Increased Boost and still misfiring

[R31Nismoid]

9psi... 50psi... psi has nothing to do with it really.

It's the amount of air flowing at that level of psi.

With a hi-flow turbo, it'll be moving more air than the stocker.

So it is highly posible the fuel pump has run out.

I'd sort out the fuel pump first.

Or take it back to the workshop. Something smells fishy to me

[QuickR33Melb]

The car is manual. New platnum plugs ($22.00 each at trade price!). Fuel system is standard but I'm not looking at running 1 bar + at this point . I want to have it tuned for street use at around 12-14psi so I didn't think that would matter. The boys at TVE did put it on the dyno originally after the turbo was put back in but they said the plugs were on the way out and the oil needed changing so they didn't bother adjusting boost over standard. I changed the oil (mobile 1), filter and plugs the very next day. I have booked a dyno tune Thursday morning but as you all know it's much better walking in with a fair idea of whats happening so they don't spin shit and charge me a fortune when they don't have to.

I'm amazed to see such a high level of knowledge and apprieciate everybody's input. Thankyou all

[666DAN]

My problem was a simple overlooked fact that the battery was on it's way out....putting an unusual load on the electrical system. It affected the coil-pack power, fuel pump flow, and alternator load...it caused detonation, misfiring and a rough idle all at mysterious varying times.

I've got a $38 supercheap battery in until I get a decent one, and it works a treat.

I've spent many hours and amlmost a lot of money trying to find this out, try it out it's worth a go.

Dan

[rev210]

hate to say but, platinum plugs are a waste of money.

Your a silly sausage for not getting a bigger fuel pump. The factory one struggles even on the factory turbo once things are optimised.

Whether or not its the plugs (my guess it isn't)get the fuel pump or there will be a motor rebuild waiting for you shortly.

Does the noise sound like a metalic rattle? It's pinging if it is. If so get the fuel issue sorted

[Cubes]

A friend of mine's R33 hits an AFM cut with anything over 11psi. Stocker turbo.

[QuickR33Melb]

Rev210 you are a wise man. Believe me if the dyno shows a lack of fuel there will be a Mack truck fuel pump in the car the very same day. The last thing I want is to be in the WANTED section of the forum asking for an RB25DET.

The battery idea is a good one. I have the factory battery fitted and that is now having its ninth birthday this year.

I know the plugs are a rip off but I get work to pay for all repairs (tax payer dollars, sorry guys!!) so I just thought I'd get the ones suggested in the shop's spark plug book

[crooser]

Have you managed to try a borrowed AFM yet?

[sprint32]

GOOD ONE! You just remided me that I had a similar problem a year ago and sure enough it was the battery! (I'll be quiet now) Actually I think rev210 might be right. fuel pump.

[GTRgeoff]

Just to set the story straight on the fuel pump(s), they don't always hit their limit....sometimes they just start to lose pressure, or die outright as happened last week on a car I work on. The standard pump is good for the limit of the boost pressure of the stock turbo in the RB25, being safe at 14psi. Any more is an early death sentence for the turbine. Some have gotten away with more boost longer, but they are the exceptions.

It's possible that you may have already cracked pistons so keep that in mind and get a leakdown test and compression test and monitor blowby gas closely. it will show up even revving the engine after warmup. Look for smokey gas coming from the cam pipes after disconnecting them.

Clean your AFM element with some carby cleaner and just spray it through the post in the middle, after removing the AFM from the car.

I have to agree with R31Nismoid. A highflow turbo will flow more air at lower pressure, thence requiring more fuel. Disconnect your return fuel line in the engine bay and run it into a bucket, then start the car. There should be a healthy flow of fuel, not a trickle or anything else.

You can check your battery with a cheap multimeter both key off (11.? volts) and running (13.? volts) to determine system health.

I note you also have the cat back exhaust done. Get a high flow cat and at least a 3" dump ($260 delivered by Batmbl) if not a split pipe dump so it is free flowing all the way. The greatest gains are to be made in the front end of the exhaust but everyone (even me) seems to leave that to last. The constricted exhaust flow may be causing some problems as well.

Spark plugs: if you regap exotics it is a good chance you will remove some of that expensive material making them marginally effective. I have copper plugs in my track car (bugger it all of my cars even the V8 Soarer)) and find they are more reliable for power. They need a regap every 20-30 thou kays, or every time I go to the track as part of pre-race servicing. Great at $20 a set!!!

Try a lot of this yourself, hard to get it wrong if you take your time and you will appreciate your car more for it, and save a motza.

[Reedy]

I've got the same problem a misfiring at hi boost (> 11psi) but with different mods on my R33 Gtst with a full exhaust, FMIC, pod, dual port bov. I got a wolf 3d ems tuned last september with a new bosch fuel pump and NGK BCPR7ES sparks set to 0.8mm. Car was running fine at 14psi from a bleeder until march this year when two coils went one after the other, I then thought another coil had gone with misfiring. But coils were fine they had replaced the plugs with autolite App 3924 double platinum plugs but gapped them at 1.1mm I then got them to change it to 0.8mm which I thought made the car run better with not as much misfiring at hi boost (10 psi is fine but much more than that). They also cheaked the heat range of the autolite plugs and the same as the ngk 23-37 i think. I've reduced the overall trim of the ignition timing by up to 5 degrees and it did not make any difference also the battery voltage is almost alway 14 V on the handcontroller during normal usage so I think the battery is fine but havn't checkit under hi load. I reloaded the origimal wolf settings and didn't make a difference so I don't think theres anything wrong with the wolf and I starting to run out I ideas so any ideas are much appreciated.

[fatz]

check you intercooler hoses

one might be a bit loose and when you hit 9 psi it releases enough air for it to miss (to much fuel)

thats my sugestion

pete

[Black33]

how'd it go?

[croat]

I have the same problem. I put new plugs in and its fine for a while but a month or so later it starts missfiring again? How so you know if your coils are stuffed? is there somewhere you can send them?

[BigDatto]

Try a lower spark gap - .76 works for me where .80 wouldn't. I've had coil issues too, believe me you will know about that if it happens !

[riggaP]

I smell over boost protection. I had this same problem when trying to run more than 10psi. If you have a factory ecu you will need at least some sort of piggy back to get rid of it. Also, put copper plugs in.

[Black33]

do all cars have overboost protection? cos i've never had a problem with it and I have run 1 bar with std ecu

[riggaP]

series 2 might be different to series 1???

[Reedy]

"check you intercooler hoses

one might be a bit loose and when you hit 9 psi it releases enough air for it to miss (to much fuel)

thats my sugestion"

Couldn't see and obvious loose hose on the intercooler piping but thanks for the suggestion i'll get someon else to check it out also might change the gap from"Try a lower spark gap - .76 works for me where .80 wouldn't." as mine are only on 0.8.

P.S. Also pete unfortunately won't be able to make FD2 got to play rugby, hard after having such a good day at the last one.

[gtr jason]

my gtr has started to miss fire when it gets hot have changed the fuel pump coil packs ,fuel filter and spark plugs and have not solved the problem any other ideas

[WLD747]

Mate, i use to have the same problem when the car ran hot. Remove the nissan cover for your coils, cause they fry under there. :flamed: . And all should run sweet

cheers

ak

my gtr has started to miss fire when it gets hot have changed the fuel pump coil packs ,fuel filter and spark plugs and have not solved the problem any other ideas