Author Topic: Help with really annoying running problems  (Read 4091 times)

Offline supercharged spaniel

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Help with really annoying running problems
« on: March 19, 2008, 10:40:49 am »
I hope you can help.  My G40 has this really annoying habit of running  rough as if on 3 cylinders on cold morning start up.  It's not for long though probably not longer than 30 seconds if you move away straight away but it seems to have other small problems that I think are related.  It idles fine but seems to have an occasional hiccup when warmed up too  as if the throttle is quite sensitive when you release the throttle when driving .  It's done the cold morning thing for ages now and since then its had, new, and vag too, lambda probe, blue temperature sensor, W5DPO's, new coil, dizzy cap, rotor arm and ignition leads. All earth leads are fine too.  I've checked the voltage across the battery and it was at a mininum 13.7 with EVERYTHING on which is fine.  I've checked the ohms on the Co pot which is set at 550 ohms, again fine.

The strange thing is the car drives pretty well, boosting really well, it's more so at slow speeds that it seems slightly sensitive.  This morning I got a whiff of petrol but that went away quickly but it always does it really i suppose.  There are no petrol leaks, all vacuum pipes are attached and secure and all plugs have been checked and wd40'ed, both fuel pumps are new vag too.

Occasionally, and its ALWAYS when the lights are on the car will stall when started cold.  Usually when I get to the bottom of the street.  It's not always though just occasionally??  It always starts straight back up and idles fine all the time.

It's proper random and i have no idea what to do now.  the car is lightly modified:
Dewedge
Decat
Full blend
Derestricted

I wouldn't say my fuel consumption is amazing either but its not horrendous.

Is it possible my timing is slightly out?  this is not something i know how to do and dont even have the equipment.... Some suggestions please...

HELP cos it's getting on my TITS!

Offline supercharged spaniel

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Re: Help with really annoying running problems
« Reply #1 on: March 19, 2008, 10:46:36 am »
just rang someone... possible weeping injector?  when i think about it its always after a long period of waiting i.e.  over night.  maybe its flooding the cylinder over night and until its burnt away its runs dodgy?  i reckon its this!!  wha do people think??

gonna put my old ones in tonight to check
« Last Edit: March 19, 2008, 11:00:49 am by supercharged spaniel »

Offline hayesey

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Re: Re: Help with really annoying running problems
« Reply #2 on: March 19, 2008, 02:13:34 pm »
it's a possibility.  Is it using water at all?  When I had my GT was like that when first started in the morning when the HG was on it's way out as some water would leak into a bore and make it misfire till the water had gone.

Also, is your alternator healthy?  What's the voltage across the battery terminals on first cold startup with all the lights etc... on?  If it drops below about 12.7volts then the ECU will get the hump.

Offline supercharged spaniel

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Re: Re: Re: Help with really annoying running problems
« Reply #3 on: March 19, 2008, 07:24:41 pm »
cheers paul..  im not loosing any water and the corners of the head gasket show no sign of leaking at all!

ive changed the injectors for the old ones.  my new ones were aftermarket ones i bought from steve at psd but theyve done 30k now whih is not great but things can break anytime, thats life. its a possibility they have or one has died so ill see in the morning.  the injectors are  suspect though as its always after a lengthy time standing i.e. over night so one could be weeping into the bore.  ill reply tomorrow though.  the injectors look fine but i suppose how would you tell?

i tested the battery from cold start, well, ish.  been stood a few hours at least and it was fine as mentioned above, around 13.7 volts with everything on.  if it persists ill check the voltage first thing one morning...
« Last Edit: March 19, 2008, 07:25:44 pm by supercharged spaniel »

Offline supercharged spaniel

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Re: Re: Re: Re: Help with really annoying running problems
« Reply #4 on: March 20, 2008, 09:25:50 am »
grrrr still doing it after putting old injectors in.

is it posible an alternator can still be at fault after standing over night?  i tested it after standing a few hours but it only does it after standing all night.  so if i check the voltage on first start up?  could the voltage drop after standing putting the ecu into failsafe?

i seem to remember this problem starting after i fitted the vag decat pipe.  but that could just be coincidence.  
 gonna get the timing checked me thinks but i cant see it being that as it drives fine??  can anyone explain what effects bad timing would have?   would it cause issues all the time rather than first start up?

can anyone explain what issue sa dodgy alternator could cause?
« Last Edit: March 20, 2008, 09:56:52 am by supercharged spaniel »

Offline supercharged spaniel

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Re: Re: Re: Re: Re: Help with really annoying running problems
« Reply #5 on: March 20, 2008, 10:37:13 pm »
is it possible a fault code could be logged on the ecu and it clears it each morning or something?  how do the fault codes work? how does  the ecu work with faults?  i don't know?  i went to speak to someone who talked about a sensor not responding first thing as its started??

Offline Beavis

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Re: Re: Re: Re: Re: Re: Help with really annoying running problems
« Reply #6 on: March 21, 2008, 12:27:20 am »
It could be a weak alternator or battery on it's last legs. The starter motor draws a lot of amps out of the battery on initail start up combined with the lamba probe drawing current to heat the probe. After start up it could be the drain on the battery is enough that all the current is being drawn to the battery to recharge it, or that alternator has not got the oomph to run the engine management and charge the battery simultaniously. Ir may be worth connecting the multimeter to the battery when  you first start the car from stone cold in the morning to see what the voltage is then.

Offline supercharged spaniel

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Re: Re: Re: Re: Re: Re: Re: Help with really annoying running problems
« Reply #7 on: March 21, 2008, 12:31:54 am »
[quote pid=443 author=Beavis date=1206059240]It could be a weak alternator or battery on it's last legs. The starter motor draws a lot of amps out of the battery on initail start up combined with the lamba probe drawing current to heat the probe. After start up it could be the drain on the battery is enough that all the current is being drawn to the battery to recharge it, or that alternator has not got the oomph to run the engine management and charge the battery simultaniously. Ir may be worth connecting the multimeter to the battery when  you first start the car from stone cold in the morning to see what the voltage is then.[/quote]


will try that.  the battery was new in january and i have checked the voltage about 3 times and its never less than 13.7 so far, but not done first start up, but did test it after work (been standing 6 hours) and it was missing then and the voltage was above 12.7  was in the 13's.  ill test it tomorrow morning and see if its above 12.7 on start up again...  im thinking hall sender as a possibility

Offline Beavis

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Failing hall sender symptoms are usually the reverse. They are fine whist cold and degrade once heat radiates though the engine into the body of the distributer body.
« Last Edit: March 21, 2008, 12:45:52 am by Beavis »

Offline g40_kris

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wow i thought i was the only person who had all the same problems at once. Mine does exactly the same and its compleatly standard under the bonnet. Ive been told its my Co2 pot cos it stopped giving a reading. i know yours is giving a reading but have it running and unplug it see if it runs any differant. then unplug it when you last use it at night and see how it runs on cold start let me know pal

Offline supercharged spaniel

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[quote pid=559 author=g40_kris date=1206724389]wow i thought i was the only person who had all the same problems at once. Mine does exactly the same and its compleatly standard under the bonnet. Ive been told its my Co2 pot cos it stopped giving a reading. i know yours is giving a reading but have it running and unplug it see if it runs any differant. then unplug it when you last use it at night and see how it runs on cold start let me know pal[/quote]

mine seems to have settled.  i think mine is a damaged knock sensor.  im picking up a new one in the morning.  I found it didnt have any insulation on it!  i'll try your thing though if it comes back although i can get a reading on mine.  550ohms to be exact.  as it seems mine has settled since i changed the hall sender and messed about with the dodgy knock sensor cable.