[Diy_efi] Lumpy engine in closed loop cruise

[Dermot O'Hare]

I have 4-cylinder Lotus Esprit Turbo. ECU is a GM 1228708  using a 
speed density system.

In 5th gear,  trying to hold steady 85 mph,  3500 rpm, MAP about 
100-130 kPa,  ECU is in closed loop.  O2 cycling between 0-0.65 V. 
The engine is lumpy, like a slight hesitation. It feels like a very 
slight misfire,  press the throttle and it goes away as it richen up 
the mixture and accelerates  under power perfectly. The target A/F 
ratio in cruise is 14.7.

Are there any obvious causes of this,  over lean ?  etc...


Dermot



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