Lumpy when started - HELP PLEASE !

[Felonious Crud]

Smoothes out the initial lumpiness. Which is *really* lumpy, jerky, nasty. Makes delicate, tight parking / un-parking manoeuvres less perilous and makes you look less of a t1t* if there are other people nearby.

* well, it mitigates it only to a certain extent in my case.

 

[CatmanV2]

Hmm
The 4200 is a little stiff when cold. It has a very slight mis, I think, which Felice reckons will be sorted by the new plugs.
I may well give it a try and see if I can spot any difference.

C

 

[hodroyd]

Putting the throttle to the floor is basically doing a throttle reset and you should not have to do this every time you start the car from cold..!!

 

[fcz360]

i do the same in the GTS MC also, press the throttle 4 times and it lessens the jumpyness (if thats a word) Migliore said its works and it does. bizarre.

 

[hodroyd]

Sounds like the operation of the choke settings are not quite right and being compensated by fuel being pumped in by the throttle pedal..??

 

[CatmanV2]

Sounds like the operation of the choke settings are not quite right and being compensated by fuel being pumped in by the throttle pedal..??

I can't see that as there won't be a mechanical accelerator pump, and anyway at fuel would be used in a few seconds. Happy to be corrected though.
C


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CatmanV2

 

[philw696]

Just reading this thread and sounds to me like a coolant temp sensor issue. The throttle is fly by wire so until engine running no fuel will be injected into the engine. You need to see some live data on the temp readings both air intake and coolant. Phil.

 

[hodroyd]

Yes chaps you are right, no mechanical pump, but I was thinking more of the ECU and what that was saying. If start-up performance is affected by applying throttle messages to the ECU prior to start and this improves early running performance, then the ECU is reacting to something..??

 

[davy83]

The ECU may be recalibrating its idle and full throttle readings? If it sees a reading above its recorded full throttle it will recalibrate. Why it would run smoother i am not sure. It may also reset some "learning" mode which makes it do less tinkering with the engine timing when cold? I know on the 3200 when you do a pedal pot calibration it resets the learned engine map and starts to re-learn it. It takes a while to get back to full performance (week or so), while it learns the engine again. At least I think this is what its doing!!! i may be wrong, although some of this is described in the technical description in the workshop manual, it just does not say in the manual how long the learning takes.

 

[hodroyd]

I think the learning curve is over actual use (miles), when it has a good picture of how you drive, it settles down and stops learning, that could be a day if you use the car enough. The ECU is supposed to look for an anomoly and react to it..??

 

[doodlebug]

Sounds like the operation of the choke settings are not quite right and being compensated by fuel being pumped in by the throttle pedal..??

I haven't found the choke on mine. Would be useful to know its whereabouts so that my missus has somewhere to hang her handbag.

Seriously, no fuel is 'pumped in' by the throttle when the engine is not running, unless of course your car has been converted to carbs I've tried 'pumping' the accelerator a few times this week and it definitely appears the car is less lumpy when cold. From my limited experience with a few 4200s, lumpiness is completely normal and is an ideal way of ensuring careful accelerator action until it is nice and warm.

 

[hodroyd]

See post 28 mate, I agree with you, but there are reservations as I point out. I don't really get a lumpy start in my 4200, you can tell the mixture is slightly rich until she warms up, but that's all..!!