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2007 Saturn Sky 2.4L 5M
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Discussion Starter · #1 ·
I've narrowed down my problems to what I think is a very small exhaust leak before the O2 sensors causing my car to think it's running lean. For background, I have a 30k mile 07 Saturn Sky 2.4 with an RPM turbo kit on it, and have been going back and forth with RPM to dial in my tune. I had a (not so great) installer do my turbo install, but seeing as I currently work in the automotive industry and have had to rework most of the items the installer did, I am pretty familiar with the system as a whole.

What I'm not familiar with is the quirks of the parts located between the head and the first o2 sensor, so that's why I think my unexplained problem is an exhaust leak. I want to tear into it and start inspecting gaskets, but I know some of the components are quirky, so I don't want to go further than I should to troubleshoot where the leak is located. I've already tried the following and they haven't seemed to cure my cars problems:

1. tightened down the down pipe to exhaust to crush the donut gasket better
2. removed the turbo/downpipe gasket and used copper RTV instead
3. Tuned the car to command a rich AFR so I know that there's not a true lean condition
4. listened all over the engine bay for leaks and can't hear anything.
5. checked the vacuum on my gauge, with a smoke machine, and with a propane torch to insure that I don't have a vacuum leak.

So my question is: how would you guys go about finding an exhaust leak without having to disassemble everything down to the head and remove all the coolant/oil lines from the turbo?
 

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@Engnineere : The Ecotec engines are known for cracks in the exhaust manifold, but they are normally between ports and do not result in leaks.

Have you monitored the O2 sensor to see when it is showing lean? If it shows lean under boost it seems unlikely to be a leak, since the exhaust system should be under pressure at that time due to backpressure from the turbo.
 

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Discussion Starter · #3 ·
@Engnineere : The Ecotec engines are known for cracks in the exhaust manifold, but they are normally between ports and do not result in leaks.

Have you monitored the O2 sensor to see when it is showing lean? If it shows lean under boost it seems unlikely to be a leak, since the exhaust system should be under pressure at that time due to backpressure from the turbo.
According to my data logs, the "lean" condition is during idle and engine braking when the vehicle is under vacuum. When I get into boost, the car runs beautifully. My last resort is just to disassemble the whole turbo assembly and replace all the gaskets with copper RTV in their place.

This is where the vehicle is reading lean and trying to correct the AFR from what I can tell.

116893
 

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According to my data logs, the "lean" condition is during idle and engine braking when the vehicle is under vacuum. When I get into boost, the car runs beautifully. My last resort is just to disassemble the whole turbo assembly and replace all the gaskets with copper RTV in their place.

This is where the vehicle is reading lean and trying to correct the AFR from what I can tell.
Lean at idle and good under load is definitely consistent with an exhaust leak, so the manifold may be the culprit.
 

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Discussion Starter · #5 ·
Lean at idle and good under load is definitely consistent with an exhaust leak, so the manifold may be the culprit.
Is there a way to remove the manifold without having to disconnect all the hard lines going to the turbo and drain the coolant/oil?
 

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Is there a way to remove the manifold without having to disconnect all the hard lines going to the turbo and drain the coolant/oil?
I am not familiar enough with a turbo-charged 2.4 to say, but I might be concerned about stress on the lines if the turbo lacks proper support.
Having it in front of you gives you the best view as to what is possible, and what is a good idea.

With a lot of things it is better to bite the bullet and get "it" out of the way rather than struggle to work around it.
 

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Discussion Starter · #7 · (Edited)
Well, so far here's what I've done to the system to chase down this problem:

1. Made a new copper gasket and surfaced the downpipe to eliminate the exhaust leak
2. pressure tested the exhaust and found zero leaks
3. pressure tested the intake and found zero leaks.
4. checked the evap purge solenoid (no leaks in the solenoid or the vacuum line to the manifold)
5. purchased a new OEM MAF and made sure the seal was air tight.
6. Pulled the injectors and greased the o-rings on the collars and on the injectors.
7. pulled the MAP sensor and greased that o-ring as well.
8. verified that I have -20 in/Hg of vacuum at idle.

