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I have a nissan b14 with the ga15de engine. It had the stock air intake system from the throttle body outwards replaced with a cone filter and flexible tubing. I noticed that more recently, when accelerating, especially around 2 RPM, the needle and engine rev's would fluctuate about 2 units on the tachometer and I would hear the engine speeding up and slowing down accordingly.

Also, sometimes when at stop by a traffic lights and I pull off, about a second after, the rev's would drop to below 1/2 and behave as if its going to cut off, even though the pedal is depressed. It would recover on its own after about a 2 seconds.

I was told that if i wanted it to work as it should I have to revert to the stock system as the car is receiving input from the sensor that would normally be on the stock system.

Can anyone offer some advice on what to do please?

bee_z wrote:I was told that if i wanted it to work as it should I have to revert to the stock system as the car is receiving input from the sensor that would normally be on the stock system.

What sensor are you referring to? All the air intake sensors should be on the throttle body and none on the actual intake system of the GA15 so I doubt that could be the cause unless something was left unplugged. Note that I saw some GA16 with a separate Intake Temp Sensor mounted on the airbox but that is a completely different intake system than the GA15.

I am assuming the car was working properly before you installed the cone filter. If it was then most likely you may have an air leak somewhere between the throttle body and the cone filter.

I would reinstall the stock intake system just to make sure it works. If it still doesn't work then give the throttle body a full clean out including removing the idle sensor and cleaning it.

It could be a sensor problem which is located on the throttle body as ddog said on the GA engine.

When you installed the cone did you re-map the ecu??

But do as ddog requested, re-install your stock intake system and see if everything works from there...if it works fine, then the problem lays with the Cone system and/or re-mapping the ecu?!

UPDATE:
Diagnostic tests reveled oxygen sensor on exhaust manifold and fuel regulator was faulty.

Just a matter of replacing those now and will see how it goes.

Thanks for the advice so far. Will change the stuff and then if the issue still persists then, i'll replace the air intake with stock.