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Old 06-21-2007, 04:40 PM   #1
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Default I need help again!! My car driving me up nuts...

I have a very random misfire, it's pretty un-repeatable, it occurs 90% of the time during cruise, but can happen at any time.

see the attached pic from a datalog, (I can attach that if anyone wants it?)



you can see that the revs hold steady as does TPS and MAP, but where you can see the AFR fluctuate I have a miss fire, it's almost like the car doesn't fire on one cylinder. It's extremely annoying, especially now my daily commute now involves lots of steady state cruising :-(

I've got a set of Mazdaspeed Ignition leads and tried swopping them for another set with no joy (neither set are new however...) I've also tried new plugs, (NGK-R's and Iridiums) to no avail.

I'l literally at the end of my tether at the moment, long hours and a stressful drive does not make me enjoy my car!

Any and all advice is much appreciated!
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Old 06-21-2007, 04:55 PM   #2
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Just an out of left field idea.

I had the DB25 housing screwed together, my IAT wire got chaffed and was grounding out on the housing. This caused a "stutter" that was completely random.
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Old 06-21-2007, 05:05 PM   #3
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Just an out of left field idea.

I had the DB25 housing screwed together, my IAT wire got chaffed and was grounding out on the housing. This caused a "stutter" that was completely random.
that'd cause the MAT signal to look odd tho wouldn't it?

I'll check it out this weekend nonetheless!
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Old 06-21-2007, 05:11 PM   #4
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Richy, please post the complete .xls and your .msq.

Jim
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Old 06-21-2007, 06:30 PM   #5
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Attached, thanks Jim,

I tried to use some of the PnP settings to see if it was setup related, that's why my VE and ignition tables don't match!

As an aside when I tried the PnP VE table it was Waaaaay to lean, it barely ran it was that far off - which I don't get at all as it should run right even tho I have much larger injectors, the Req_fuel setting should sort it out?
Attached Files
File Type: zip Richy.zip (225.2 KB, 36 views)
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Old 06-21-2007, 06:42 PM   #6
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Right, which MSNSE version are you running and please tell me a location in seconds where it happens - exactly. Is 191.909s and 195.981s the deal?

Jim
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Old 06-22-2007, 03:44 AM   #7
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Right, which MSNSE version are you running and please tell me a location in seconds where it happens - exactly. Is 191.909s and 195.981s the deal?

Jim
029q_hr iirc it's just been replaced with a new version on MSextra.com

and yup you've got the time bang on the money
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Old 06-22-2007, 08:57 AM   #8
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I hate to break this to you but try 029t, the non-hr version. I always had hiccups and oddities here and there with the hr as well. If you still have the original injectors, you may want to swap them in for a test and drive along (no boosting obviously). Hope that helps,

Jim
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Old 06-22-2007, 08:59 AM   #9
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hey check this out http://www.rivercityroad.com/garage/jumpingtach.html intermittent ground issue common on 1.8's wich causes misfires and eventual coil failure. It is a free and easy fix that might help.
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Old 06-22-2007, 03:02 PM   #10
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Quote:
Originally Posted by Reverant View Post
I hate to break this to you but try 029t, the non-hr version. I always had hiccups and oddities here and there with the hr as well. If you still have the original injectors, you may want to swap them in for a test and drive along (no boosting obviously). Hope that helps,

Jim
hrm, that's not good news :( I rely on the HR to keep a half decent idle with my rather large injectors :(
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Old 06-22-2007, 03:03 PM   #11
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Originally Posted by magnamx-5 View Post
hey check this out http://www.rivercityroad.com/garage/jumpingtach.html intermittent ground issue common on 1.8's wich causes misfires and eventual coil failure. It is a free and easy fix that might help.
oh oh ohhhhhh Now I have the jumpy tach sometimes and I'd heard it's sorted by improving the front engine earth. However i've never really been able to find it (not looked that hard mind....) I didn't realise that this was the front earth!
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Old 06-22-2007, 10:55 PM   #12
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No sweat brah.
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