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R32 GTR misfire. O2 sensor readings.

gotenek

By gotenek,
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gotenek Apprentice

gotenek

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R32 GTR misfire. O2 sensor readings.

 

Hey everyone, hoping I can get some insight into this..

I've chasing this misfire since months. Engine boggs heavily when cold until coolant temp reaches 60 degrees celcius. Clears up as soon as it hits that mark.
Engine misfires heavily under high load above 4000 rpm. 10 psi boost.
Engine is bone stock. Stock ECU.

Work done so far:
-New coilpacks and harness.
-Spark plugs BCP7ES gapped to 0.8mm
-Fuel pressure and injectors ok. New fuel filter. 12.4 volts at fuel pump.
-Smoke tested- found air leak and replaced all 7 intake gaskets and all hoses underneath. Smoke tested again - no air leaks now.
-Swapped CAS. no change
-Swapped MAFs. no change.
-swapped boost solenoid. no change
-swapped coolant temp sensor. no change.
-Base and ignition timing is on point.

Now i'm looking at o2 sensor readings. They don't seem normal to me but I would just like to confirm with anyone with more diagnostic experience than me. Here is the data from ECUTalk via consult.

Idle after hitting closed loop: 0:00 - 0:25
Shy revs: 0:25 - 0:30
Idle : 0:30 - 1:00
Hold rpm 1300: 1:00

Please. I will appreciate any input.
Thanks!

Edited by gotenek
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gotenek Apprentice

gotenek

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Unplug them and see if the car drives better...

Have you tried swapping the ignition unit on the valley cover with a known working one?

I presume all parts were swapped with known working items?

Have you done a comp test?



I will try unplugging them thank you.
I converted to r34 gtr coilpacks so ignitor pack was deleted.
Yes eveything was from good running friend's car
Yes. Compresion test yielded even 160 psi on all cylinders while engine was hot.
Boroscope each cylinder. Valves and cylinders looked ok. Just a little bit of oil around the piston rings but thats understandable at 155,000 km.
gotenek Apprentice

gotenek

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Did this problem occur when you did the swap to 34 gtr coil packs?

Just stabbing in the dark but maybe that's your issue...



No unfortunately not.. its been there since a long time preventing me from driving the car
Dose Pipe Sutututu Grand Master

Dose Pipe Sutututu

Posted
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don't run them... you'll have shit fuel economy for now.. but at least the OEM ECU won't add in any funny fuel trims for both short and long term...

once you're ready, get an aftermarket ECU and feed a wideband o2 into it.

 

Sounds like you have electrical gremlins. 

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gotenek Apprentice

gotenek

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don't run them... you'll have shit fuel economy for now.. but at least the OEM ECU won't add in any funny fuel trims for both short and long term...

once you're ready, get an aftermarket ECU and feed a wideband o2 into it.

 

Sounds like you have electrical gremlins. 


Don't run what? Are you suggesting that my o2 sensors are okay?
gotenek Apprentice

gotenek

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unplug both o2, don't bother running them - downside is you'll have crappy fuel economy but that's Skyline life.

 


Oh i see i will try that as Hadouken suggested as well. I have new o2 sensors coming in 2 days. Just wanted some input on my current ones
gotenek Apprentice

gotenek

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New or used Engine coolant temp sensor swap in?

Check the wiring and the grounding and use a new one for $50 (kudos motorsport)

 


Used one from a friend's properly running car. I've checked wiring. Didnt see any voltage drop
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gotenek Apprentice

gotenek

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Put a scope on the negative of all the cylinders. #6 seems to be dropping below 5v. I'm not sure of what to derive from this. Checked resistance from signal wire to ecu for all cylinders and they are all at 0.182 ohms. Checked ground for Coilpacks. Resistance was nominal. Checked CAS signal wires (2) as well and they are a 0.145 which seems nominal.. I think

Swapped ECU from a friend's good running gtr. No change.. lol

 

Cylinder 6:

Rest of the cylinders: 

 

blind_elk Grand Master

blind_elk

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If the engine is stock, and the coils are good, then open the plug gap out to 1mm. Also, you seem to have the wrong heat range plugs - the correct heat range is a 6.

 

BTW - I've lost count of the number of times I've had to say that the O2 sensors are ignored under anything but cruise conditions. So if you are on boost, the O2 sensors play absolutely no part in how the engine runs.

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gotenek Apprentice

gotenek

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I've gapped the spark plugs again to 1.1mm recently and no change.. And yes, they are bcpR7es NGK 6282 (typo haha).  

The rpms start breaking up anything above 4000 rpm. The higher the load, the worse the misfire really.

MrStabby Grand Master

MrStabby

Posted
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On 9/2/2016 at 8:33 AM, blind_elk said:

BTW - I've lost count of the number of times I've had to say that the O2 sensors are ignored under anything but cruise conditions. So if you are on boost, the O2 sensors play absolutely no part in how the engine runs.

Yes also that's cruise when the engine is up to temperature, and OPs problem is when the engine is cold.

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