sti v5 random missfire issue?

[zeroyon223]

Hi all,

Well my v5 type R has got a random missfire issue. Since having the car ecutek tuned a month ago, you can apply mid to full throttle at lower just off boost rpm\'s and it just misses quite harshly once, and doesn\'t do it for a while after that, it does it totally randomly. It had the maf replaced a day before remap with a new unit, and I\'ve only ever run a paper air filter. I do have a big AVO silicon one piece inlet though, and the mapper did say the o2 sensor has a mind of it\'s own on cruise, lean one minute, then just dumping fuel in- could this be the culprit? Doesn\'t throw a code or have any logged.

What is the limit of the stock maf? It\'s making 350bhp on wrc developments dyno at 1.2 bar, I have no further power making plans, as we\'re looking at trading for a GR sti end of the year.

Thanks in advance

[loner]

The o2 sensor reading is supposed to vary up and down at cruise...

If you\'ve just had it tuned, you should ring wrc developments and complain.

Out of interest, did they tune your stock computer, or have you got an aftermarket ecu?

[zeroyon223]

He said the o2 was way out, just goes crazy. Had it tuned a bit over a month ago, I will ring them, just wondering if it was a common issue after remap? Yes stock ecu, they\'re the only place in nz afaik who are licensed to tune with ecutek, and that v5/6 stock ecu can only be tuned via ecutek. It just has simple mods, syms equal headers, avo inlet pipe, vf28 at 1.2bar, downpipe and exhaust... Usual bolt ons. Otherwise I\'m really happy with the tune.

[loner]

Not normal, it should be running perfectly after a tune. I don\'t think the o2 sensor will be causing your symptoms,

because the ecu only uses it for cruising... your hesitation is happening mid to full throttle... but you could just unplug

it to test. I don\'t use mine.