2006 Mazda 3 MPS Question

  • October 26, 2010
  • Technical
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Question:
2006 Mazda 3 MPS
Forge BPV
Cobb Tuning SF Intake
CES Divorced wastegate TBE
XEDE (dual map)
The car on cold start jumps to 2000rpm while in open loop and slowly drops down to 1100rpm through a combination of open and closed loop. This takes around 30 seconds.  Some times the car can take a good 3 seconds of cranking to start. This is cold start, most obvious if I have not driven the car over the weekend.  Before I knew otherwise if I started to drive off before the rpm was at 1100rpm or lower it would almost stall.  Any assistance is much appreciated.

Answer:
The cold start high idle is a normal function of the Mazda 3 MPS. The extended cranking time on cold start also sounds normal for the Mazda 3 MPS with an XEDE when not driven for a couple of days. What is not normal, is the stuttering / almost stalling that you are experiencing. With the Cobb Tuning SF Intake that you have, this does alter the air flow meter (MAF) values substantially and therefore it is extremely important to have the tuning setup accurately for these changes. Our suspicion from your description of your car’s symptoms is that the cause could be due to the tuning at low rpm being inappropriate. You are experiencing this symptom only when cold as, once the engine gets warm, the O2 sensor is making corrections to counteract this symptom. If we are right, to correct this you need to have your vehicle tuned by someone who has a scan tool to read the serial data from the MPS. They need to analyse the Long and Short Term Fuel Trims and setup the tune the MAF MAP- (Fuelling adjustment in the XEDE) so that the Long Term and Short Term Fuel trims (in the Mazda data list) are close to zero with the bonnet closed and the engine at normal operating temperature. This should mean that the open loop corrections applied to these will likely be much closer to correct operation when cold. It is difficult to quantify this procedure more than this, as there are always variances between individual vehicles and different climatic conditions that should be allowed for by your local tuner.

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