Hi, done a search and found nothing to really help.

 

New 555 injectors, Apexi, new plugs (standard gap????????) JD chip, running

0.9 bar via a boost controller I have just fitted.

 

Even when I was running standard boost it would sometimes miss fire when I first punched it, genererally it then was fine after the first two or three full throttle runs.

 

If I raise the revs gently it is often OK, it is in the bottom 2/3 of the rev range it gets upset. It is also not always there.

 

Still running cats but have free flowing single exit pipe.

 

Driven gently to medium speed its OK.

 

Dont think its boost leak as it not always there. CAr also seems to use loads of fuel, and I am used to Z's, but I can see the gauge moving.

 

Is it MAF?

Forgot to say, diagnostic gave 55.

Deffo worth trying a known good MAF Mark :)

Thanks Andy. Got one coming today I hope....Cheers

Is it with an auto transmission? Mine had what I thought was a mystery misfire under hard acceleration in the weeks prior to the box failing. Could be wrong but my feeling was that it was the clutch plates slipping and gripping that gave the sensation of a misfire.

Big power upgrades do tend to bring these auto boxes to an earlier demise.

No, manual, but thanks for the input.

 

I have reduced the plug gap to 0.9mm and this has fixed it 99% of the time. I think I will have to go through every connection etc but its almost ok.

Hi, done a search and found nothing to really help.

 

New 555 injectors, Apexi, new plugs (standard gap????????) JD chip, running

0.9 bar via a boost controller I have just fitted.

 

Even when I was running standard boost it would sometimes miss fire when I first punched it, genererally it then was fine after the first two or three full throttle runs.

 

If I raise the revs gently it is often OK, it is in the bottom 2/3 of the rev range it gets upset. It is also not always there.

 

Still running cats but have free flowing single exit pipe.

 

Driven gently to medium speed its OK.

 

Dont think its boost leak as it not always there. CAr also seems to use loads of fuel, and I am used to Z's, but I can see the gauge moving.

 

Is it MAF?

 

could also be a bad coilpack mate, had the same sort of thing on a skyline , it would cough splutter and pop on hard boost

OK, well I have used it again today and its 95% most of the time, dosnt like more than 1 bar of boost much either. Changed the MAF for an unknown one but the problem was exactly the same, not the best method but thats what I had.

 

I still have the cats in, I dont really think thats the problem, but what do you guys think? The chip is writtten for "no cats".

 

Next step is to remove the cats and see I think.??????

Can the coil packs be checked somehow, and thanks Forge.

wouldnt be the cats i doubt it...

take them coil packs out look for splits or the wiring loom and connectors.

but did you try out a working maf?

Mayby coil packs!

Can the coil packs be checked somehow, and thanks Forge.

 

you could try checking the resistance on each coilpack with a multimeter the one with the lowest resistance mite be your problem maybe someone can shed some light on that?

as i dont know what the resistances are on the Zeds

With the MAF I tried an unknown one, but I think its unlikely that they are both faulty and giving the same symptoms...

 

Also I have a new series three PTU fitted. So its not that (probably).

 

I will go through it step by step I guess...

I have a simular problem with mine. If you ease the power on gently it's fine but as soon as you floor it it splutters and backfires. Wish I knew what the problem was too.

Well when I have sorted it, and I hope I will, I will post the cure. My first step is to renew the coil pack connectors and as I am doing it the injector connectors too.

 

I have checked the timing and it was slightly advanced, but not much and it made no difference.

what plugs are you using??

 

try a colder plug as if its not the maf or coils it may be blowing the spark out at 1 bar, you could also try gapping it say to 0.7 to see if it helps and if it does then invest in a colder range plug and then gap them to the normal 1mm

 

Mike

Well, as I have just bought the plugs from DTA (I think) and as I was assured these were the ones to have when I mentioned the state of tune, cant remember the number but this forum agrees (generally) I will not be impressed if I have to change them at nearly £70.00.

 

But, you may have a point as I was also told the gap was fine as standard, 1.1mm. And dropping it to .9 helped.

 

Soooooo? Anyone else think it might need a cooler plug?

Well, as I have just bought the plugs from DTA (I think) and as I was assured these were the ones to have when I mentioned the state of tune, cant remember the number but this forum agrees (generally) I will not be impressed if I have to change them at nearly £70.00.

 

But, you may have a point as I was also told the gap was fine as standard, 1.1mm. And dropping it to .9 helped.

 

Soooooo? Anyone else think it might need a cooler plug?

 

really you should always have a grade cooler plug when boost pressure has been raised :)