Hesitation Turned Into Misfire

[hutch2310]

hi guys

so i bought my r34 gtr a month ago and after a week noticed slight hesitation while cruising at 120ish, now a week later some days the car is sweeet pulls hard other days i can feel the hesitation. then driving back to work after lunch it was almost undrivable for a couple of minutes, could only put like five percent throttle on other wise it would completely miss and be hopping down the road ( it was like someone was giving it %100 throttle then nothing, all within a second. then after a couple of minutes it came right.

seems to do it when engine is warm

its now done this a few times but had a day in between with no problems, now a list of things ive tried

i read alot on here but couldnt find anything i thought was my problem. my ecu is only giving me code 55 which is all clear, i checked hoses for leaks , i forgot to do inlet gasket but i will try that, i cleaned afm's , chucked a new set of spark plugs at it, ngk platniums which are 1.1mm gapped,

been told it could be water in fuel tank but im not sure

any replys will be greatly appreciated

[hutch2310]

sorry it posted upside down

[niZmO_Man]

Sounds like AFM solder being bad.

Try gapping the spark plugs to 0.8mm

[Hadouken]

2 things. Afm and 02 sensor. For me it was the 02 sensor

[hutch2310]

afms were getting dirty due to the air filter seal around the outside had a chunk missing, ive already replaced the filter as soon as i seen it and cleaned the afms but yeah il gap the plugs this weekend, and il look into the O2 sensor, thanks

[Hadouken]

The way I checked my lambda sensors was by unplugging them. This is called running the car in open loop. If they are the problem then it should be running smooth with it unplugged

[hutch2310]

it only occasionaly runs bad, so should i unplug them and take it for a drive and see how it goes?

[Hadouken]

yes

[hutch2310]

tried unplugging them but still the same, in the process of resoldering the afm connections now

[Hadouken]

Hopefully that fixes it

[hutch2310]

put the afm back in, car was fine until it warmed up then did the exact same thing, but this time the ecu threw a code, 12 which is afm, so either it was afm or i damaged something in the afm and its that now aswell haha going to pull them both out recheck everything and solder if i need to then clear the ecu and try again, cars symptons were the same though so i am leaning towards a faulty afm

[Hadouken]

Are you going to keep your car stock? If not, it might be time to consider a map based ecu. Unless you fix It.

[hutch2310]

i do want to put an powerfc or something in it but i live 600kms (perth) away from any decent tuner so id have to raise a bit of money and go there for a couple of days and then somehow get around while they had it ...

anyway update: i took both afms out, resoldered the plug and sensor connections on both cleaned them and put them back in, its better now the car hasnt hopped (like a complete cut of power) for a couple of days but it still has hesitation, doesnt have the pull it used to just lacking a bit of power, the ecu is also no longer throwing the air flow meter code after they were soldered again

any suggestions at all anyone?

thanks

[hutch2310]

just discovered today that the hesitation is constant when the engine is still only just in vaccum and when you make about .1 bar of boost it starts pulling again if this helps anyone

[Hadouken]

does it idle stable?

[hutch2310]

yeah idle sweet as

[hutch2310]

just incase anyone follows this in the future the problem ended up being 2 problems at once haha

a bad solder connection on the afm caused the car to hop and cut power, dont know which connection it was just soldered up every main one,

secondly it still had hesitation after fixing the afm so bought the consult plug off ebay for 25 (highly recomend getting one) and noticed straight away the rear 02 sensors voltage was just staying at .4 or something and the other one was actually reading and bouncing around with different revs on so replaced the rear 02 sensor and problems solved.