Serious flat spot from pulling away when cold

[cmc]

Hi all

has anyone any thoughts on the cause of a serious flat spot I have when pulling away when my 2002 LC is cold?

When left overnight I get an intermittent problem whereby I start the car from cold, engage first gear then go to pull away and the car just lurches forward and won't drive forward. The rev needle plummets down and hunts between 600 rpm and 1,000 rpm on the verge of stalling and it simply won't take off. It's as if the car is trying to stall but the electronics are barely keeping it alive.

The only way cure it is to drop the gear stick in neutral, stab the accelerator hard revving it to about 3k revs and then re-select first gear and hope it’s cleared it. Sometime I need to do this a couple of times.

The cars regularly serviced so it's not any of the service parts and I've had this problem for a while (last had a full service in November). No dashboard lights showing and no other obvious symptoms other than a noisy secondary air pump on start up. Once the car is up and running there’s no other obvious problems.

Cheers

CMC

 

[andy_lang]

Do you let it warm up before driving off? or just start it and go?

 

[traumapat]

could be a dirty sticking throttle body. Improves as the dirt warms and softens due to heat and it stops sticking.

 

[seatcupramad23]

mine does feel abit lazy when cold but when up to temperature perfect , had mine check and logged everything seems A1 probably good thing to be honest. use some carb cleaner and clean TB but should let car get up to temperature before going on boost i'd say

 

[andy_lang]

Agreed, mine was 10 times better once cleaned out the throttle body. Defo a good 1st point of call - and its free to clean!
& yup I agree cupramad23, let it warm up fully before boosting! I turn it on, let it idle til it sits normal circa 700 - and dont go over 3k rpm until the oils upto 80, usually about 10 mins.

 

[cmc]

Do you let it warm up before driving off? or just start it and go?

Typically just start it up and drive off but don't go on boost or anything. Even from a slow pull away it just coughs and splutters and kangaroos until I prod the accelerator in neutral to 'clear its throat' if you know what I mean.

I’ll give the throttle body a clean at the weekend. I don't have VAGCOM so I’ll just need to be careful not to mess with the butterfly valve as I hear that it can get out of sorts if you're messing about it and don’t do a TB reset with VAGCOM.


Cheers

cmc

 

[JayB]

Mine does this, but I just idle for about 20 seconds if I have time and it seems to be better, but not great until it's done a couple of miles,. I am VERY sympathetic to a cold engine too, so I'm not tryin to accelerate at all hard or quickly, but it isn't happy.
Will try to clean the throttle body at the w/e and see what that does too.

 

[andy_lang]

Certinaly letting it sit and idle when turning on makes a massive difference alone - only like 1-2 mins depending on outside temperature and your doing your engine a big favour!
A full TB clean would be ideal - but every little bit helps, think with the ign on - pop a brick on the throttle and it may open it up to clean inside the butterfly................ not sure as I reset mine on my LG.

 

[traumapat]

Certinaly letting it sit and idle when turning on makes a massive difference alone - only like 1-2 mins depending on outside temperature and your doing your engine a big favour!
A full TB clean would be ideal - but every little bit helps, think with the ign on - pop a brick on the throttle and it may open it up to clean inside the butterfly................ not sure as I reset mine on my LG.

Your actually delaying it warming up causing more engine wear. faster you drive off quicker the oil warms and protects the engine. Just drive gently for the first 10-15 mins.

 

[andy_lang]

Really? I thought letting the revs drop a bit means warmer oil is being pumped around the engine rather than driving straight away on cold oil etc.
ie new scoobies run on the similar principle.
But always drive gently until its upto temp regardless.

 

[traumapat]

The trouble is the oil does little until its reached a certain temp, so during that time the engine is at most risk of wear and tear. Quicker you can hit that temp the less wear.

I see your point, giving the engine less work whilst its in the cold zone but it is still wearing internally, regardless of idling at 800rpm or running at 3k.

If youve an oil temp gauge give it a try, ive found the oil temp heats much quicker with gentle driving.

Main thing as you say is giving it some time prior to enjoying the car and after to allow the oil temp to stabilse.

 

[andy_lang]

Yer got oil temp gauge - so know its about 10 mins to get upto 70-80 degrees. hummm thats also a good point about it still not doing anything til properly warm. Perhaps I dont let it rest for a couple of mins, it only goes up by a few degrees idling.

So inial start warm up is personal preference
BUT wait at least 10 mins before going over 3k rpm
and then let it cool down after

haha anyone else comparing this to a woman right now!?!

 

[traumapat]

Nah... the curves on a leon last alot longer

 

[CupraRmark]

have you got a weak coilpack because now and again from cold ive had a slight jurk and then a slight missfire which lasts for seconds been told coilpacks going weak and will brake down one day so on the look for new ones myself maybe you getting a similar problem m8

 

[cmc]

have you got a weak coilpack because now and again from cold ive had a slight jurk and then a slight missfire which lasts for seconds been told coilpacks going weak and will brake down one day so on the look for new ones myself maybe you getting a similar problem m8

Possibly although I'd have thought a weak coil pack would have shown up elsewhere not just when cold. No engine management light issues either but if it's weak then maybe that's to be expected.

It's pretty frustrating and embarrassing when pulling away from cold and the car just lurches to a halt.

cmc

 

[BEOWULF]

I had this on my lcr When did u last changed ya spark plugs thsi was the problem with mine

 

[cmc]

I had this on my lcr When did u last changed ya spark plugs thsi was the problem with mine

Had a full service in November with all the plugs and filters etc changed.

 

[lee_woollett]

If it's an LC, could it not be something to do with the secondary air pump. Mines always a bit spluttery for the first 30 seconds or so because the secondary air pump casing has split, once the pump has gone off, the car is fine.

 

[cmc]

If it's an LC, could it not be something to do with the secondary air pump. Mines always a bit spluttery for the first 30 seconds or so because the secondary air pump casing has split, once the pump has gone off, the car is fine.

That could be it. The secondary air pump sounds like a dyson hoover just after your start the car from cold. I done a search and found a guide to fixing it. Looks like a pain to do though.

cmc

 

[JayB]

I cleaned my throttle out last night solo, just sprayed plenty of carb cleaner around it with the inlet pipe off and pumped the accelerator , then repeated a couple of times. seems to have worked a treat, it was nice and smooth this morning, 10 second idle and then drove off, sweet as a nut.
Do it, will cost about £4 for a can of cleaner from a Partco store.