Hesitation/misfire When First Accelerating

[bahanthich]

i have a r33 series 2 manual, it seems to hesitate a bit occasionally when i accelerate (normally, not foot to floor) from a traffic light etc, proably 8/10 times when im doing a start from slight to steep hill. when i put my foot down (clutch out around 1krpm), it seems to stutter,revs drop to about 500rpm, but the boost keeps building up and the car doesnt move for about 3 or 4 seconds. looking at the boost gauge, the needle increases violently (increasing not smoothly, eg instead of going from 0-1-2-3-4-5psi, its goes like 0-1-.5-1.2.5-2-3-2.5-3.5psi etc ) it gets to about 5psi, then suddendly the car picks up revs and takes off. Could this be a coil pack problem? as im getting misfire around 4500rpm also. I have changed spark plugs (bcp6res 0.8mm) and put in walboro fuel pump.

Car has intercooler/full exhaust/air filter and boost is set to about 8psi.

I though of regapping the plugs to .6 or .7, and putting epoxy on the coils, but is this a normal problem with faulty coils? (the starting hesitation issue), i though its a bit wierd because how it seems to happen more often when im on a hill then straight road. It also happens regardless of how much fuel is in the tank.

I plan on taking it to a mechanic if its not the coils/spark plugs, but if anyone has any ideas before i do so, that would be appreciated

Edited June 22, 2008 by bahanthich

[boostin_r33]

Maybe your timing's out! or your coils but usually when your coils go it just miss's and dosnt build boost at all! Have u recent just installed a boost controller?

[black_gtst]

mabie fuel pump? usually when coils fail will get to around 4000rpm then fail... can try wrapping some heat proof electrical tape round em but doesnt sound like them causin it

[nizmonut]

i pulled this of our car club site here in nz

So you got yourself a pretty mint skyline, it seem to run pretty well when you took it for a test drive, but sooner or later you get that distinctive d-d-d-d-ddd when you stomp on the gas when launching of the lights.

i've owned a few rb powered vehicals now and out of all the problems that have accured along this fabled path i have chosen , there is nothing worse then annoying detonation.

the number one reason for Detonation is the fuel choice , ALL skylines when made in japan were factory tuned to run on a MINIMUM of 100 RON or Octane fuel.

In new zealand unless your running aviation fuel or similar the popular pump supply is 91, 95, or 98 if your at BP.

what happens here is the ecu doesnt know its been shipped 15000 miles accross the pacific to a land of low grade fuel so it assumes its controlling the air fuel ratio containing 100 octane.

the higher the octane, the better the burn, the cleaner the burn, less effort to burn, so your engine runs cooler.

when your filling up with 91 for example the octane rating is 9 points below the average (which is huge in fuel terms) and the ecu measures air accordingling letting the injectors squirt in fuel to match, only problem now is your air fuel ratio is up a certain creek without a paddle.

hence the knock sensors detect something aint happening right and retard the timing...for the simpltons

for the knowledge seekers....the engine is burning low grade fuel leaving carbon build up in the bore and on the pistons, this reignites and creates hot spots on the piston head the ignites fuel before it is supposed to....

in turn the piston is fighting an uphill battle to compress an explosion.....this is detonation...

in order to reduce this effect the ecu can and will retard the timing... but no where near enough to run properly on 91 octane fuel.

the best solution here is to increase your radiators capacity, remove the thermostat, hard wire an electric fan to support the viscous fan. then run as higher octane that is avalible.

the cooler you can get your motor the less chance of hot spots forming in the combustion chamber...

Secondly, the other commonly occouring form of detonation in an rb motor is directly related to the coil packs.

for all you budding drifters, sliders, and skidders out there,, ever done the mean as burnout popping the rear bags, driven home. thinking all is well, to get up the next day and your liners detonating....yeah dont deny it, it happens to the best of us.....

this is due to what follows.... you cook your tyres on the spot, but while your doing that your engines gettin bugger all airflow, it gets hot to, the coils nesting in a nice little row in between the cam covers are baking at around 100 or so degrees,

the ceramic/ plastic casing surrounding them heats up as the heat sink cant keep them cool enough.

they expand slightly, then when they cool down, hairline cracks start forming in them.

thus, no longer insulating the ignition charge from the metal around them, earthing out before it reaches the pointy end of the NGK's...

you engine misfires due to lack of spark, the fuel sits in the cylinder for another turn to ignite, and of course if theres hot spots in there from when you do your next big sustained rpm launch it's going to do what has been described above.,,

dont fork out for another set of coils just yet , there is a little trick.

take your coils out of the engine, individually rap the bottom of each coil with electrical tape, or cover them in a non conductive glue or resin.

alternatley you can buy bosh coil packs and mount them on the inner gaurd and run HT leads to the spark plugs(recommended as it keep s them cooler).

--------------------

Officer"I didnt realize these things went that fast do you know what speed you we're doing?"

Driver"Sorry Officer i don't, the clock only goes up to 240kph."

.. i dont know hwy people keep posting new threads about missfires and skylines ifs all ways one of poor spark caused by breakdown of ignition module's coils etc etc wiring .

[bahanthich]

the thing i dont understand is how it does it more often when im on a hill/incline and just start accelerating, i though if its the coils, this wouldnt be relevant

[boostin_r33]

maybe coz u need to spool it alot harder than driving on a straight! is it cool when u drive it? When i use to use my car everyday there was a hill and for some reason each time I would go up it, it wold miss even if it was a warm day if its the same as u it's your coils!