Hi all, I was directed to this thread after seeking help on bimmerpost.
Throttle hesitation has been reported by Supra owners too. I’ve been wondering why I hadn’t seen any complaints online from z4 owners (till now).
My own unit is experiencing this intermittently. I also have an intermittent long crank start up issue, and I’m starting to suspect they are related.
From day 1, my car has had a long crank start up, around once every 2 months. Bimmerlink shows shadow codes pointing to HPFP and Low fuel pressure.
Late last year (about a year into ownership) the car started demonstrating a throttle hesitation.at first I thought it was my imagination cos it happens so momentarily, I would let off the gas, Wait. And try again, and it would be fine.
I realised it was not just my imagination when one day, I was stopped facing upwards on a slope, waiting to make a turn. I stepped on the gas and the car did not move (or roll back) but the rpms started bouncing and the engine sounded weird. I braked, waited a few seconds and Tried the gas and it was fine.
I have run a sensor log using bimmer link, and it shows that the fuel pressure fails to rise for the first 1-2 seconds that the accelerator is depressed. Then suddenly the pressure kicks in.
These are my observations:
- Hesitation occurs within about 500m of driving from start up.
- Time engine has run doesn’t seem to make a difference, as I’ve tried letting car warm up too. Still occurs.
- Not seemingly related to traction as roads always dry for my experiences.
- Power resumes after about 1-2 seconds without needing to depress the pedal much more
- Almost always occurs only once during a drive. Once, occured twice in one drive.
- Has occured twice in a single day, different drives.
- both cold or warm starts.
- both flat or on upwards inclines.
The feeling is like fuel starvation, and I wouldn’t expect rpms to bounce otherwise. I’m having to send my car back into Toyota, but previously they picked up nothing on their scan tool and it’s almost impossible to replicate it on demand. My guess is hpfp mechanical issues.. at least I hope it’s just that. A software fault would be impossible for Toyota to fix on their own. Before seeing this thread, I started to think it was a Toyota tuning issue
The throttle hesitation leaves no shadow codes when I check with bimmerlink. Only the long crank start up triggers hpfp and valvetronic threshold warnings (the latter is a new development)