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Thread: Cobb v3, AFR stuck on 14.7, smells very rich and runs rough

  1. #1

    Cobb v3, AFR stuck on 14.7, smells very rich and runs rough

    I have '06 WRX stock build........This is the same complaint I have and I have
    http://www.iwsti.com/forums/2290713-post1.html post from another forum from someone else. His solution was replacing the ECU.

    All I did was raise up the intake manifold to fix the fuel lines and I went from Lean AFR's to stuck AFR.
    New front Denso oxygen sensor installed tonight, No luck. Verified both engine grounds are bolted currently to the Intake manifold.

    I can tell from my multimeter that the ECU is not grounding the heater circuit as there is no voltage drop across the pins, just batt voltage on both.
    Tomorrow I will be doing a pinout check at the ECU once I get a diagram printed out at work.
    Last edited by mac1; 04-20-2017 at 11:00 PM.

  2. #2
    I wish I could help but hope some of the smart engine guys here will help so you can go to Huntington Beach.
    818S/C : Chassis #25 with 06 WRX 2.5 turbo, ABS, cruise, PS, A/C, Apple CarPlay, rear camera, power windows & locks, leather & other complexities.
    Mk3 Roadster #6228 4.6L, T45, IRS, PS, PB, ABS, Cruise, Koni's, 17" Halibrands, red w/ silver - 9K miles then sold @ Barrett-Jackson Jan 2011 (got back cash spent).

  3. #3
    Moonlight Performance
    Hindsight's Avatar
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    Wiring is always a tough thing to diagnose.

    I know you said you checked the grounds, but I would triple check it. Do you have a ground strap from the frame to the engine block? Do you have a ground wire going from the intake manifold to the frame? Both of these are needed.

    As you probably know, there is wiring that runs along the bottom of the intake manifold. Is it possible something was disconnected and not re-connected? Is your atmospheric pressure sensor connected? On the 06, this was part of the EGR system I believe.... either EGR or air pump - I forget which, and it cannot be deleted. TGVs plugged back in (if you still have them)?

    I would bet it's a bad or missing ground somewhere. Sometimes if you miss a ground, the ECU will pull it from another source causing a ground loop. You may get away with it for a while and suddenly it no longer works. I would check all grounds and if you don't have both grounds I mentioned above (especially the ground wire that goes from the intake manifold to the frame, which is not part of any harness - it's just a stand-alone wire), I would then look at the wiring diagram and note where every single ECU ground is located, then trace the wires to those ground positions to ensure they are properly grounded. Is your battery ground good? Have you done a voltage drop test across the all the different ground points on the car while you crank the starter to see how good your grounds are? That's the next thing I would do.

    Keep us posted.

  4. #4
    As the sensor to be grounded is on the intake manifold, and the ground strap is to the engine. what makes the ground from the intake to the engine other than the bolts that should have anti size on them?

  5. #5
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    Quote Originally Posted by UnhipPopano View Post
    What makes the ground from the intake to the engine other than the bolts that should have anti size on them?
    There is one wire, by itself, that goes from the intake manifold to the chassis. It has a ring terminal on each end. It's about 14 gauge or so.

  6. #6
    Senior Member STiPWRD's Avatar
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    Quote Originally Posted by Hindsight View Post
    There is one wire, by itself, that goes from the intake manifold to the chassis. It has a ring terminal on each end. It's about 14 gauge or so.
    I was curious about this too so I just reviewed the wiring FSM and my build photos and it looks like the engine harness has two ground terminals (GE-1 and GE-2) that both bolt up to the intake manifold. I couldn't find a wire connecting the intake manifold to the chassis or block. Either way, it looks like I'll be adding this ground connection.

  7. #7
    -I cannot find a ground strap from engine to frame.
    -Atmosphere is the MAP sensor on the throttle body I assume.
    -It has TGV delete along with aux air pump, all this with the COBB CEL mod tune loaded.

    Tonight I will do more checks with a better meter and add a ground wire. But my question now is, Is the throttle body supposed to be positioned a specific way?
    I mounted it with the ETC motor on top, not paying attention how I removed it. Looking at my TPS readings last night KO/EO I was getting 7% at closed and 100% at 1/2 throttle?

  8. #8
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    The Atmospheric pressure sensor is not the same thing as the MAP sensor. The Atmo sensor is needed to sense atmospheric pressure while the MAP sensor senses pressure inside that actual intake manifold. Two different things and both are needed by the ECU. The sensor is part of the air pump. Here is a write-up on it but unfortunately the pics dont' work. Some googling can turn pics up though. http://www.wrxforums.com/forums/11-s...re-sensor.html

    I don't think that is your issue, but if you found anything connected to a connector and thought it wasn't needed anymore (because honestly that's what it looks like - just a free floating thing that might be zip tied to a hose or something, but it isn't attached to anything other than an electrical connector), then that could be the issue.

    If you have no ground strap from the engine to the frame, that is your issue. Both the engine and the intake manifold need their own ground straps to the frame. The one for the engine comes in the kit from FFR and is a braided strap, very large, as is needed to carry the heavy starter current. The one for the intake manifold can be smaller.

    Here is a pic of the ground wire I have going from the intake manifold to the frame. Note that you MUST have the other larger ground strap to the block from the frame.
    Last edited by Hindsight; 04-21-2017 at 12:57 PM.

  9. #9
    Found the ground strap from starter bolt to lower chassis point, looks like he even scrapped the paint off for good connection.
    Identified the Atmo pressure sensor as the broken off deal zip tied to upper frame.

    TOnight I will unMarry the Cobb and see what I get on the AFR readings using an Innova code/data reader.
    Add a ground from intake to chassis.
    Might have to provide the AF sensor my own ground to see if it comes to life.

  10. #10

    Hot intake temps!!!!!

    In an effort to fix this fuel line from get rested on by the intake pipe



    I needed to separate the turbo coolant expansion away from resting on top off the MAF



    In the end I got back my Stoichometric AFR readings !!


    WHile tackling this with the guidance of everyone in this thread, I found that my FPR isn't really adjustable anymore, 29psi idle and turning it only gets me slight more,
    SO maybe this is why I get the usual P0171 lean codes, Not enough Fuel pressure at WOT under boost.



    THen I also found out my TPS readings are showing 100% throttle with only 50% ACCell pedal input???? MPG down much? 21-23


    BTW, Should I re-clock the TB?

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