Jump to content
lectrotek

G40 rough as a badger's arse on throttle at low revs

Recommended Posts

lectrotek

Hi all,

 

I'm in a right pickle so any help would be much appreciated.

 

I'm due to hillclimb my G in a couple of weeks but since I got it through MOT it's horrid.

 

Bit of backstory: Bought the car a year ago. Ran rough on idle and had very little power so got the charger re-built at Jabba inc. full service. Performance was like night and day but was still lumpy on idle so unplugged the lambda.

 

Ran better (still not great) until MOT time last month. It failed on a whole load of things, one being emissions which were unsurprisingly through the roof. To get through MOT had to get a new lambda sensor as the old one was fucked apparently when they plugged it in, and fit a new cat as the one on there had been obliterated.

 

So, after much expense (this, welding, steering column, etc.) it got through MOT and felt ok. Drove it 200miles to Devon and back, no probs.

 

After sitting for a week or so last week, went to take it out and all hell broke loose. Wouldn't start (probably battery) so ended up bumping. When it turned over, I couldn't keep it alive. It was idling OK but as soon as I feathered the throttle it'd die. Bumped it again and again with the same result. Managed to limp it back into my driveway with the help of my gf and dad pushing it for a final bump. 

 

Has anyone else experienced this?

 

The only course of action I can think of is unplugging the lambda, and replacing the cat with a straight through pipe.

 

This is driving me nuts! 😬

 

 

Share this post


Link to post
Share on other sites
steveo3002

blue temp sender can cause all sorts of issues ...always use a genuine one

 

these are adjustable via the co pot if i remember right

 

what year is it ...some dont need the cat , but running the o2 sensor should be benefit to how it runs 

Share this post


Link to post
Share on other sites
caretakerplus

Do you know anything about the Lambda sensor that was fitted?

Anything other than a genuine VW or Bosch one could well be suspect - the very cheap ones aren't even worth taking out of their box.

 

As Steveo says, a new (again genuine) blue temperature sensor might be a good investment - if these put out the wrong information, all sorts of problems can result.

 

I can't imagine that leaving it standing for a week would cause any problems, but bump starting certainly can, as with prolonged turning over of the engine without it firing will cause unburned fuel to contaminate the Lambda and also the cat.

 

Regards

 

 

Share this post


Link to post
Share on other sites
steveo3002

as well as the temp sender , you can check the wiring is sound all the way to the ecu with a multimeter , the wiring plug is easy to repair if its weak

 

is the battery /charging system good..i would expect problems with a low charge...again easy to check with a cheap meter

Share this post


Link to post
Share on other sites
lectrotek
2 hours ago, steveo3002 said:

blue temp sender can cause all sorts of issues ...always use a genuine one

 

these are adjustable via the co pot if i remember right

 

what year is it ...some dont need the cat , but running the o2 sensor should be benefit to how it runs 

 

Year is '94. Perhaps the lambda should remain plugged in then if it's beneficial.

 

There is a reciept for the temp sender in all the paperwork so that was changed a year and a half ago 

Share this post


Link to post
Share on other sites
lectrotek
1 hour ago, steveo3002 said:

as well as the temp sender , you can check the wiring is sound all the way to the ecu with a multimeter , the wiring plug is easy to repair if its weak

 

is the battery /charging system good..i would expect problems with a low charge...again easy to check with a cheap meter

Does the battery have an effect on tickover/low revs? if so, that's interesting as I think the battery could do with a change anyway

Share this post


Link to post
Share on other sites
steveo3002

yeah need to check the basics , good charge , good earths

 

the lambda is probably throwing you off ,it should almost the same with or without a working one , the base map should be close enough for it to run very well, the sensor just fine tunes it to make it even closer 

Share this post


Link to post
Share on other sites
lectrotek
30 minutes ago, steveo3002 said:

yeah need to check the basics , good charge , good earths

 

the lambda is probably throwing you off ,it should almost the same with or without a working one , the base map should be close enough for it to run very well, the sensor just fine tunes it to make it even closer 

 

Nice one. That's really interesting.

 

Battery is charging. We'll see what it does tomorrow.

 

Really appreciate the help.

 

Cheers.

 

Tim

Share this post


Link to post
Share on other sites
lectrotek

Right,

Charged the battery overnight and checked the output in the morning. It's solid. No issues there.

Connections at each terminal were a little loose to tightened them up. Car starts, no problem at all.

Issue does not look like it's battery related.

Do you think it could be ecu?  I bloody hope not  :o
 

Share this post


Link to post
Share on other sites
steveo3002

doubt it 

 

have you checked all the other stuff before deciding its the ecu?

Edited by steveo3002

Share this post


Link to post
Share on other sites
MartinB

Hall sender?

Share this post


Link to post
Share on other sites
steveo3002
1 hour ago, MartinB said:

Hall sender?

 

moslty accompanied with the rev counter going berserk

Share this post


Link to post
Share on other sites
G40niko

Have you checked the idle control valve under the inlet manifold could be playing up or sticking.

Share this post


Link to post
Share on other sites
lectrotek

Thanks for these replies guys. On inspection by a man much better qualified than me, the ventilation hose from the cylinder head and the throttle valve is warped, and the aux air valve is buggered. It's been patched up for now but both will need replacing. 

 

The hose looks like it's fairly easy to source but anyone know where i could get an aux air valve? These look like hens' teeth.

 

Cheers,

 

T

Share this post


Link to post
Share on other sites
kiran_182

I got some gt ones

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. Terms of Use Privacy Policy Guidelines