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Does This Sound Like A Damaged Afm?

Everlong-S13

By Everlong-S13,
in Engines & Forced Induction

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Everlong-S13 Community Regular

Everlong-S13

Posted
Posted

Hi guys,

I have a R34 GTT which was recently nistuned running 13psi on stock turbo with FMIC etc mods.

The car ran great a week after tune, then I took it for a long run up to Lancelin and noticed some pretty bad misfire in high revs.

While I was there I decided to clean the AFM gently with some rubbing alcohol. The misfire seems to have dissappeared however now the car has lost roughly half it's power on full boost past 3-4 rpm.

The turbo spools to 13psi as normal, and there is a loud intake noise however roughly half the power it should. I assume if it was a boost leak it would splutter and give out black smoke however this is not the case.

Curious to know if anyone knows if this is a typical symptom of a damaged AFM or something else like timing issue etc? Many thanks.

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FeZ25 Rising Star

FeZ25

Posted
Posted

Would take it back to where you got it tuned and let them give it the once over to make sure everything they adjusted is in check.

Also check your coil-packs. My car wouldn't like high revs under boost. Put a set of yellowjackets in there and hey presto, no misfire.

Everlong-S13 Community Regular

Everlong-S13

Posted
  • Author
Posted

Booked into workshop next month, I'm going to check the coil packs and spark plugs while I wait.

It's getting worse now, holding down accelerator on full boost - the car literally lurches backwards from lack of power, and then splutters on idle briefly.

Odium Grand Master

Odium

Posted
Posted

Yeah within a week of me going to a highflow/injectors/powerfc/etc my coil packs let go... Misfiring under boost / higher rpm... I got some Splitfires and it's been perfect ever since

Also make sure that your spark plugs are fine, could be that the tune is slightly off and they have fouled after a while?

Everlong-S13 Community Regular

Everlong-S13

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  • Author
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I sprayed it with a pump spray cleaning alcohol, didn't actually touch the components.

Anyway I have replaced the spark plugs with no difference.

I took it for a drive and it's worse. It seems to really drop power at high revs/boost in a sort of shuddering kind of way, and repeats this shuddering in "waves" as you keep your foot down.

Th3 coilovers are spitfires so I didn't think they would damage easily??

Anyone know what his may be?

MrStabby Grand Master

MrStabby

Posted
Posted

Anyway I have replaced the spark plugs with no difference.

I took it for a drive and it's worse. It seems to really drop power at high revs/boost in a sort of shuddering kind of way, and repeats this shuddering in "waves" as you keep your foot down.

Th3 coilovers are spitfires so I didn't think they would damage easily??

Anyone know what his may be?

Did you use the same plug type at the same gap? If there's more gap then you've made it harder for the coils to make the spark, and it will make any ignition related missfire worse.

What gap are you running now?

Everlong-S13 Community Regular

Everlong-S13

Posted
  • Author
Posted

Hi guys thanks for the replies.

My previous plugs had 0.9mm gap so were the new plugs.

I took out the spit fires and put in a spare set of stock coils with no difference, either it's not the coils or plugs or both sets of coils were faulty.

I will find another AFM to test, no idea if a damaged AFM produces symptoms like this.

SKY338 Rookie

SKY338

Posted
Posted

Hi Mate,

I am experiencing the same symptoms and i was also wondering if it was the AFM. Mine however doesn’t hesitate it just has a flat spot between 4000-5500rpm and then lunches fine after 5500rpm. Almost like it has no energy and then decides to go. Can R&R be caused by a faulty AFM?

GTR_NUTZ Collaborator

GTR_NUTZ

Posted
Posted

If its braking down and misfiring under boost/load at higher rpm then I'd say coil packs. If you're hearing a loud induction noise then maybe one of your FMIC pipes/hoses has popped off and leaking boost BUT still seals up when off boost. Might pay to re check and re tighten.

And when you are cleaning your AFM I'd recommend a break cleaner or carbie cleaner in a spray (and one that comes with a straw nosil.) That shit dries to nothing and doesn't leave a oily residue like some 'parts washers'

Good luck!!

Everlong-S13 Community Regular

Everlong-S13

Posted
  • Author
Posted

Hi GTR_NUTZ thanks for your reply.

It seems everyone is saying coil packs so I guess I need to go in that direction and buy either a set of new spitfires or OEM coilpacks. I guess I was naive thinking that the spitfires would never fail on me.

Pretty sure it isnt a leaking hose/pipe as I have checked thoroughly.

SKY338 I am not sure but I may try to get my hands on a spare AFM in any case to test.

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