hey all,

My standard fj20 (supra cooler and exhaust) running 13psi, well it goes to 13, then settles back around 10, is giving me the ****s.
It will get up to about 4000rpm, boosting smoothly, then it just breaks down and misses and stutters etc. Any ideas whats causing it?
spark plugs? fuel?

cheers,

Ty

Does it have one of the factory nissan pressure relief valves on the inlet manifold? This opening at these boost levels could be causing it.

Have you had it running fine at this amount of boost before?

Check that the waste gate hasn't got stuck by putting some vice grips on the actuator shaft and making it slide back and forth, this solved this kind of problem for me once when i was winding the boost up on a mates GT4 and it all of a sudden got the same simptoms as you

Often leaning out and spark plug-related miss fires can be confused. Check both. But if its leaning out the engine wont take much at that boost. Check your spark plug colours.

Good luck

yeah its actually running pretty rich, the tuner said as it is its good for 15psi so I dont think it would be leaning out...

It doesnt have the popoff valve on it. And it was running fine on 13psi when I got it back from the tuner.

I'll check plug colour and wastegate actuator.

cheers,

Ty

what plugs and gap are you running????

no idea mate, will check this arvo

[IMG][/IMG]

looks like its leaning out?
I couldnt check gap, my toolbox disappeared and had all my stuff in it, looks like about 1mm?

maybe just turn the boost down bit by bit til it stops doing it? It never did it on 10psi

Fuel stuff all ok? Filter etc? no blockages anywhere?

Those spark pluds need to be replaced. There's **** on them and fouling your ignition. No wonder its missing. Its a bit white to my liking.....rich sparks are black....

What heat range spark are you running?

i run a NGK BP6ES in my fj with a .75 gap on 20 psi
was breaking up with a bigger gap

give them a go

Check your dizzy cap. I had a well worn dizzy cap and the spark was breaking down in the high revs. I got a newy and it revved fine again.

well I replaced the plugs with BP6ES (thats what was in it already), I didnt gap them, but they were a bit smaller than what came out. I used half a tank in pretty quick time and she didnt miss a beat

cheers guys thanks for all the help,

Ty

Then its fair to say your ignbition system is not up to scratch.

It may be high resistance plug leads, well worn dizzy capo/rotor/both, coil going away or a combination of all of the above.

Interestingly, that plug pix shows quite black around the plug body but heat dramas around the nose.
This may be due to over advanced ignition resulting overheating of the ceramic insulator.
Might be worth making sure your spark timing is not too advanced as well.

Food for thought.

L8tr
E