So i swapped in an s5 motor into my s4 a while ago and just recently it started having that 3800 rpm hesitation. I cleaned and redid the grounds and im pretty sure my injectors were newish when i installed them. Any other ideas on why i would still have it?

 

add a ground wire off the brown/black wire to the pressure sensor and be sure you cleaned the ground ring terminal at the rear rotor housing under the UIM(this ring terminal is for the ECU/injector grounds).

if those aren't it then you may have low fuel pressure and or clogged fuel filter. double check the TPS, set the timing and replace your plugs/wires. general maintenance is important. lastly send the injectors off to be serviced again, not knowing if they are flowing properly will just keep you from adding it to your checklist.

 

i thought adding grounds to the pressure sensor was only for the 86 model? the plugs and wires are brand new. ill check the tps n timing when i see the car again. thanks

 

changed the tps. hesitation gone. thanks. now to fix the alignment and maybe drive it to las vegas to my new place.