Delay when blipping throttle.

[hellblazer]

Can anyone tell me why I have a slight delay in the engine revving after the throttle is blipped? If I just blip the throttle pedal very quickly the engine will almost die but then come back to its' idle speed. It's getting to be a pain because you have to take this into account when moving from a standstill but once on the move it runs fine.
I've checked the plugs and sprayed carb cleaner around most of the joints to the rubber elbow when it's running to see if it has an air leak but this didn't change the idle.
According to the rev counter it's idling at about 650.

It's a 1990 320i M20, completely standard (as far as I know) apart from a K&N panel filter.

[maxfield]

Slack throttle cable?

[Ritchie]

Its the usual M20 motronic crap. Not alot you can do about it really, just keep it in fresh plugs (correctly gapped) make sure the valve clearances are ok, air filter clean and there is no air leaks etc. You could always get a chip, that helps. The problem is when you snap the throttle open this bounces the afm and the ecu cant keep up with the fuelling. Thats what i think anyway!

[HairyScreech]

^^ thats kind of what i was thinking as mine does exactally the same.

[handpaper]

Yep, it's a case of 'They all do that, mate'. The comment above about the AFM is spot on; it's a slow method of measuring air flow and gives comparatively poor throttle response. Live with it or fit Megasquirt, which does away with the AFM

[DRIFTBOY]

My M30 is the same, you just have to get used to it and drive it accordingly.
It is a bit annoying sometimes though!

[hellblazer]

Ok guys thanks for the help but I still think there could be something wrong somewhere. DRIFTBOY, you say your M30 is the same. I had an E34 535(M30) and that was much sharper on the throttle compared to what I have now. I still reckon I've got an air leak somewhere as I think the plugs look a little too lean. Also I've just checked the rubber elbow again and the bit that goes to the ICV has smal cracks in the bend but when I spray carb cleaner there nothing happens to the idle.

[HairyScreech]

try around your injectors and your manafold to block gaskets

[Martinaston]

Pull the rubber elbow off before the throttle body and give the inside of the venturi a good old rub, not just a squirt of cleaner. open the throttle butterfly and give that a clean as well.
Then when thats done get your ear in as close as you can and have a listen for the click from the TP switch under it just as the throttle starts to open.
At a guess the throttle is not reaching its rest position when closed due to gunk in the venturi or its clicking too late as the throttle opens. (if its clicking at all)

[Sjoerd320i]

Can anyone tell me why I have a slight delay in the engine revving after the throttle is blipped? If I just blip the throttle pedal very quickly the engine will almost die but then come back to its' idle speed. It's getting to be a pain because you have to take this into account when moving from a standstill but once on the move it runs fine.
I've checked the plugs and sprayed carb cleaner around most of the joints to the rubber elbow when it's running to see if it has an air leak but this didn't change the idle.
According to the rev counter it's idling at about 650.

It's a 1990 320i M20, completely standard (as far as I know) apart from a K&N panel filter.

same problem here mate, only I have an auto so no problems with any kind of delay

[eldarvanyar]

Maybe the K&N panel filter is not helping if it it taking in warm air.

Also the car had an ecotech valve installed and the filter may need replacing.

[CHR1S1990]

i had a similar problem when i got my 320i. i found that it sorted its self out once i had given the throttle body a thorough clean out, as well as the idle control valve (using carb cleaner) although the problem did come back after a while. i now run on LPG and the throttle response is instant indicating something to do with perol fueling i would assume. having said that, i now have a 325i AFM as the LPG does not use this for fueling and on petrol the throttle response is instant - however runs a bit doggish at the top end (probably overfuelling). I would strongly reccomend cleaning out your ICV, throttle body, checking ur TPS "click" and make sure it is retaining no oil and if all fails perhaps try a spare AFM (they're all going to be pretty nackered now being quite old)