Pretty Major Problem =\

[Strik3r]

Ok so this problem started occuring a few days ago, then went away. This morning when i left for uni it was happening for the first bit, but seemed to sort itself out as i got going, but when i came home this afternoon it was doing it all the way home.

The problem: Car majorly struggles to even accerate normally. Any attempt to accelerate results in bad missing, surging and jerking. At times I was struggling to maintain 100km/hr. At Idle the revs fluctuate majorly from a few hundred (almost stalling) to ~1500. Car actually did stall on me when i had the clutch in. Car would probably stall if i left it but i obviously try and keep it going by pumping accel. A/F guage is showing car running rich, even under incredibly light acceleration (5% throttle according to SAFC). AFR's in the 12's and 13's at idle, dropping to 10's and 9's when i try and accelerate (even under light accel). Nothing has changed about the car in the past couple of months.

other relevant car details:

Splitfire coilpacks

Iridium spark plugs, 6 heat range gapped @ 0.8

AFM was replaced with 2nd hand one about 4 months ago after the old one was playing up.

o2sensor seems to be working fine based on the sensor output on my apexi pen turbo timer. (and afaik wouldnt cause problems this severe anyway).

Car runs 8psi boost most of the time, with the occaisional fling of 12psi.

If you need to know anything else, post and ill supply info if i can.

The thingsI've come up with is:

- a possible leak in the i/c piping ? I dont know how or why this would have happened apart from hitting some bumps and jolting it loose. I took a really quick look and couldnt see anything obvious. I'll take a better look tomorrow in better light.

- afm playing up again

- something much much worse =\

help would be appreciated.

[InterCooL]

when i had a leak in my rb25det cooler piping, it still ran fine off boost. never took it past 80km/h but it was fine at that speed. its fairly easy to check with some detergent and a air compressor

[Taso84]

I'd say u've got a leak in the intercooler piping that somehow seals itself up from time to time, prob a very small leak.

[paulr33]

cooler pipe leak or busted afm

forget the a/f guage its useless and wont help to debug this problem

[Taso84]

when i had a leak in my rb25det cooler piping, it still ran fine off boost. never took it past 80km/h but it was fine at that speed. its fairly easy to check with some detergent and a air compressor

impossible for ur car to run fine with a large leak in the piping.

Basically what happens is the AFM takes a reading of the air coming in, tells the ECU. The ECU then detirmines how much fuel u need based on this reading. If the air subsequently leaks out, it never gets to the engine so u will run very rich, which will cause the engine to drown and hence stall.

[Bunta]

AFM, Cooler Piping or maybe a leaky BOV

I have had this happen twice to my car, Leaky piping was not as major as the AFM and I wasnt stalling much just crappy behavior down low, but the AFM caused all sorts of stalling and inability to start the car!

[Crans]

Could be a dead AFM so ecu is dumping heaps of fuel due to afm being out of range

Edited August 23, 2007 by Jason Crannage

[Oblivion]

i would be guess at the piping or AFM as well......the strugglings sounds alot like piping though.

[Strik3r]

yea im leaning towards piping because when i check the SAFC Sensor Chk page, the AFM volts seem about right. or at least i think they are right - 1.2ish volts at idle, 2-2.5 under light throttle, 3 when i started to push it a bit. Will go over the pipes as best as i can tomorrow morning and if i cant find anything, will take it down to slide/murnane.

[SECURITY]

sounds like a dieing fuel pump to me.

[Strik3r]

fuel pressure test was carried out a few months ago came back AOK. To add a twist, i took the car for a drive just then and it drove perfectly =\. Next time it happens, ill check AFM voltage. That should clue me in as to whether or not its the AFM or a leak... or something else

[SECURITY]

what does a fuel pressure test done a few months ago have to do with a possible dieing fuel pump today?

[Spook's_Skyline]

sup strik3r

can you graph your afm voltage?

makes it much easier to catch it misbehaving

i just had to deal with a afm playing silly buggers (when it felt like it)

was a pain in the arse and difficult to diagnose

[T04GTR]

when its playing up. unplug the airflow meter and see if there is any change. sounds like afm or the plug to it. does it backfire thru the intake?

[Strik3r]

what does a fuel pressure test done a few months ago have to do with a possible dieing fuel pump today?

nothing i guess. but if the fuel pump was dying, wouldnt the mixture be lean and not rediculously rich ? Bosch 040 pump. Been in the car for a few years. Can still here normal fuel pump noise at idle.

sup strik3r

can you graph your afm voltage?

hi spooky

not easily.. im just running a poor ol SAFC2. I can get a 30 second window, but thats about it. will try and pay more attention next time its playing up (or get the passenger to do so).

when its playing up. unplug the airflow meter and see if there is any change. sounds like afm or the plug to it. does it backfire thru the intake?

doable, although my AFM is in a cold air box, but i can open her up easily enough. Im not exactly sure what you mean by backfire through the intake.. shoot air back out the filter ? i dont think it is.. although i have no sure way of knowing. Nothing sounds abnormal except the exhaust popping and farting a bit from the extra fuel. if i end up finding the AFM at fault, i swear to god im tracking down a MAP based ECU. sick of stupid AFM's screwing up.

[QWK32]

forget the turbo timer reading, i got one, and a wide band o2 sensor and the timer a/f reading is so far off the mark its not funny. another thing to check would be to make sure your throttle on/off switch is switching. also you say you have a safc, has anyone been playing with it and accidently changed one of your afm in or out settings or type of afm it is.

[Strik3r]

nah no one would have touched it, but i will double check that. i know the turbo timer reading isnt worth much, but when all was working fine, it actually seemed to be relatively close to the mark - 14.2 - 14.9 while cruising and as soon as you start pushing it it dropped to 11.5-12 which is about spot on where the tune is. Even if it was wrong then, just the difference in what its reading now indicates a lot more fuel / richer mixtures. Will update with any info i find out tomorrow morning when i have a chance to give it a good look over.

thanks for the input so far guys !

[Strik3r]

hmm well, its been raining this morning, so havent had much of a chance to examine much, but when it did briefly stop, i went over most of the piping looking for anything loose - didnt find anything. Also took it for a drive and the car behaved perfectly =\ will monitor and update if i notice it again.

[TTT]

have a read of this..

sounds similar..

http://www.skylinesaustralia.com/forums/in...8437&hl=AFM

my solution at the end.

[The Mafia]

factory ECU at 12psi is no good.

Rich and retard