e46 325ti - no throttle response at all!

e46 325ti - no throttle response at all!

Author
Discussion

Fordo

Original Poster:

1,535 posts

223 months

Monday 22nd December 2014
quotequote all

Hi all, my 325ti has developed a very weird issue, and was wondering if anyone more knowledgeable than me could help?

As the title says - I have zero throttle response. Was out driving, everything fine, then suddenly, no throttle. Thankfully wasn't far from home, so very slowly I nursed car home under idle power.

A little context - earlier today I was investigating why id developed a 'no-heat through the vents' issue - i'd removed airbox, disconnected maf sensor (so i could get to and investigate heater control valve), and I changed and bled coolant, re-assembled everything and the heaters were fine again. Most likely was an airlock in the heater matrix or the heater valve had got stuck.

Anyway - the car then developed a peculiar issue - I thought more coincidental than connected - the car would start then die straight away. I disconnected the maf sensor, as that was the only sensor i'd dis-connected. Car would then start and operate normally. - So i assumed a dirty of faulty maf, and just coincidence than this problem occurred just after looking into a coolant issue.

Running with no maf should be fine for the short term - car just runs on a default map, and won't be as fuel efficient.

But just now on a test drive, suddenly the throttle just stopped responding. Up until this point, it had been fine. Now connecting the maf now doesn't cause car to die like before.

Most odd - I can't figure it out at all.

Anyone have any suggestions? (besides towing the car to a bmws specialist.). Typically these things happened around christmas time!


Thanks in advance for any suggestions

- Pete

TheEnd

15,370 posts

187 months

Monday 22nd December 2014
quotequote all
It's possibly the potentiometers in the throttle body.
There are two, and they need to match a ratio between them exactly. If one falls out of this range, it will start going into various limp modes.

The MAF is also used as a virtual throttle position sensor, so if it does detect the sensors not matching up, it will look at the airflow and try to figure out which one is telling the truth.

If that still doesn't work, it drop into another limp mode and you drive purely on the idle control valve instead.

Get a fault code read first just to check, but the throttle pots are replaceable, you'd need to swap the complete throttle body.

Fordo

Original Poster:

1,535 posts

223 months

Monday 22nd December 2014
quotequote all
Thanks, thats some good info!