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!

 

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!

 

Richy, please post the complete .xls and your .msq.

Jim

 

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?

 

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

 

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

 

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.

 

hrm, that's not good news :( I rely on the HR to keep a half decent idle with my rather large injectors :(

 

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!

 

No sweat brah.