1.8T Battery Died. Now rough Idle, Help Please.

[portsA318T]

Hi Guys. Last weekend my battery went *** up over a couple of days. Before this the car was idling fine. Now with a new battery in place the idle is really poor between 750/850rpm and it fluctuates almost to a stall when slowing down. When stationary its fine. Any use of the go pedal will make it rough when the rpm comes down. Driving isn't a problem.

How do i go about adjusting the idle back or at least to sort it out? Thanks in advance.

 

[Clach]

Have you checked around the MAF. My car was the same as the garage forgot to tighten the jubillee clip on the air intake. Could be a dodgy MAF sensor also?

 

[AndyMac]

After a battery disconenct it takes a while for the ECU to relearn everything and adjust accordingly. 8 hours driving should give it enough time.
Having said that it could be something more involved, either temp sender (easy) or water pump seizing up (which is what happened to my A4) luckily it was also leaking slightly so was easily spotted. When they changed it along with the cambelt/idler etc the water pump was so corroded you couldn't even turn it by hand.
The temp sender is a common fault and provides the ECU with temp data, so if it's giving duff info then it can effect idle by overfuelling or under fuelling as well as poor performance and heavy fuel consumption. For £20 and a DIY fitment it's worth changing (if it hasn't already been changed) before doing anything else.
Of course it could be a host of other things, but you shouldn't need to adjust the idle as this will be just masking the actual problem.

 

[h100vw]

You can 't adjust the tickover speed like in the olden days.

If it was OK before the battery died, then I would assume the engine to be basically sound.

Have you got access to VAG-COM? If you do then scan it. A throttle body alignment may fix it.

If not then I would disconnect the battery for 10 minutes and then see how it goes.

If you have an early car with AGU motor, when you first turn it back on, just sit there for a couple of minutes with the ignition lights on. It should do an alignment if it thinks it needs too.

HTH

Gavin

 

[portsA318T]

After a battery disconenct it takes a while for the ECU to relearn everything and adjust accordingly. 8 hours driving should give it enough time.

I'm hoping its just that. The car was fine before and even now, other than the poor idle, it runs perfect with no peformance issues.

 

[james0808]

I had this on my golf years ago,i reset the throttle thingy and all was fine again.

 

[portsA318T]

Have you got access to VAG-COM? If you do then scan it. A throttle body alignment may fix it.

If not then I would disconnect the battery for 10 minutes and then see how it goes.

If you have an early car with AGU motor, when you first turn it back on, just sit there for a couple of minutes with the ignition lights on. It should do an alignment if it thinks it needs too.

HTH

Gavin

No VAG COM unfortunatly.

Is that a proven adjustment with the ignition lights left on?

 

[james0808]

If you have an early car with AGU motor, when you first turn it back on, just sit there for a couple of minutes with the ignition lights on. It should do an alignment if it thinks it needs too.

Thats all i did.IGN on,leave for 2 mins then start engine.

 

[james0808]

Forgot to add i did give the throttle body a good clean too.

 

[portsA318T]

Well the disconnect reconnect worked....to a degree. Reset it and started again and great.... went back to how it was. Even blipped the throttle and again no fluctuations. Turned it off, closed the hood etc went to start it again and...yep...back to how it was.

Should i have taken the car for a run after the first start to train the ECU back to how it was before the battery went......???

 

[james0808]

Have you cleaned the throttle body?

 

[andyccr]

Octavias do this as well. The solution was to reconnect the battery, turn ignition on for about 30 seconds and if you have the 'fly by wire' throttle body you can actually hear the throttle body resetting itself. Wait until you can't hear the noise from the throttle housing anymore

Regards,

Andy

 

[portsA318T]

Have you cleaned the throttle body?

Nope, at work you see. Plus apart from a fuse, battery, DV and some other bits i'm an engine noob. Where is it located?


Why can things be easier. Change, turn on, and go. Thats how it should be.......

 

[james0808]

Nope, at work you see. Plus apart from a fuse, battery, DV and some other bits i'm an engine noob. Where is it located?


Why can things be easier. Change, turn on, and go. Thats how it should be.......

Follow the rubber boost hose from the intercooler up to the inlet manifold,undo it and clean all the crap out and reset the throttle.

 

[danneth]

i had the extact same problem this weekend, so i read this thread and tried what someone said with leaving the ignition for 30 seconds then starting the car worked a treat for me