Revs drop to 0 when putting in clutch or putting in neutral only when engines warm

[Keegan Wood]

I have a 2003 Mazdaspeed Protege with a turbo. It has a HKS Blowoff-Valve and Tial Wastegate with a boost controller. For the boost gauge I tapped into the FPR line. When I’m driving and I press in the clutch to shift or put it in neutral the revs will drop to 0. This issue only happens when the engine is warm. I’ve already replaced the MAF sensor, EGR Valve, crank position sensor and the fuel pump, but I still have this issue. Also if I floor the gas pedal sometimes it will stick, I already cleaned the throttle body and it still happens. Any ideas on what this could be?

 

[Dawson159]

I have a 2003 Mazdaspeed Protege with a turbo. It has a HKS Blowoff-Valve and Tial Wastegate with a boost controller. For the boost gauge I tapped into the FPR line. When I’m driving and I press in the clutch to shift or put it in neutral the revs will drop to 0. This issue only happens when the engine is warm. I’ve already replaced the MAF sensor, EGR Valve, crank position sensor and the fuel pump, but I still have this issue. Also if I floor the gas pedal sometimes it will stick, I already cleaned the throttle body and it still happens. Any ideas on what this could be?

U might wanna try the mazda forums

 

[Mello]

Curious as to how you have your blowoff valve setup? Usually when using a MAF to measure your input load you would need to have the BOV recirculate back into the intake going back into the turbo compressor making a sealed system avoiding any "metered" air from escaping. This is only true if the MAF is before the turbo. If the MAF is after the turbo then this would not apply. Your symptons sound familar to us DSM folks that vent the BOV to atmosphere & still are using the MAF. DSM's have the MAF before the turbo. When venting to atmosphere you release some of the metered air that was measured confusing the ECU which cause thing to go rich on throttle plate close conditions & then a drop in rpm and or the stall. Just a thought & this seems to be similar to your situation.

 

[Keegan Wood]

Curious as to how you have your blowoff valve setup? Usually when using a MAF to measure your input load you would need to have the BOV recirculate back into the intake going back into the turbo compressor making a sealed system avoiding any "metered" air from escaping. This is only true if the MAF is before the turbo. If the MAF is after the turbo then this would not apply. Your symptons sound familar to us DSM folks that vent the BOV to atmosphere & still are using the MAF. DSM's have the MAF before the turbo. When venting to atmosphere you release some of the metered air that was measured confusing the ECU which cause thing to go rich on throttle plate close conditions & then a drop in rpm and or the stall. Just a thought & this seems to be similar to your situation.

Could tuning my car to adjust for the metered air possibly fix the problem.

 

[Mello]

No I don't believe you can make a correction in a tune for this. You could move the location of the sensor (MAF) so it's after the BOV which would in turn make it so it would not screw up the metered air measurements going into the motor. The measured air data for the ECU to use to calculate the proper fuel to air ratio would be correct this way. Or you could change the BOV air's bypass so it is pumbed back into the opening of the turbo's compressor housing & not letting it escape into the atmosphere. Research "recirculate" & "BOV" on this site for more info. Your other option is to change to a speed density setup if you don't want to have the BOV in a closed system setup arrangement.