G40 rough on start up...

[G40DAS]

what is a "cup spec" ecu? 

The aux air valve is quite expensive, VW only and I think they are over £60.

Thanks for air valve info, but it's the hose that's cracking. Is there a test for the air valve by the way ?Allegedly the "cup spec" ECU is an otherwise standard G40 ECU with a Jabba Chip in it, optimised for Cars used in the Polo cup. Maybe the guy that sold it to me was telling porkies, but it has got a Jabba chip in it and the rev limiter is higher than standard, and there is definitely more ignition advance in the map as it pinks like a b'stard on standard unleaded fuel and needs super unleaded to run properly. Car goes much better too.
Not sure if Polo cup entrants were supposed to mess with mapping, but this ECU definitely helps things along !
There used to be some sort of sealing sticker over the ECU joint (a seal to show if it's been tampered with)

[hayesey]

jabbasport didn't even exist when the G40 Cup Car races happened, last g40 cup season was 1993 if I remember correctly and jabbasport didn't start till 1997.  Although cup cars are even now still being used in other race series.  Just sounds like a normal ECU with a jabbasport chip in it, I hope you didn't pay extra for it because it was supposedly from a Cup Car!  I'm fairly sure the cup cars had to run stock ecus and were as you say. sealed.

Anyway, I'm not aware of any way of testing the air valve.

[DKnight]

well ym car hasnt altered at all, i havent swapped anything, but it is a fuel smell out of back, so i was talkin to pete and he said maybe its a dicky injector, that maybe leaks, so when sat it leaks and there will be fuel there so fire up and it burns all that off as it runs rough, once cleared it then runs...

it seems a good idea...

how many people have serviced their injectors, the peopel that are having the same problem?

its something i cant say i have ever even thought about...

[PeteG40]

have you also changed the chip?

[DKnight]

chip is back to stock

[PeteG40]

well ym car hasnt altered at all, i havent swapped anything, but it is a fuel smell out of back, so i was talkin to pete and he said maybe its a dicky injector, that maybe leaks, so when sat it leaks and there will be fuel there so fire up and it burns all that off as it runs rough, once cleared it then runs...

it seems a good idea...

how many people have serviced their injectors, the peopel that are having the same problem?

its something i cant say i have ever even thought about...

spaniel got new injectors i think.

hmmm

[supercharged spaniel]

i bought new injectors originaly and thought that maybe the issue was as mentioned above but put the old injectors back in to see but there was no difference whatsoever, so ruled that out...

[supercharged spaniel]

bump...more thoughts on this please...dk and me have been pondering vacuum pipes/fuel pressure regs/that vaccuum thingy from the servo...although i put new vaccuum pipes on since and noticed nothing so im thinking more that hose with the yellow on it out of the servo.


we both seem to have the same issue:
chugging
overfuelling
missing on start up especially after being left a while like overnight more noticable when cold.  goes after being revved/drove for 30 secs max.  cars drive fine! boost well and idle spot on (well mine does, cant say for dk)

i tried unplugging a lead to try and relicate the missing but it wasnt quite the same.  mine and dk's both chug around 2 k and it kind of 'rocks' the car like an american muscle car?!  sounds great but its not!
input/opinions needed please.

I seem to remember someone on club polo had the same issue too when i raised it ages and ages ago!  i think it may have been turbodaily?  someone defo had the same issue and i want to find them!

[PeteG40]

hows about the isv, possibly air leak that when gets warm seals?

[DKnight]

it has to be a direct fuel related issue as mine seriously over fuels, but like spankers says, its only for about 30seconds to a minute

if i then leave it parked up for say 3 hours, i come back and it starts right enough...

im gunna try a few things, but problem is i have a 1minute time window to test things lol

[PeteG40]

hmmmmmmmm fuel pressure reg?

[scotsjohn]

What engine speeds are you getting on start-up and idle after thermostat opens? I had some of the symptoms you're getting only idle stayed very poor when warm. I got 1300rpm dropped to 1100 after 30 secs. Ran smoothly till temp. started to climb then dropped to 850ish. After that it was as rough as a badger's arse with idle rhythmically dropping (a sort of four from five effect) and smell of fuel. The following worked for me but I'm not sure why.

Fired up and when revs made initial drop to 1100rpm I disconnected the blue sender for about thirty secs. Re- connected and revs held at 1100 even when thermostat opened. Tweeked idle adjust to a nice steady 850. No fuel smell and steady idle. It's been OK since. Fires up 1100 and idles 850. No problems elsewhere in the rev range.

The blue sender had been changed to try to cure the problem, does the ECU hold an old memory which needs removing? 

[DKnight]

i tihnk thats a different issue, if you unplug ecu for a while it will reset it

its such a strange one this, only so many bits you can change

spaniel did you use the same regulator?


also dunno if linked, but my car struggles to start, on turn over it sometimes sounds like a flat battery, turns slightly stops, turns again fires all ok

i thought it might have been the starter...

im gunna get all my tools out and check bloody everything...

[supercharged spaniel]

i think scotjohns issue is totally different too.  i havent changed the fuel pressure regulator though or the throttle body...i did try another ecu though and that didnt work either...i feel like its more likely something sticking over time or something?  like the fuel regulator but i have no idea what they look like inside?  its more noticable when its cold.  Warm mornings in the summer it would sometimes not do it?  like something is sticking from the cold or something doesnt like the cold?....i then thought lambda..and bought a new vag one of those..but no difference.  changed the blue temp sender too..but no difference....i havent changed the idle control valve either though.  i like petes suggestion of it having a leak that alters when it seals as it expands though.. but then i dont have any idling issues other than the odd occasion i feel like the car skips like a burble you can feel when idling away but the car is never effected by it? and other than that occasionally, it idles spot on as it should and smoothly.  i feel as tough the symptoms appeared after the de cat pipe was fitted but then that could be coincidence and seems unlikely as someone else has a decat and tried a standard chip without these problems...

[scotsjohn]

Agreed the ECU can reset itself but other sources of info such as the blue temp sender dont come with spot on values and adjustment may be part of the game. The only real difference
from my problems is the miss-fire/ rough running at 2k and that does sound like fueling/ air leak  probs which may be seperate( peteg40's temp air leak sounds like a good bet).

Only other thing I can think of thats not been mentioned is the knock sensor. If it's come loose could it start interfering with the timing? Critical torque setting seemingly.