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  1. #1
    Wannabe Aero Lucas Cowell's Avatar
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    26 Jul 2012
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    2005 Saab 9-5 Arc
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    Misfire Help

    So a few months ago I ordered a stage 2 tuned ECU from Brew City Boost for my 05 ARC and was very happy with the performance increase. All I had to do was put a high flow filter in place of the stock paper one modification wise. The tune also gave me an open SID which lets you see live engine data. I started to notice that misfires were racking up as I drove the car normally and especially after I let off boost. I contacted the company and they very quickly responded and told me that I should run NGK BCP7es spark plugs instead of the Pfr6h-10 that were installed. I took there advice as the plugs were only a few dollars each and am currently running them in the car. The situation has improved, but the car will still register misfires under certain scenarios:

    1) when the transmission shifts near the red line
    2) immediate release of the accelerator when under boost
    3) if the engine is revved even slightly in park
    - these only show one or two registered misfires and are not detectable
    4) occasionally when I get on the throttle hard it will bog down and register 8-13 misfires before going back to normal

    Does anyone have any idea what could be causing this and how to fix it? The last thing the company told me was the my DIC was going bad, but it drives normally with no misfires to speak of while driving "normally". Any help and personal experience would be appreciated.

    Thanks

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  2. #2
    Richard Klein
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    02 Mar 2014
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    1999 SAAB 9-5
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    I found this in the Brew City Boost FAQs. It's for 9-3s, but maybe you'll find something useful in it:
    [FONT=Arial][FONT=Arial]Misfire Issues[/FONT][/FONT]
    [FONT=Arial][FONT=Arial]For the 2003+ 9-3SS/SC/CV misfiring under high load is a common problem for these tuned Saabs. The issues is likely due to coils. You can try gapping the spark plugs down first and it may help a bit. We shoot for 0.9-1.0mm gap on these cars.[/FONT][/FONT]
    [FONT=Arial][FONT=Arial]Also check your coils, if they are the white top coils those are more prone to this misfire. If the misfires continue after you have reduced the spark plug gaps, then you will want to look at getting some coils.[/FONT][/FONT]

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  3. #3
    Wannabe Aero Lucas Cowell's Avatar
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    Thanks for the reply, I've got an couple extra coil packs so I'll throw them in and see if there is any change. Any idea how to reduce the spark plug gaps? All of mine have a .9mm gap so I was going to try and reduce it to .8mm or so but I am unclear of a method to do so.

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    #SwedeSpeed

  4. #4
    Richard Klein
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    You can get really cheap spark plug gapping tools at the counter of most auto parts stores. You can do better, but they'll do to start. It takes some trial and error to get the gap right, but you bend the side electrode with a kind of hook that's built into most of these tools. Then you slide the tool in the gap. The part of the tool with the gap you want should just barely slide through and the next size up should not slide through. That's pretty much it.

    Here's a fairly good video on the subject: https://www.youtube.com/watch?v=qrLKXy4MsNg
    That's not the kind of tool I was thinking of when I mentioned the hook-like part; you won't find that on this tool. And I've never used a hammer to close the gap, but I see no reason not to do that, as long as you're gentle. Anyway, the concept is the same, and the tool they show in the video is probably the absolute cheapest you'll find, but it'll work.

    I like wire-type gages, like this, but you don't need to over-think the tool: Sears.com

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  5. #5
    Saab Nut 9-3 Aero's Avatar
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    22 Apr 2013
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    2009 9-3 2.0T SC Aero XWD\eLSD. eSID2
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    I guess the question is whether the number of misfires you do see, is "normal" or not. According to a statement regarding e.g. cylinder 1 misfire (P1301), is the total number of accepted misfires during 200 engine revolutions, specified in a load and engine speed-dependent matrix. And your four scenarios represent different load - and rev. conditions.

    Three things are essential to avoid a cylinder misfire: Proper fuel/air mixture, proper spark and sufficent compression. If there is an air leak in the vacuum hoses / -connections before the throttle body, the fuel mixture will change. The octane rating is important, mainly with regard to engine knocking, however may the stage 2 provider have a recommendation, or suggestion, on what rating is to go with the upgrade.

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  6. #6
    Wannabe Aero Lucas Cowell's Avatar
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    I appreciate your responses and it looks like I'll need to narrow down what the problem is. As of now I use 93 octane premium gas, but I'll try an octane booster next time I fill up to see if it makes a difference. I believe all the vacuum lines are good, but its worth checking. If that doesn't work then adjusting the spark plugs may do it.

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  7. #7
    Saab Nut 9-3 Aero's Avatar
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    I do note that your stage 2 provider recommended the BCP7es spark plugs, as decreasing the spark gap normally would be a step to take in an attempt to reduce/remove misfiring. As well did the misfire situation improve. For the "stage enthusiasts" in this area, however, is the favourite spark plugs NGK BCPR7ES-11 (spark gap 1,1mm) and decreasing gap towards 0,8mm (if so required to prevent misfires) - when 300+ hp are in question.

    So you have left a resistor (the -r-) based construction in your original plugs to a non-resistor type. I don't know if really that matters, however would a question to your company provide clarifications?

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