Ford Fiesta ST mk7 Hesitation while accelerating between 2000-3000 rpm

[Enessenturk]

Hello, I have a mk7 Ford fiesta st with 88 thousand km. The car is having problems accelerating between 2000 rpm and - 3000 rpm, it acts as if I slowly press and release my foot on the gas. There is no fault in the fault device. I would be glad if you could help me.

 

[FlordPerformance]

You may need to replace the EGR valve and/or the purge valve. Check and clean the throttle body along with the intake accordion.

 

[Dialcaliper]

Hello, I have a mk7 Ford fiesta st with 88 thousand km. The car is having problems accelerating between 2000 rpm and - 3000 rpm, it acts as if I slowly press and release my foot on the gas. There is no fault in the fault device. I would be glad if you could help me.

Has the car always done this or is this new behavior?

One note, 2000-3000 RPM is where the turbocharger starts spooling up, and there can be some noticable turbo lag, especially putting the foot to floor 2000-2500 RPM. You’ll feel this as if the engine is struggling to spin up and breathe. The engine doesn’t “wake up” so to speak until above 3K RPM. There is a big surge of torque peaking at ~3500, and the engine will pull to 5500 RPM before the turbo then starts running out of breath at the top end.

If this sounds familiar, it might be simply normal behavior for a turbo engine. If there’s something else, you might start looking at other things, though odds are good (but not guaranteed) that there will eventually be a trouble code logged in the ECU

Modern cars use lots of tricks and tiny turbos to reduce or eliminate the turbo-lag cars were famous for in the 90’s, but there’s no getting around the fact that turbochargers require a certain airflow through the the turbine to spin up and start ramming more air through the engine, and the engine itself is still a small displacement 1.6L mill.

In general with the FiST engine, it’s fine to cruise between 2000-3000 RPM for better fuel economy, but if you actually want to accelerate sometime before next Sunday, you should get into the habit of downshifting to put the engine RPM above 3000. On the freeway this usually means 4th gear, and at lower speeds 2nd or 3rd gear. Part of the reason this car has a nice tight ratio gearbox is that it’s best performance is in a tight band between 3000-5500 RPM.

 

[Enessenturk]

What I'm talking about is not turbo lag. It acts like you give it gas and pull away while driving at a constant speed. I changed the coils, spark plugs and injectors and it's still going on. I have no other option but to change the high pressure pump.

 

[Mega ST]

My car was doing that and also reduced power once on boost. It eventually threw a code for the exhaust cam being over retarded. I replaced the VVT actuator and problem went away. I was over 100k Miles though.