a rich condition, because you are loosing air that the ECU is expecting; therefore you end up with more fuel than air. A true AFR of 18:1 is lean...just the opposite.

Check and/or replace your O2 sensor.

I believe it is a true AFR guage? I'm not sure on the brand, but it reads from 10.0-18.0..

By 18+ I say this because anything over 18 it just shows 3 red dashes like this - - - and it is happening while holding a steady speed not from deceling. Could it be my fuel pump is going/fuel injectors, or because of the stock fuel pressure regulator? Maybe the FPR is shot too from being over worked by the 255lph? This particular problem started happening after a hard pull in 2nd and 3rd gear yesterday.. I wish I had more restrain until it was 100% fixed and tuned but..

 

[Calan]

It could be any number of things. Do you have a datalogger? It will be really hard for us to help diagnose your problem without being able to look at some logs and see what is going on with your engine.

Besides the boost leaks (and all the normal maintenance stuff such as base timing, etc), here are some things I would check (in semi-order of what I would suspect):

1. O2 sensor
2. leaking PCV valve
3. clogged fuel filter/injectors/dirty gas/sediment in the lines or tank

And yep... that would be a true AFR gauge; you're all set there

 

[pSimytSi]

It could be any number of things. Do you have a datalogger? It will be really hard for us to help diagnose your problem without being able to look at some logs and see what is going on with your engine.

And yep... that would be a true AFR gauge; you're all set there

Yeah I've yet to get a datalogger but it's on the very near to get list. I had planned on getting a new ISC and FP Solenoid this weekend along with getting the ECU fixed if the ISC driver is burnt out. This would hopefully clear up my idle problems. Then next week or so would be the datalogger and wideband 02.

Now it seems like the problems are spreading faster than they can be diagnosed.

 

[No_Skillz]

You need an AFPR for the 255. It's not being "overworked," it just doesn't allow enough fuel to flow back into the tank so you are running way rich.

 

[snowborder714]

Spray the soapy water liberally. I have done this multiple times in a row without any negative effects. If you are a little scared, then let it dry before you start up the car.

Yes, you have a wideband o2 sensor. This will tell you a specific numeric air/fuel ratio. This should be reading around 14.7:1 at idle and cruising. Then it'll vary what it reads when you're at WOT. If no adjustments have been made, it will be around 9.4:1 or so. If proper adjustments have been made, it'll be around 11:1.

I would do a boost leak test and make sure to check all of your couplers really well. Then start working out your issues that you mentioned in your first post.

 

[pSimytSi]

You need an AFPR for the 255. It's not being "overworked," it just doesn't allow enough fuel to flow back into the tank so you are running way rich.

It actually hardly ever runs really rich. Well if really rich is in the 10.0 range. At a certain rpm while at max boost it drops to 10.2ish but that's the only time. For the most part under boost it ran low 11.x And my safc2 settings are programmed by me with the help of some members here and the guide at rre so it may just be a bit off there.


Snowboarder, I have or I need a wideband 02? I believe the one(s) in it is stock but honestly have no idea. From the BLT I did a few days ago the only leak, or it may just be so big I couldn't hear any other ones, was comming from under the TB elbow. I'll be testing it again today though with soapy water.

 

[Calan]

You apparently already have a WB, so you're good to go there.

Testing and fixing boost leaks is a cyclic process. Air will always take the path of least resistance, so as you fix one leak, another smaller one will show up. Just keep at it until you can hold steady pressure; shoot for 20psi holding at around a minute or so...that's a good start.

Oh yeah... check your base fuel pressure too. Should be around 43 psi on your 2G I believe.

 

[pSimytSi]

You apparently already have a WB, so you're good to go there.

Great news to me if it's true! Is it only a wideband that can display these readings on the AFR gauge? I'm stumped on this one, I thought for sure I needed one.

 

[Calan]

Mike and others may flame me for this, but...

If I was on a budget and in your shoes I don't know if the AFPR would be high on my list. I think they are necessary for high pressure pumps, but I wouldn't consider it as urgent a need for you, if fundage is tight...especially if you don't seem to be running rich all the time (and you said it's a 255Lp right?). Depending on what you tune with, you could always lower the base fuel pressure a bit if absolutely necessary...although I wouldn't unless you were really rich and knew for sure that you were over-running the fuel rail/injectors.

Once you get the priority stuff taken care of, I would definitely install a good AFPR. I use an Aeromotive myself; they are pretty popular, inexpensive, and easy to install.

Just IMHO of course

 

[Calan]

AFR devices come in two varieties; narrowband (NB) and wideband (WB). Your stock O2 sensor is a narrowband device. It's voltage output varies over a "narrow" range, centered around a stoich mix which is 14.7:1. So the sensor won't accurately read any AFR outside of this narrow range. Those flashy LED meters are NB, and therefore useless when tuning.

