Misfire above 4k rpm

reckals

New Member
My Gti-r has a misfire above 4k rpm. (Almost like its hitting the rev limiter). Its almost like the car backfires..... Anyone got any ideas? I looked for leaks in the intercooler piping and it seems ok but the front bumper would need to be removed to check all pipes
 

PobodY

Moderators
Staff member
What have you checked, could it be any of the obvious things?
Plug gaps?
HT leads (are they after-market ones)?
Coil?

At first guess, I'd suggest it's going to be plug gpas.
 

Al Mac

New Member
Just been dealing with a similar issue myself - turns out the coil lead was knackered. Most likely going to be something on the ignition side, so plugs, dizzy cap or leads (could be coil or amplifier but less likely I'd have thought....)
 

PobodY

Moderators
Staff member
I've previously had problems because my gap was too small (it was set at 0.5mm because that's how the plugs came, and I didn't check them); the spark is too weak at high revs.

More recently I was getting a missfire that turned-out to be the No. 3 lead - the end had come off the lead and was still attached to the plug, so it only mate intermitant contact and thus didn't always fire on that cylinder. Obviously that's an easy fix.
 

danr

Member
dirty maf?
hot air in engine bay?
also there is an engine limiter at ~5k if ecu isnt getting speedo reading (the dash sender can fail, dials will still go up/down as is seperate unit!) - will drop engine to 4k then reset.
 

PobodY

Moderators
Staff member
What should the gap be? going to give the car a good look over tomorrow....
What plugs are they and what other mods do you have?
I run 0.9mm which many might tell you is too big, but it works for me as I was trying to improve the fuel economy on long runs.
0.7mm is a pretty normal gap.
1.0mm (and larger) is the reserve of people with uprated ignition systems.
 

bensmith907

New Member
Im pretty new to the Gtir so dont take my word as gospel, but I had a simular problem which got worse and worse (came down the revs) Replacing the leads dizzy and plugs made it better but not fixed, then I set the timing (turns out I was running massively retarded) now it all seems fine

Oh yea and spray out the lead ends that go into the dizzy Inc the coil one to get a better connection. this made a massive difference on mine
 
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reckals

New Member
i have an aftermarkert turbo, running 1.3 bar, fmic, full mongoose, apexi airfilter,

just took out the plugs and they are bosch super 4?
 

stumo

Active Member
to sort your problem is a process of elimination.
This list isn't extensive or in any particular order...

check fault codes
check for air leaks on pipes (all pipes)
look at everything in the engine bay....has a small pipe come off anything, is an earth loose etc etc
when was the fuel filter changed?
check fuel pressure, esp at boost at time of misfire
check, plugs, rotor, cap, leads etc.... do not replace with crap copy items, only use Nissan branded
check timing

what did you do prior to the misfire that you haven't told us about?
 

PobodY

Moderators
Staff member
Super 4s? - That's an interesting choice; they last longer than "normal" copper core and/or precious metal tipped plugs, but I don't think they give as good a spark. That's because although you have four electrode tips, the spark only jumps to one at a time and the other three shield it to a certain extent. - It certainly doesn't jump through the middle of them, and it must be almost impossible to adjust the gap on them.

I'd be very interested to see what happens if you just drop four BCR8ES plugs in.
 

reckals

New Member
to sort your problem is a process of elimination.
This list isn't extensive or in any particular order...
check fault codes
check for air leaks on pipes (all pipes)
look at everything in the engine bay....has a small pipe come off anything, is an earth loose etc etc
when was the fuel filter changed?
check fuel pressure, esp at boost at time of misfire
check, plugs, rotor, cap, leads etc.... do not replace with crap copy items, only use Nissan branded
check timing

what did you do prior to the misfire that you haven't told us about?
I didnt change anything. it just started happening!

Super 4s? - That's an interesting choice; they last longer than "normal" copper core and/or precious metal tipped plugs, but I don't think they give as good a spark. That's because although you have four electrode tips, the spark only jumps to one at a time and the other three shield it to a certain extent. - It certainly doesn't jump through the middle of them, and it must be almost impossible to adjust the gap on them.

I'd be very interested to see what happens if you just drop four BCR8ES plugs in.
BCR8ES? would irdium plugs not be better suited? BCR8ES are standard i think? thanks so far for the help
 
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