I have noticed that when I unplug the MAF, the car actually seems to want to start up and run smoothly, and I don't get a p0171 lean code or corrections to my fuel trims. I don't have a wideband on the car yet, so I cant just do VE tuning, and it seems like Martin at RPM is hesitant to just do a MAF delete (if that is actually my problem) nad tune it with just the VE tables. I'm not sure I can upload datalog files here but I'd love for someone else to look at them and see if they can spot an issue that might point me in a good direction. I'm getting a little frustrated with no more progress made on what could possibly be causing the car to think it's running ultra lean on idle and think it's running rich under boost.

Also, without the MAF, the car idles very smooth but with the MAF the spark is constantly jumping and making the car stutter, and the whenever I come to a stop, the rpms drop to 400 making the car seem like it wants to die.

Things I'm planning on doing:
1. cutting off my exhaust completely and straight piping it (even if it sounds like crap)
2. installing a wideband o2 sensor.
3. checking the MAF connector and soldering the crimp connections

I can't believe that I'm the only person to ever have this problem on the RPM Motorsports LE5 turbo kit.......
 

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Discussion Starter · #10 · (Edited)
No it just seems like a complex issue. You say you pressure tested the exhaust? Did you run the smoke machine through the exhaust too?
I used an air blower in the exhaust pipe to pressurize the system and sprayed all the separate flanges down with soap water and looked for bubbles. Smoke machine will be my next step, although I haven't had any positive confirmation that the car is running badly because of an exhaust leak since it wants to correct up almost 40% long term fuel trims. Are these car ultra sensitive to pinhole leaks?
 

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Discussion Starter · #13 ·
If you are wanting to check the exhaust manifold, the turbo comes off. No other great way to do it.
I guess this is the time to pull some strings at work and change my turbo feed lines to AN braided hose and fittings. The hard line is nice but certainly makes install/uninstall a little more difficult, lol.
 

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Discussion Starter · #14 ·
Did you try modifying the maf table?
I think when Martin was tuning the MAF, he was taking the data-log MAF values and multiplying the current MAF table by -0.5% or something like that. I don't remember specifically, but I remember he did that one or two times and it still didn't fix how much fuel the ECU is trying to add.

I'm not familiar enough with tuning (other than what I've gleaned here and there logically) to understand exactly what MAF calibration does or how to do it myself, but I'm trying to learn as a backup.
 

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I think when Martin was tuning the MAF, he was taking the data-log MAF values and multiplying the current MAF table by -0.5% or something like that. I don't remember specifically, but I remember he did that one or two times and it still didn't fix how much fuel the ECU is trying to add.

I'm not familiar enough with tuning (other than what I've gleaned here and there logically) to understand exactly what MAF calibration does or how to do it myself, but I'm trying to learn as a backup.
MAF tuning is actually really simple. On the 2.4 (and the 2.0 may be different), You scan the LTFTs (and later the STFTs) and record their average per the MAF htz (I think its htz) value just like the MAF tables are set up (there is a lo and hi table). So you may get something like -9 at 1200 htz which means at a MAF reading of 1200htz, the ECM is subtracting 9% of the amount of fuel for the value in the 1200 htz cell.

To fix this, you would multiply the 1200 htz cell of the table by -0.09 (HP Tuners allows you to multiply a cell by a %). By setting up your scan table identical to the corresponding MAF table you can do a copy/paste adjustment in seconds. You then repeat.

Next scan may show -4 in the 1200 htz cell next time. We want close to 0 without going over so now we want to multiply by half the percent (HP Tuners has the option to paste by 1/2 %) so this time we multiply that value in the MAF table by -0.02. Save and repeat. +/- 3% is what we consider acceptable and my trims for the MAF cells at cruising speeds are at 0 to +/-0.1% on LTFTs and STFTs. In my open loop, LTFTs lock in around -4 due to my idle issues. The LNF does not enter open loop as it has a wide band O2 meqaning MAF tuning should be easier as you can check real time fuel trims at WOT. On the 2.4 I do a wide band reading vs target AFR over the high MAF table to calculate the % difference4 of the two to dial in the upper MAF.
 
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