Widebands vary their output over a (you guessed it) wider range of air/fuel ratios. So they can read from around 10:1 up to whatever (most are around 18:1 I think). A wideband sensor normally plugs into a control box of some type, which converts the sensor voltage and supplies it to a gauge or an extra ECU input for logging. Many of the WB units also have other inputs so you can wire up boost (MAP) sensors, EGT sensors, etc., and many if not all also have their own logging software.

 

[pSimytSi]

Mike and others may flame me for this, but...

If I was on a budget and in your shoes I don't know if the AFPR would be high on my list. I think they are necessary for high pressure pumps, but I wouldn't consider it as urgent a need for you, if fundage is tight...especially if you don't seem to be running rich all the time (and you said it's a 255Lp right?). Depending on what you tune with, you could always lower the base fuel pressure a bit if absolutely necessary...although I wouldn't unless you were really rich and knew for sure that you were over-running the fuel rail/injectors.

Once you get the priority stuff taken care of, I would definitely install a good AFPR. I use an Aeromotive myself; they are pretty popular, inexpensive, and easy to install.

Just IMHO of course

I don't know about them but I'll congratulate you for trying to help me! Funding is a little tight as I just bought the car (I've only had it 3 weeks) and in doing so I fell behind on all my bills! Having this car in my garage came first.
I tried to check the fuel pump last night to make sure it is a real 255 but couldn't get the tank cap off to see it. So far everything is what he said it was though.

How do I check the base fuel pressure without an afpr?

 

[Calan]

DOH!

... ummm... I guess that's a good point. There are ways to do it, but I was thinking more along the lines of compensating for it with injector parameters and such. I wasn't thinking clearly; that is all beyond what you are working with at this point...You have enough to learn/worry about right now

I would just get everything fixed that you know for sure needs to be done (and get a logger!), and then get an AFPR when funds allow it or if you know you are definitely over-running.

EDIT:

The reason I mentioned "255Lp" is because back when I bought my 255, they offered both a high-pressure (255hp) and a low-pressure (255lp) version of it (do they still?). I was thinking if you had the lp version, fuel over-run probably isn't as much of an issue.

 

[snowborder714]

Don't worry about checking base fuel pressure if you don't have an AFPR. Even if it's wrong, what are you going to do to fix it?

Here's a picture of a wideband o2 gauge, so you can compare yours. You have one from your description which is good. I would hope you wouldn't be tuning without one.

You must be logged in to view this image or video.

To check the fuel pump, all you should have to do is unscrew 4 phillips head screws to remove the cover for the fuel pump (which is under the rear passenger's seat). Then remove the housing unit.

 

[pSimytSi]

Don't worry about checking base fuel pressure if you don't have an AFPR. Even if it's wrong, what are you going to do to fix it?

Here's a picture of a wideband o2 gauge, so you can compare yours. You have one from your description which is good. I would hope you wouldn't be tuning without one.

You must be logged in to view this image or video.

To check the fuel pump, all you should have to do is unscrew 4 phillips head screws to remove the cover for the fuel pump (which is under the rear passenger's seat). Then remove the housing unit.

That guage looks pretty similar except mine dosn't say wideband. It does display the numeric value and have the LED bars surrounding the display though. And it does read from 10-18. So that's a plus, one thing to cross off the list.

I got that cover off just couldn't loosen that big housing unit 'lid'. I gave up before grabbing any tools to help me, but not before my hands became sore from trying. I have good reason to be in the garage the next couple days.

 

[pSimytSi]

So I'm going to go outside and start checking some of these things over while there's daylight left. I might order a datalogger tonight after doing some more research on what they can do.

So thanks for all the replys, each one has brought me one step closer!



Edit: So I think the sputtering while it was being ran hard is fixed. I found a rubber vac line under the TB, I believe going to the EGR was torn at the end, you can say off the nipple. Sence this fix I've taken the car out a few times and it hasn't happened.

It's still lean-sputtering some times when cruising around though, so that sucks.

 

[pSimytSi]

I ended up finding my boost leak, I still don't know what's causing it.

It's leaking from straight under the Throttle body elbow directly between the ISC and that roundish port right beside it where the coolant line connects to the intake. There's like a 1/4" gap between the ISC and that Coolant port and the bubbles are amassing out from there.

Anyone know what gasket or whatever could be leaking in this spot? It's a huge leak, all the air drains out within 10 seconds of compressing it.

 

[theonenomad]

replace the gasket!!

 

[pSimytSi]

The throttle body gasket? Or is it the ISC o-ring?