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Thread: Is my tune my problem? FI OBDI S52

  1. #1
    Join Date
    Sep 2016
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    Radford, VA.
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    95 M3

    Is my tune my problem? FI OBDI S52

    Just swapped a S52 into my 95 M3.

    Before it was a supercharged S50 on stock VF setup with a RKtunes chip (stock MAF and 30lb injectors)

    Swapped in the S52, kept the S50 manifold, changed to 42lb injectors, 2.62 pulley, 803 MAF, air/air intercooler, ltw flywheel. ect..

    Started and ran on the RKtune chip that was setup for the stock VF setup, idle was fine and air/fuel was ~11-12 at idle.

    Got a chip revision and swapped it in with current mods (unplugged the battery, waited). Now it starts up but air/fuel is around 9.0 at idle. Idle is stable unless I rev it any, then it tries to die . Seems to run better on the other chip. Since I swapped out so much at the same time, is there anything else that I should check or is it most likely the chip needs another revision?

    Sorry for my ignorance, still new to the FI world. Thanks in advance for answers!

  2. #2
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    Update: Found out I bought trashy injectors, most likely my problem.

  3. #3
    Join Date
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    The tune is for 42 lb injectors and 3.5 inch Bosch 803 hfm, correct?

    Could be issues with the bypass valve dumping air onto the HFM, confusing the measurement.

    Can be a bunch of issues when you do a bunch of things at once.

  4. #4
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    Correct, that is what the tune is for.

    I also upgraded the bypass valve to a metal one as well. It came with three springs and zero directions. I put the mid spring in it figuring I could swap it out with a stronger or weaker one if needed.

  5. #5
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    New fuel injectors did nothing. Still running super rich.

  6. #6
    Join Date
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    Do you have the resistor in the hfm signal wire? If using an 803 hfm, do you have the grounds bridged?

  7. #7
    Join Date
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    There is no resistor. The VF Kit came with one originally, but I removed it when I got the tune from RKTunes (he said there was no resistor needed). I did bridge the grounds after switching over to the OBD2 plug.

    I finally drove it around and it actually got better. I am getting an intermittent MAF code now. So I'm thinking that I need a new MAF sensor. The one I purchased was used, so I bought a new genuine Bosch. Hopefully this will square it away. I'll update after it's installed.

  8. #8
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    New MAF installed. No change. Check engine light comes and goes as I'm driving and is always p1215 MAF code. Sometimes at idle if I rev it, the engine light will instantly go out for a little while but always comes back. There is a very slight miss at idle. Only noticeable if I get out of the car and listen to the exhaust. Its not even enough for the rpm gauge to fluctuate at all

    I'm still using the plugs that came with my VF kit that are 1 heat range colder and gapped to whatever they gapped them at. Should I go another heat range colder or lessen the gap on the plugs do to the added boost? or will that even make a difference to my current issue.

  9. #9
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    I did not think it was injectors or HFM and don't think its plugs. I think it is a wiring or installation issue or the bypass valve is discharging onto the HFM sensor. I would check to make sure the HFM is not touching anything. I would also look for a loose hose, that might allow air for which fuel has been metered to escape. The idle valve hoses and the blower to TB hoses are possibilities.

  10. #10
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    I checked over every single hose and found two issues. 1. My bypass valve was installed backwards (Lol) and the second thing was I could see a piece of the oring sticking out where the plastic piece from the IACV connects to the intake manifold. So of course I took it out and (attempted) to fix that. It went back in fine, but it sits very loose and I don't believe it is sealing still. Is there a better made aftermarket part or solution to connecting the IACV to the intake?

    The plastic piece and oring are brand new, as I replaced it when I was changing everything else. I'm unsure of what brand it is, and possibly it is a poorly made aftermarket part. If there isn't a better solution then I will just order an OEM one.

    Also, pbonsalb, you're my new best friend. Thanks for the responses!

  11. #11
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    Try a new IAC to manifold fitting. They don't hold up great under boost. You can epoxy it in place. When I had my manifold off, I put a metal hose barb in there. It has held boost for over 10 years, up to 25 psi.

    The bypass valve will actually work installed backwards if the boost is low. The inlet is at a right angle to the nipple obviously top for the the bosch plastic valve and the discharge is on the bottom (you can stick your finger in there and push up against the internal spring. If you have a bosch, what are the last 3 digits? 102, 103, 108, 110, 114? The low number ones won't hold more than 6-8 psi. The bigger concern is that if the valve is discharging towards the hfm, it can confuse the hfm reading.

  12. #12
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    After attempting to put the manifold fitting back in, it fell out while I was driving. Had to limp it home. Going to order another one and hope it fixes it, if not, I'll epoxy one in. I believe my original setup had a Bosch bypass valve, but the one I have now is metal and has no names or markings on it.

    I'm still using the VF intake pipe, so the location of the discharge for the bypass valve hasn't changed, so I don't think that is causing any issues.

  13. #13
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    Ok so I took the manifold off and wired and epoxied a new fitting in. Put everything back together and no real change. I did notice when the car is running that the ICV hose from the intake to the ICV is sucked shut. Is this normal? When I had everything off I made sure the ICV was moving freely, but I guess the electric part of it could be bad possibly? or could I be mounting it backwards? If that even matters. Any suggestions? Thanks once again!

    IMG_1030.JPG

  14. #14
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    If you mean the icv hose is collapsing, it should not do that. Doubt that is your tuning issue but it is not right.

  15. #15
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    Took everything apart, remounted the ICV, put it all back together and now it runs terrible. Getting code p1281 (Control Unit Memory Supply), its running super super lean, and the ICV hose still collapses lol. Looks like I'll be taking it apart a third time. Won't have time till next weekend though. Still really have no idea what the problem is, but obviously it has to do with me not putting something together correctly.

    I also ordered an EVAP smoke tester. Hopefully find any vacuum leaks I might have.
    Last edited by badata1; 02-18-2017 at 03:49 PM.

  16. #16
    Join Date
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    ??? How are you getting OBD2 codes from an OBD1 car?
    Doubt that interpretation is correct. What are you using to scan it?
    -Abel

    - E36 328is ~210-220whp: Lots of Mods. RomRaider self-tune work in progress.
    - 2000 Z3: Many Mods.
    - 2003 VW Jetta TDI Manual 47-50mpg: Many Mods ~300ft/lbs tq, diesel, daily beater. Love/Hate relationship.
    - S52 Estoril M Coupe

  17. #17
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    just doing a stomp test. Maybe I shouldn't have added the P.

  18. #18
    Join Date
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    Ah ok. I believe the error "Control Unit Memory Supply" is from the tune not having its checksums recalculated after the edits. In this older DME it makes absolutely no difference.
    -Abel

    - E36 328is ~210-220whp: Lots of Mods. RomRaider self-tune work in progress.
    - 2000 Z3: Many Mods.
    - 2003 VW Jetta TDI Manual 47-50mpg: Many Mods ~300ft/lbs tq, diesel, daily beater. Love/Hate relationship.
    - S52 Estoril M Coupe

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