Strange missfire

[nickisonfire]

Hi guys since 5 years i have the car and he always does this i change alot of thing and lately i change the ecu for a stocker one because i receive the car with a tuned ecu . The car is pretty stock i got hks full exaust with bee*r downpipe k's air filter greddy boost controller set to stock boost the exaust wheel are change for steel one , tomei fuel pressure regulator and yellow jacket coil + tomei fuel pump .... Ok so its a strange problem like i said i change alot of thing like clean the injector to a shop change fuel filter change all the vacuum hose resold the maf + clean change spark plug gap it to 0.8 the next step is to change to a stock ecu but it still there -_- ok my probleme is when the car is cold i always wait about 30sec to 1min to drive the car it missfire like **** and it almost not drivable as soin as the temps rise about you can feel like something unlock and everything fine at wot i also change the o2 sensor i hope can someone help me i will try to do a video i will post it soon
Thanks
Nic

[dustyGTR]

Small head gasket leak maybe? Can you figure out which cylinders are misfiring, unplug coilpacks or injectors one at a time while happening.

[Skym]

Check for intake airleak just behind MAF's (cracks in rubber intake piping, cracks in rubber piping under intake hose clamps). If MAF's get 2x airsources, can make engine stutter, similar to coilpack miss.

Also intake airleak before MAF's (clamp onto adaptor type of airfilters can cause this problem) can make ECU hit boost cut (fuel cut) earlier than it should, so check that as well.

The other is one of MAF's has failed and hitting fuelcut at 2500rpm.

[nickisonfire]

Ok i will tchek this but can this be intermittent??? Sorry for my english :s

[Skym]

English is ok (don't worry).

The stuttering usually happened on my car when exiting motorway (off ramp). It's a common problem, even Nissan dealership (deal with heaps of Skylines) knew about it.

[nickisonfire]

Ok a small upgrad i will try to put the video so y remove both of the piping after the maf to the turbo and one have a small hole so y repair it with some silicone and clean the maf and retight all of the clamp ... But it still there exactly when the car get working temp something unlock and its perfect

[nickisonfire]

Ha and i think i forget i recently adjust the idle to a wot go to about 1k rpm the setting at the ecu is all the way to the left ... Another thing is when i start the car the idle is good but sometime it drop to 900rpm and the car start to shake if i push the gas very slowly for example to hold 3k you can hear some missfire ... This happen too if i give him a good rev or just stop at a traffic light ... Its another trooble but maybee its the same i dont know ... And on the highway he do the same i try to put in 5 with 0 vacuum to hold about 120km\h but at a certain time you can feel the hesitation and he drop slowly some speed and he instantly unlock after a few second still will hold the same vacuum ... When he does this i can let the gas of and put some just after and the missfire is gone ... The car always does this since i got hit and i never figure out the trooble i dont know what to do

[Skym]

All ECU does is run engine rich, pull ignition timing to suit the engine running richer up until certain coolant temp, but ECU does initially ignore o2 sensor input, so ECU might not be picking up on the intake airleak until engine is warmer.

But if missing when engine runs rich, could be sparkplug heat range related or sparkplug gap related or the silicon is not working and still getting a intake airleak. But I think the intake airleak might be the cause.

But lag before accelerating (engine running lean) can be related to TPS failure or incorrectly setup TPS.