Intermittent Misfiring

[Nacho]

Hi Peeps finally got my black b*tch GR started and trying to figure out why it's misfiring. Troubleshooting thus far:

- Checked error codes.....all I ever get out of that car is a constantly flashing N and never helpful

- Still misfiring after replacing old spark plugs with a brand new set

- Sounds dodge but pulled perfectly working coil packs from my other FTO and ran those in black car but still misfiring

- Replaced fuel filter with brand new one

- Replaced fuel with high octane, added octane booster and injector cleaner

Misfiring is not happening on every stroke but probably ever few seconds and not just at idle......have tried holding revs at about 4k and still misfires up there. Can definitely smell the unburnt fuel from the exhaust. Gut feel is that it's a vacuum leak somewhere. On a GR only vacuum hose I know of is attached to throttle body. Am I missing anywhere else?

Any other thoughts?

[Nacho]

Sorry forgot to add it sounds like and feel very much like when you accidently don't connect the vacuum hose to the back of the plenum on a GPX. Throttle is also slightly delayed and sluggish if that helps.

[silverGPX]

MAF

[Nacho]

MAF

Is that the black attachment top left hand side of the plenum? Or attached to the airbox?

[Daniel2019]

MAF

Is that the black attachment top left hand side of the plenum? Or attached to the airbox?

Intake pipe near the airbox.

[aza013]

Are the leads put back in the right firing order?


Piston order looking from the front of the car..

135
246

Connect your leads as below -

1-4
2-5
3-6

I think that is the right way lol.

[Nacho]

The leads are in the right order unfortunately Az. The sound definitely isn't as bad as when the firing order's wrong.

Any known FTO cases where the valves have just packed up and don't open and close anymore? Are our injectors common in getting blocked? if they only run at 50% capacity chances are they're not though.

[Daniel2019]

The leads are in the right order unfortunately Az.

Are they all definitely in properly? When we did them on the little Mazda we had the right order for the leads but it wasnt firing. Unplugged them all and plugged them back in and its fine. Guessing they werent in properly but just something to double check.

[kiz]

My first bet would be the leads. I was getting bad misfiring when my leads were shagged a few months back. If the coil bit in the leads isn't contacting correctly it sends it all up the crapper throughout different rev ranges. Mine got to the point where there was limited acceleration and it would misfire all the time.

Thought it was the plugs at first but once the new leads were on it was smooth sailing

[Nacho]

Yeah they're plugged in properly. I just put plugged them back in not long ago when I tried the other FTO's coil packs.

[kiz]

Yeah they're plugged in properly. I just put plugged them back in not long ago when I tried the other FTO's coil packs.

Did you test the leads to make sure they're working properly? Only takes one lead to not produce the right spark to cause issues

[silverGPX]

Try a diff maf sensor one off the airbox

[Nacho]

Yeah they're plugged in properly. I just put plugged them back in not long ago when I tried the other FTO's coil packs.

Did you test the leads to make sure they're working properly? Only takes one lead to not produce the right spark to cause issues

Same resistance across all leads on a multimeter. I upgraded my red FTO leads to Top Gun so even tried putting my old set of working leads in there and no change.

Try a diff maf sensor one off the airbox

Would like to try that but don't have a spare. Anyone in VIC got one I can test with?

[Bennoz]

I'd get your injectors cleaned mate. Intermittent random stutters at different rpm tend to be fuel rather than spark.

[Nacho]

Pulled out the injectors. Contemplating whether I can be bothered running a current through them to check spray pattern. I'll let you know how we go after an ultrasonic clean.

[payaya]

Hi Peeps finally got my black b*tch GR started and trying to figure out why it's misfiring. Troubleshooting thus far:

- Checked error codes.....all I ever get out of that car is a constantly flashing N and never helpful

- Still misfiring after replacing old spark plugs with a brand new set

- Sounds dodge but pulled perfectly working coil packs from my other FTO and ran those in black car but still misfiring

- Replaced fuel filter with brand new one

- Replaced fuel with high octane, added octane booster and injector cleaner

Misfiring is not happening on every stroke but probably ever few seconds and not just at idle......have tried holding revs at about 4k and still misfires up there. Can definitely smell the unburnt fuel from the exhaust. Gut feel is that it's a vacuum leak somewhere. On a GR only vacuum hose I know of is attached to throttle body. Am I missing anywhere else?

Any other thoughts?

Um how about these vacuum hoses:

Brake booster
Throttle body
Back on inlet manifold
Smaller hose under end of air intake
Breather hose on the middle section of intake
PCV hose
Larger hose between rocker covers

????

[Nacho]

Sorry final update........misfiring gone. Injector clean did the trick and she's purring smoothly now

[aza013]

.
Bennoz gets the cookie again .

[kiz]

.
Bennoz gets the cookie again .

662-the-cookie-monster-is-serous-about-his-cookies.jpg (30.85 KiB) Viewed 3507 times

[aza013]

Flol