High RPM misfire only at WOT

912 Views 10 Replies 6 Participants Last post by Know, 2 mo ago

Know

Discussion Starter · 3 mo ago

Hey all. I am a 2016 awd trax owner, yes I know I'm in the wrong forum but we all share the same engine..

Just wondering if anyone has experienced a high rpm misfire in their 1.4L only when WOT.. the car otherwise runs great. The misfire is heavy on cylinder 4.

Background on the car:
Zzp v3 ported, zzp diamond forged pistons, 42 lbs injectors, catless front pipe, ported intake, zzp sonic intercooler kit and zzp sonic air intake and tuned by zzp.

I've swapped injectors. New coil pack. New spark plugs gapped to .020" and misfire still takes place on cylinder 4.

Curious if anyone has run into this before? I suspect something valve train related but before I disassemble, want to see if anyone has experienced this before.

Thanks!

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Johnny B

· #2 · 3 mo ago

First thing I would check is the connectors. The connector going to the coil pack is a known issue. I would also inspect and clean all 3 connectors on the ECM.

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Reactions: 1

JLL

· #3 · 3 mo ago

Know said:
Hey all. I am a 2016 awd trax owner, yes I know I'm in the wrong forum but we all share the same engine..

Just wondering if anyone has experienced a high rpm misfire in their 1.4L only when WOT.. the car otherwise runs great. The misfire is heavy on cylinder 4.

Background on the car:
Zzp v3 ported, zzp diamond forged pistons, 42 lbs injectors, catless front pipe, ported intake, zzp sonic intercooler kit and zzp sonic air intake and tuned by zzp.

I've swapped injectors. New coil pack. New spark plugs gapped to .020" and misfire still takes place on cylinder 4.

Curious if anyone has run into this before? I suspect something valve train related but before I disassemble, want to see if anyone has experienced this before.

Thanks!

What are the fuel trims during the misfire condition?

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Reactions: 1

Know

Discussion Starter · #4 · 3 mo ago

from my hp tuners scan, at 5900 RPM my misfire counter is showing 30 misfires on cylinder 4, fuel trim is showing short term 0% long term 3.9%

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JLL

· #5 · 3 mo ago

Know said:
from my hp tuners scan, at 5900 RPM my misfire counter is showing 30 misfires on cylinder 4, fuel trim is showing short term 0% long term 3.9%

What's the #4 injector duty cycle and Spark plug look like?

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Reactions: 1

Know

Discussion Starter · #6 · 3 mo ago

it doesnt show #4 by it self on my scan, just 'injector flow rate 4.488 g/s' @ 5900 RPM WOT. Plug looked fine, but top of piston was discoloured compared to the rest.

just a reminder, the car runs perfect, this problem only happens WOT at high rpm.

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Know

Discussion Starter · #7 · 2 mo ago

Compression is 200 PSI on cylinder 4. Leakdown test @ 90 PSI holds at TDC on cylinder 4. I can see pitting on exhaust cam on cylinder 4.....

Ive swapped injectors, changed coil packs, new spark plugs, compression is 200 psi, leakdown holds 90 psi... I think the cam/rocker/lifter is failing.

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NotCruzing

· #8 · 2 mo ago

Know said:
New spark plugs gapped to .020"

Would you get more complete burn with a bigger gap?

Probably doesn't matter now given exhaust cam damage. . .

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geddinwk

· #9 · 2 mo ago

What brand plugs are you using

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jblackburn

· #10 · 2 mo ago

It sounds like you are running into valve float, esp given the visible cam damage

They do sell upgraded valve springs for these motors, and it is only usually an issue with a high-flow turbo and high RPM, both conditions you meet.

BNR Valve Springs 1.4T Cruze/Sonic-BNR-LUV-LUJ-VSPRING

store.badnewsracing.net

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Know

Discussion Starter · #11 · 2 mo ago

jblackburn said:
It sounds like you are running into valve float, esp given the visible cam damage

They do sell upgraded valve springs for these motors, and it is only usually an issue with a high-flow turbo and high RPM, both conditions you meet.

BNR Valve Springs 1.4T Cruze/Sonic-BNR-LUV-LUJ-VSPRING

store.badnewsracing.net

thanks for your input, I am planning on buying valve springs and upgraded cam. I am also changing all lifters while im there.

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