My engine earth strap corroded and broke causing a few hot start issues as expected with restricted earth.

Fitted a new earth strap, engine runs smoother, no hot start issues (ie not hammering battery anymore).

Except now it doesnt idle properly all the time and about 50% of the time on dropping the clutch it stalls or almost stalls.

Reset the ECU (p8) and its a bit better but still drops off and stalls a bit.

Any idea why correcting the earth would screw up the idle? Id of thought it would idle higher if anything not lower.

any ideas??

 

anyone any idea?

 

Sounds like you probably have more than one issue, depending on how electrically minded you are if your car has a rotted out earth strap between the chassis and engine there is a strong chance corrosion is not just isolated to that, easy thing to start can of wd40 unplug everything clean, spray and refit, not trying to sound condressending but if you give a little indication of what you can do it would be easier to give you things to check and try that you understand as with everthing never overlook the simple things first.

 

Usual problem is someone at some time in the cars life mapped it with a bad earth and when you fix it your fuel table is well over populated.

 

As per Stu, the cable was obviously on the way out when mapped

 

wouldnt surprise me stu. i replaced all the battery wiring last year as being in the boot pumabodge used quite small battery cable and more worryingly speaker cable for the battery earth no wonder it was slow to crank all that was sorted last year so only earth strap left to change is starter motor to chassis.

Wonder how many hours on the rollers it will take to sort out that then! might as well get the cruise map sorted too to get decent off boost economy.

 

Cant have been, it would have melted surely.

 

also must have been oxygen free speaker cable, or else it would have caught fire

 

It wasnt small 5amp speaker cable but that thicker stuff as a twin core. Something like this:

 

Surely whoever mapped the car in the first place would of checked for things like this ?

 

i have a similiar issue when i push the clucth down on my cossie, idle drops low and then the iscv catches it. I'm not sure why but my car was mapped at EP, the same as your i believe.

 

In my experience most so called mappers dont even check teh sensors all work before diving in and slagging off your map and saying how they can make it better and mapping round simple faults for you. Woe betide anyone who then goes and fixes something. LOL


It wont have been like that right after mapping though I assume otherwise the idle sites couldnt have been mapped properly and nor could the idle drive targets, so something must have changed since your mapping session?

 

Get it down to turbosystems Warren, only just round the corner for you.
After reading this, and me nearly setting fire to my car a while ago after forgetting to refit my main earth cable and trying to start it i will be making up a few new /extra earth cables for mine tomorrow before its mapped.

 

Im replacing the starter earth over the weekend to be sure anyway.

Everyone keeps trying to say i need a direct starter to battery earth lead. Surely that is bollocks when both the battery and starter are earthed to the massive metal chassis Even a beefy thick copper cable surely isnt going to be better than the chassis as a whole for earthing.

 

Wheoever "Everyone" is, he's wrong.