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Cold and Lumpy
Guys,
I know there could be many , many answers to this question BUT :) If a car is lumpy when cold but seems to have no other ill effects with a map, what would that normally be due to please? (Forged pistons so ringland not an issue) tvm r |
By lumpy do you mean it surges under light throttle in 2nd and more noticeably in 3rd when cold? It feels like you're pulsing the throttle slightly.
I've mapped the car myself and had the above issue since it got colder in the UK. My theory is something with intake avcs and excessive egr but not played around with it yet to see... |
Using a wideband/AFR gauge when cold see what your Readings are
My car was lumpy/stuttery when cold, turned out my MAF calibration was wrong (with standard airbox and cone filter) so had to self adjust until i cured it. My guess is your lean when cold and until your 02 sensor warms up its not compensating with extra fuel |
Lumpy
Originally Posted by Bazil_SW
(Post 11903121)
By lumpy do you mean it surges under light throttle in 2nd and more noticeably in 3rd when cold? It feels like you're pulsing the throttle slightly.
I've mapped the car myself and had the above issue since it got colder in the UK. My theory is something with intake avcs and excessive egr but not played around with it yet to see... Been a wee bit busy!! Lumpy = Noticeable jitters when engine cold, especially noticeable in 2nd and 3rd but present in all gears and manifest as lack of boost/oomph. Is most prevalent when cold but can happen at all times. using only Shell VPower/Tesco99 but doesn't really seem to make any difference which one of the two. Can be better after changing fuels, interestingly but problem always returns. Again, interestingly, the mapper has done my other wagon and there is a vaguely similar problem so suspecting the map needs a tweak. Doesn't seem to be terminal but very, very annoying! Thanks for the tip. Will keep searching for the answer. |
Info
Originally Posted by The Rig
(Post 11903276)
Using a wideband/AFR gauge when cold see what your Readings are
My car was lumpy/stuttery when cold, turned out my MAF calibration was wrong (with standard airbox and cone filter) so had to self adjust until i cured it. My guess is your lean when cold and until your 02 sensor warms up its not compensating with extra fuel Been a wee bit busy!! That's really good info mate, and frankly, the first possible proper solution I've ever seen for it. Certainly sounds close, although it does tend to manifest after warmed up but nowhere near as badly. I'll get that tested next time she's near a decent mapper. (As above, I've now had 2 wagons mapped by same chap and the 2nd one too has lumpy moments so possible mapping connection. Head gasket going though so can't comment fully till all repaired. Will probably use other mapper but will get him to check this.) Great gen thanks R |
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