Missfire problems

jordancivic · Post by **jordancivic** » Mon Nov 12, 2007 4:25 am

Guys i need some help here.

What maybe the cause of a missfire at 6800rpm?

Plugs are showing no signs of detonation or heat issues.
Fueling a little rich but not anywhere near enough to cause this issue.
Timing changes not making any difference, tried +- 3 degrees with no difference ( keeping close eye on spark plugs ).

I cant see anything on the datalog that may explain whats happening, but i could do with an experts opinion.

The only thing noticed is that the alternator isnt working and the battery voltage is very low, but even with a fresh battery reading 12v the problem was the same. I understand that with the alternator working correctly the voltage would be over 13v but would this make a difference/ cause this issue?

Please note, vtec at 3500 and just started tuning the high cam, hence the wacky AF below 5500rpm, only made a couple of runs to try and rectify this issue. Let off immediatly after missfire.

Ideas guys, im stumped.

ps, im not saying this is a problem with s300, just looking for some help identifying the problem with the datalog.

Craig

Post by **Hondata** » Mon Nov 12, 2007 9:15 am

The datalogged battery voltage is below 10V. The battery voltage needs to be at least 13.8V - even with a freshly charged battery but no alternator you'll get misfires.

jordancivic · Post by **jordancivic** » Mon Nov 12, 2007 9:19 am

Thats what i thought, thats what i was hoping too, thanks mate.

I just thought that if it was a voltage problem then it may happen more often than just high revs/load?

I will report back when the alternator has been changed.

Craig