FJ20ET misfire / splutter under load

Started by muncher12, 03:20:23 AM / 16-Oct-14

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Good evening Everyone, this is my first post here, have been reading for years now.

I hvae an s12 Silvia with a dr30 fj20et in her, As soon as engine hits even a smidgen of boost it will backfire / misfire and smoke a bit too.

it can be free reeved to any rev. there are no boost leaks, I have checked voltage of tps and it opperates as it should, I have checked voltage at AFM and it reads full volts closed and steadly decreases as flat opens (it opens and shuts smoothly) the resistance of the coolant/water temp sensor is about  370-390 ohms ( I have no idea is this is normal ) the dizzy looks to be in great condition, using p10 primera coil and ignition. under reves the fuel pump voltage gets to 12.2 volda (not sure if this is enough?)?

I am so stumped have a beautiful s12 and cant use it for over a year now been trying.

if anyone can help at all I will be very gratefull. also I have read every post avail and no one seems to have exact same issue.
Post Merge

any one guys?


Might not get much help here. Few of us have FJs.

Can you check the resistance on the coil? Is it stock boost? Are the plugs going? Just seems ignition related to me, but there's no way I could know for sure.


Just wanted to second what JonB said:  it's gonna be a little hard to get someone to chime in specifically on the FJ.  I do agree with JonB's thought of it's ignition related.  The backfiring tells me that it probably has something to do with the timing being off, but most certainly I would lean towards some issue in the ignition.  Just my 2 cents....

I would like to know if the smoke you are seeing is black.  That would mean that when it does fire, the mixture is too rich/too much unburned fuel in the cyl.  With that said, keep in mind that even a bad AFM can mess with timing and ignition.  I think it would be something in the timing, but what's causing it I wouldn't know without further diagnosis.  I'd probably start by checking timing and spark under boost.

I want to add also that even something as stupid as spark plug gap COULD cause the symptoms you're experiencing.  I'd be 98% sure it's ignition related, but as far as finding out what the culprit is as to why it's not firing correctly, all I can say is good luck. 


Thanks guys, any suggestions on sites or an fj20et guru that might be further.




Sometimes it's altille slow, the site only covers the motor.

Maybe nico also


Check your ecu part number. You might have a NA ecu. I had a very similar issue with my ca18det and it turned out I had the wrong type of ecu. Good luck

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