EMGINE CUTS OFF WHEN MAF OR MAP IS PLUGGED IN!!!!!!
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This is a discussion on EMGINE CUTS OFF WHEN MAF OR MAP IS PLUGGED IN!!!!!! within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; I'm at my whits end. I finished building a hybrid engine. Ran great for the first 200 miles. The problem ...

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    Registered User Erdmann79's Avatar
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    EMGINE CUTS OFF WHEN MAF OR MAP IS PLUGGED IN!!!!!!

    I'm at my whits end.

    I finished building a hybrid engine. Ran great for the first 200 miles.

    The problem occured driving home when the driverside wheel unbolted itself and shredded up the front wire harness(no lines were severed but about 15 fused together). Never trust a friend to torque your luggs!

    All mechanicals were repaired; fender, wheel well, rim.

    After that the engine wouldn't start. Problem ECU was fried. got a new one.

    So now the engine idles very roughly and only when the MAF is left unplugged. as soon as its plugged in the engine dies. The MAFand MAP sensors have all been eliminated from being the problem. Used a similar wrx as a test. All wiring has been repaired. Checked and rechecked. I have replaced both cam and crank sensors with used replacements. No effect. Compression test came back with all 4 within spec of each other.

    Other noticable changes
    When running on lambda (unplugged MAF) at a rough idle the tailpipe is very rich. lots of smoke.

    Am i correct in assuming if it were a burned out injector or coilpack it would run on the MAF but with a cylinder miss. If it was the fuel pump, pump controller it would not run at all. Is this a global problem all cylinders.

    Here's a list of engine mods.
    2004 USDM 2.5L Block (stock 2004 internals)
    2002 USDM 2.0L Heads
    TGV deletes
    catless up-pipe
    Header unequal
    stock turbo
    stock injectors
    COBB AP
    2008 oil pump
    low temp thermostat

    Please help im loosing my mind.

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    Moderator Donkey's Avatar
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    So when you replaced the ECU you reflashed the ECU with the proper tune? How did you repair the wires?
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    Registered User Erdmann79's Avatar
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    Crimp and soder with weather shrinks for the wires. i'm a phone and cable man. Outdoor wiring is my job. As for the ECU i had my friends AP married to it for a few days. tried every map that i had stored on my computer that was set up for the TGVs (ie toggles and P-codes).

    That was one of my first thoughts. TGVs if no motors sends the unit into limp mode, but even still its not going to effect the fuel ratios and or ignition timing. Right?

    I'm waiting on COBB now to unmarry my AP from my old ECU, and sent it back. This problem has been keeping that car down for months. I need it back for my sanity at the very least. After it comes back i want to make a bunch of datalogs on what happens when the MAF is plugged in and the engine stalls.

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    Registered User Erdmann79's Avatar
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    Truth is i'm running out of ideas.

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    Moderator Donkey's Avatar
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    You need to be running the exact tune you had before for your mods. That might be part of the problem. Have you tried to datalog the car?
    Last edited by Donkey; 08-10-2011 at 12:18 PM.
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    Registered User Erdmann79's Avatar
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    The tune that was running on that wrx was only a 91 oct stage 1 tune from Cobb. I was 800 miles away from my first protune. Cobb and the tuner had confirmed that map would be fine until I had 1000 miles on the engine.

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    Registered User Erdmann79's Avatar
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    It's the same tune but from another AP. Same map file.

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    Moderator Donkey's Avatar
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    Maybe there is an issue with your front O2 sensor. I find it hard to believe you do not have a check engine light. Could be you forgot to hook up a couple grounds.
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    Registered User Erdmann79's Avatar
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    Very much could be a ground or an open circuit. The problem is which one or ones. It all comes back to the agent of change. Cause; tire friction ground down shielding on aprox 15 wires above the drive side wheel. (front wire harness.) effects; engine stall, ecu malfunction dead(assumed power surge from 12 volt feedback).

    Only got it to run once today after a lengthy cranking and accelerator coaxing. But I did notice something strange. My tachometer shows no rpms unless I hear a detonation. Or it might be opposite. I see the tach bounce momentarily and I hear detination.

    I'm curious to know how the tach acquires a signal to move. Is it off of a cylinder 1 spark. Or off a crank or cam sensor. I'm guessing I need to check grounds on that circuit. And leads as well. Along with the sensors themselves. And ideas how to verify those sensors? I should get my COBB AP back this week.

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    Registered User Erdmann79's Avatar
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    Heres a datalog snapshot of me trying to start my subie. I'm not sure what its doing or how to upload the complete file. Also throws no CELs.
    Attached Thumbnails Attached Thumbnails datalog082911.gif  

  12. #11
    Moderator Donkey's Avatar
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    Only thing I can think of is to start back probing the wires
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    Registered User Erdmann79's Avatar
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    BAZINGA!!!!!!, Finally your last post was the right call. After pulling hairs out for 6 months, and some help from the good people at IAG in Maryland. the error had been located. it was another set of fused injector leads which when fused lowerd the resistance on 3 of the injectors and caused them to act like 850cc injector scaling.

    Pain in my ass. so its finally running and its at around 850 miles. running as well as can be expected for a Hybrid motor with a somewhat stock tune. thanxs for your help Donkey. gonna start another thread on 2.5 hybrids, thermodynamics and dynamic advance

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