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Love hate relationship, help needed

Rustybuggy
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Rustybuggy Newbie

Rustybuggy

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Love hate relationship, help needed

89 R32 GTR 35k miles, has a misfire at idle that gradually gets worse as i drive the car for a long distance. Doesn't break up under load & seems to run well. I have been ripping my hair out trying to figure it out. I have given up & decided to reach out to the SAU community for any help. Below is what i have done to try and subside the infamous misfire. Thanks in advance for anyone thats willing to help me diagnose this turd.

 

Heres a list of everything i have done. Motor is stock other than exhaust, filter pods & ls2 GM coils.

New oem nissan 02's
New oem TPS
Used but cleaned & tested oem Injectors
Battery
Fuel pumps
Fuel filter
Re-sauder mafs, borrowed known working mafs
GM coil conversion. Reinstalled original coils, no change.
Borrowed ECU
checked all sensors on scanner, ecu talk & snap-on modis. Checked cylinder balance & hooked up oscilloscope. Also ran an injector balance test.
Replaced chassis/motor/battery ground cables.
Spark plugs @ 0.8 gap & 0.7 gap. Tried bcpr7eix & copper core ngk.
New temp sensor.
Sprayed non chlorinated brake cleaner everywhere looking for vac leaks.

Compression test was 150 psi across the board.

 

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https://www.sau.com.au/forums/topic/469178-love-hate-relationship-help-needed/
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89CAL Grand Master

89CAL

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Have you tried unplugging coilpacks and injectors one at a time to see if there is a problem there? Yes I know you have done the coils and injectors but perhaps there is a wiring harness issue.

Do you know what AFR's the car is running when it hits the issue?
Base timing OK?

Rustybuggy Newbie

Rustybuggy

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Base timing set at 20. Timing doesn't jump around when the misfire hits. Alpha tables are at around 95 on b1 & b2. I can shut off individual coils through MODIS & each one gives a very noticable change. Same with injectors. 

SkudR33 Proficient

SkudR33

Posted
Posted

Going out on a limb here... I had the exact same issue. Turned out I had a faulty injector. Test resistance in the injectors... look through my profile and you'll find a post I've written up on it. I had similar issues to you... car would sound like dog balls on idle and under high load I had a small misfire that I couldn't notice without looking at afr's

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