Low Rpm/load Miss Fire

[mitchy_]

i've got an odd miss fire...

i've got a HR31 with an rb25, rb25 loom, powerfc and z32 afm.

over the past few days the missing has gotten worse, it happens more often in low rpm/cruising speeds (~2-3000rpm in third/fourth) but then if i drop back a gear or too and accelerate, 99% of the time its fine (might have the odd miss here or there) but it sounds like its running on 5 cylinders.

i've tried new plugs gapped to 0.8mm, still missed, so i took them out, cleaned them and gapped them to 0.6mm, still exactly the same.

after that i took out the AFM, it looked a little bit oily so i sprayed it with some wax and grease remover.

i also wrapped the coils with electrical tape, and put on a new air filter.

it seemed to get a little bit better after that, but is still there.

should i clean the AFM with something else?

i have a set of RB26 coils here i'm going to try, but being a low rpm miss i'm not too confident.

[trel]

could be your cas? you've pretty much eliminated MOST things it would be caused by.

[mitchy_]

had the injectors cleaned, flow tested and new o-rings, didn't fix it.

it only happens once the car gets warm, and it's more often now, and across most of the rev range.

if we unplug coil pack on cylinder 1, and 4 the idle doesnt seem to change, i've rotated coil packs around and it still does it..

any more idea's?

[shaunzo101]

had the injectors cleaned, flow tested and new o-rings, didn't fix it.

it only happens once the car gets warm, and it's more often now, and across most of the rev range.

if we unplug coil pack on cylinder 1, and 4 the idle doesnt seem to change, i've rotated coil packs around and it still does it..

any more idea's?

Do a compression test on all 6 cylinders and give us the results then we can help you alot more.

[J3TR33]

try swapping it with another ecu, 2 minute job,

my car was running on 4 cylinders, 1+3 were not firing, it wasn't the coil packs or injectors

i swapped it with another ecu and fixed my problems,

worth a try

[_Ryan_]

i had an rb30e breaking down underload when hot, it was a few earths, clean em up = win

[mitchy_]

Do a compression test on all 6 cylinders and give us the results then we can help you alot more.

had a compression test done last week, came up fine.

160, 160, 160, 155, 155, 165

stock ecu won't work too well, i've got a Z32 AFM and 740cc injectors

might try checking the earths...

[Jet 20]

Silicone up the bottom of the coils. the tape may not be doing the job.

[anthonycalais]

Change the spark plugs, i did this on my vl calais turbo and now it runs smooth as compared to misfiring like shit before hand

[mitchy_]

as i said, the plugs have already been changed (twice now)

i'm trying a set of splitfires, new loom, and new ignitor tomorrow..

[mitchy_]

tried new splitfires + loom + ignitor today, no difference.

unplugged coil packs, and its now cylinder 3 that is missing, so i swapped injector 1 and 3, and 1 misses..

so it seems like a dud injector..

i'm not sure how they go about cleaning/flow testing them.. but i think my injector is forked at low voltage, but seems to work fine at higher voltage (i'm guessing they just give them full voltage to check flow)

getting a set of stock injectors soonish to test.... anyone want to sell me ONE nismo 740cc side feed injector for a 25?

[shaunzo101]

Silicone up the bottom of the coils. the tape may not be doing the job.

the bottom of the coils? when i took mine out the other day the previous owner had taped up the top of the coil packs, then i taped up the other 3 that weren't taped and it doesn't miss a beat at high rpm now whereas it did before.