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Can a throttle body be too big? | Idle & Driveability issues


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Hi all,

I previously ran a nissan 350z throttle body which is 70mm.

I've now switched to a donor Bosch 74mm throttle body because the nissan failed on me and this was all I have.

I am now experiencing issues with the car trying to idle as it hunts from time to time.

I've redone the tps calibration for the 74mm bosch. I've also started tuning base position and idle up tables from scratch (from cold as per manual). I still can't get a good idle and the car isn't so lively anymore on the response.

My PID seems sensible as I can see the TPS and Target tracks fairly close. Or is it not?

I've also checked for possible vacuum leaks but i think they're good. When i shut the base position to 0, the engine stalls.

70 to 74mm doesn't seem like a big jump but could this be too big for a 1.8L 4g93 mivec engine, stock cams, just with higher compression?


ECU is a FuryX. I've attached my map and some logs below.


bosch 74mm.pclx 74mm bosch(idle and driving) PC Datalog - 2021-10-26 6;49;12 pm.llgx

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