Help Solving a Splutter/Missfire

[JohnB]

I know its not a nissan but could use some help here.

Got the Celica back from Norbrake today and promptly fiitted a set of NGK BKR7E plugs gapped at 0.8 hoping to get rid of the Splutter/Missfire at 5,500 rpm and 6,500 rpm. (3SGTE)

It is strange it splutters at 5,500 if you keep your foot down it clears then happens again at 6,500 rpm. Only happens under load in neutral you can rev is clear all the way up to 7,000 rpm.

Boost shows 0.7 Bar Innovate shows 12.5 AFR.

If it was not getting fuel the AFR would show Lean. If it was blowing out spark surely it would happen from 5,500 rpm upwards and not be clean for a while.

I have noticed that when she is spluttering the Rev Counter also jumps up.

Running Dicktator in wasted spark with Individual Coil On Plugs (Brand New Coils)

Suggestions so far

1. Voltage Drop - Will check this one in the morning.
2. C.O.P's not coping with wasted spark - but then why clear between 5,500 and 6,500. (Anyone have a spare coil pack)

??? HELP PLEASE

[Enzio]

Does sound like a coil issue.
Also check your grounds - coils, ecu, engine grounds and check alternator connections.

[JohnB]

Thanks

I had Master Barry around yesterday, done some earth fixes and checks, we now suspect the alternator. Doing voltage checks the car idles at 13.1-13.3v and at 3000 rpm is still 13.1-13.3v. When she missfires the voltage drops badly sometimes it shows a reading of 12.5v and sometimes shows a error.

On my previous engine I had an alternator that would through at a massive spark at high rpm. I suspect this one may be doing the same thing.

Not sure about coils as it clears if you drive through the misses. We also had it running smooth recently

[JohnB]

Looks like it is mostly solved, need to get her tuned again but you will possibly be suprised at the cause or may help someone with similar problems.

I connected a voltage display to the alternator and noticed when the engine is cold the coils are getting >14v but once the engine is hot only 13.3v. Made a little cover for the alternator and butchered some pipes to feed air to the alternator and it is fine now. Voltage stays high in motion and heavy missfire has gone.

Hope it stays that way, will find out tomorrow when I take it for a descent run.