1986 Efi Skyline

[omally]

Hi all, every now and then the motor will run very rough then the next minute it will run fine. I have recently replace fuel and air filter. My hunch is one of the sensors is playing up. Has anyone got any ideas what would be causing this to happen?

[Factory 5]

1st you need to find out if its electrical, fuel, or mechanical

and does it happen when its cold started? (i.e.in the morning)

i would disconnect the battery, and then un plug the ECU, leave it for 24 hours to reset

The Airflow meter is plugged in correctly i hope!

My guess is the temp sensor is corroded or fouled (it tells the ECU the water temp, thus adjusting the fuel mixture). easy to fix/replace. but it might not be the final verdict.

My old R31 had similr problems, it all started after i played with the screw in the AFM, ran like crap after that, and i never got it right after that.

[the big JC]

check the PCV valve first of all they are prone to getting blocked up with crap if you arent sure where that is i can post a pic showing it

[Datto70]

The RB30E engine is very prone to this problem. In most cases it is the AFM (ECU throws a code 12). The 1st thing i usually do is check that the resistence across Pins 1 to 6 on the AFM is 382 +-2 Ohms. If all is good there then squirt some WD40 or similar on the connections and then reinstall the plug & the dust boot - it's amazing how much crap still gets under the dust boot. It may or may not run properly for a day or 2 as the ECU has to relearn the signals from the AFM. If the easy way doesn't work then if you can get access to a Gregory's #242 manual Pg 83 for the detailed method to test the AFM. I can scan the pages & send to you if required.

[Factory 5]

those pages would be a great help!

my mate has a similar problem... i thought it would be an AFM issue!

maybe i can help him fix it thanks to you!