Another Stutter Shudder Thread

[GTAAAH]

I just want to verify that theres nothing besides AFM's that can cause the car to cut out above 4000rpm (sometimes it jerks around a bit, normally just a few loud bangs and a slowing off revving b4 i quickly back off)

Car is a totally stock r32 GTR

It used to have a missfire right up top (5000+) but it was nowhere near as bad and new coil packs and plugs fixed it (which i left standard gapped at 1.0)

For a while 1 of my AFM's was messing up and causing the car to die randomly (on freeway etc) but i checked all the solders, replaced the wiring and sprayed some carby cleaner through both and the random dying problem is gone and has been replaced by this big cutting-out (dont know which i prefer, it used to rev out ok if a little slow). I was thinking it is possibly overboosting, it's noticeably a bit faster since i cleaned out the AFM's (before it cuts) BUT it wouldn't make sense that it's overboosting now as i didn't touch anything boost related so yeh

just wanted to know if theres anything else it could be before i fork out $240 on 2nd hand AFM's (i plan on getting z32's in 3-4 months which makes it more annoying)

cheers

Edited November 22, 2007 by GTAAAH

[race_snooze]

best plug gap is .8 correct me if I am wrong guys.

[QWK32]

do you have and aftermarket ecu or anything to monitor the afm load or voltage. one of them might be playing up and giving high (maxed out) readings causing the car to cut out.

if you don't have a way to check the voltage use a multimeter and get a voltage reading off the signal input wires at the ecu.

[GTAAAH]

i wasn't sure about the .8 gap actually, i had it at .8 with the previous coil packs, but as these new ones function 100% and i was pretty sure stock gap was 1.0 i thought i should stick to that,

I don't have an aftermarket ECU or one of those console things unfortunately, i checked all the wires going into the AFM but i guess the ecu isn't hard to get to.. but how should i check them? am i just checking resistance or am i turning the car on and looking for varying voltages? i suck at auto elec stuff

[QWK32]

yeah, just check for a varying voltage. they are a 0 - 5 v signal. so you know if your at 2000rpm under light throttle and light boost (1 - 2psi) and the afm signal voltage is at say 4.8v, then its probably stuffed.

Edited November 23, 2007 by QWK32

[GTAAAH]

hmm, is it possible to check this out without moving?

If not, i'm thinking: jam multimeter probes into connector up next to/touching the wires, tape probes, go for drive and get sum1 to check things out as i accelerate and look for signal in the range of (<insert signal range here>)

Does that sound right?

Also does anyone know what the wires are called or what colour they are? (i'm thinking AFM input or smtn) i'm pretty sure the workshop manual has some pretty simple diagrams of the ECU which will probably answer my question when i get home anyway, if not

Edited November 22, 2007 by GTAAAH

[QWK32]

hmm, is it possible to check this out without moving?

If not, i'm thinking: jam multimeter probes into connector up next to/touching the wires, tape probes, go for drive and get sum1 to check things out as i accelerate and look for signal in the range of (<insert signal range here>)

Does that sound right?

Also does anyone know what the wires are called or what colour they are? (i'm thinking AFM input or smtn) i'm pretty sure the workshop manual has some pretty simple diagrams of the ECU which will probably answer my question when i get home anyway, if not

yeah, at idle they should read about 1v and at 2500rpm they should be between 1.5 and 2v. but they might not start to play up till higher revs. if the multimeter probes are too big wrap some smaller wire around them and have a long bit hanging off the end and then use that as the probe.

the afm for the front turbo is pin 35 and the rear is pin 27, also they have a total signal range of 0v to 5v

hope this helps you figure out if its the afm's or not.

Edited November 22, 2007 by QWK32

[GTAAAH]

Oh true, i was expecting 2 line-ins for the AFM's, for some reason

Thanks!

i'll check this out tonight

[GTAAAH]

OK so they read weirdly so i bought some R33 GTR AFM's and installed them

I immediately noticed that the car was a lil rough down low but it smoothed as rev's increased

I took it up the highway and went through first 2nd and got to the top of 3rd without any fuel cuts, then it cut right up the top

From then on every time i hit around 5k it does the same cutting crap, not quite as violent, and seems to accelerate quite a bit faster with these AFM's

So anyone got any idea wat else i could try?

[TTT]

0.8mm gap on plugs as said before.

it's free, so just do it.

[GTAAAH]

eh ok i'll try it, weird if it fixes it though because it'd mean something in the car wasn't running to standard spec, thx

Edited November 26, 2007 by GTAAAH

[GTAAAH]

yo so i just bought the AFM's for nothing it seems >.<

The car started cutting out a while ago at cruising speed so i naturally thought "afm" so i sprayed it with carby cleaner and it stopped cutting out randomly but started cutting out up top

So i replace the AFM's with r33 gtr ones and it goes a bit quicker and doesn't cut once through the rev range, then starts cutting above 4/5k again

And after all that (and after regapping my plugs to .8) i notice this shit

infinite boosting ftl... i'm happy i was babying it now and only ever hit cut like 3 times haha, would have been nasty if i had kept trying ><

Edited January 11, 2008 by GTAAAH

[GeeTR]

...infinite boosting ftl

Booo to the fatigued boost line

[TTT]

didn't you have a boost gauge?

so you have been hitting like an air flow cut this whole time due to excess boost?

how lucky are you for not popping a motor...!

[GTAAAH]

Nah i only have the standard gauge which read just below 7 most of the time (but i know is innacurate) i was planning on a powerfc soonish so didn't bother with a gauge

I've only driven it like three times while it was cutting and only had it cut on me about 3 times (soon as it cut i went oh f**k and backed off) i did think it was cutting due to the AFM's though .. probably would have preferred that, lucky i didn't really drive the car much while it has been screwing up hehe

Edited January 11, 2008 by GTAAAH

[TTT]

well actually... it IS cutting out due to the AFM.

all the extra boost = extra air.

AFM can't cope with it and it send the message to cut power

but I know what you mean.

[QWK32]

yo so i just bought the AFM's for nothing it seems >.<

The car started cutting out a while ago at cruising speed so i naturally thought "afm" so i sprayed it with carby cleaner and it stopped cutting out randomly but started cutting out up top

So i replace the AFM's with r33 gtr ones and it goes a bit quicker and doesn't cut once through the rev range, then starts cutting above 4/5k again

And after all that (and after regapping my plugs to .8) i notice this shit

infinite boosting ftl

no wonder your car was cutting out, and you were getting weird afm readings, the afm's were maxed out. that probably means that your old afm's aren't buggered.