Hi guys, got a problem with a gen 1 busa engine. The problem is that once the throttle is opened from idle, it miss fires and hangs at the same rpm just like it has hit a rev limiter. If you open the throttle incredibly slowly, the rpms will rise like normal. But opening the throttle over 10% makes it hit a rpm wall at that point.

Strange thing is, is that if you take the vac line off the map sensor (keeping the sensor electrically connected) , the engine runs perfectly, revs freely and very responsive.

Have tried swapping ignition coils around, new set of spark plugs and tried another map sensor.

So what could removing the vac line to the sensor be doing to make it run perfect?

All advice would be much appreciated

Thankd

Dave

i think ECU read wrong air quantity.
there are two map sensor, one connected on vac lines, and another on free air.
are both connectec and work fine?
double check if there is some leaking pipe on vac.

I agree, will check the atmospheric pressure sensor. All vacuum pipes have been checked

Thanks

Dave

We have tested the atmospheric sensor and seems to working. Resting at atmospheric pressure it shows approx 3.6v, applying pressure or vacuum makes the vague change by around 2v, so seems okay

What else would be worth checking? Running out of possibilities at the moment