It may be something to do with the buildup of crud in the throttle bodies I've heard this before.
Have you been using cheap supermarket petrol?
I used to, but got a slightly erratic idle, switched to optimax this made things better straight away although this was a short rough spot after a few weeks I put this down to the gunk gettting cleared out.
I always use optimax in mine now havent had anything like that in 6 months and the performance/economy is better as well..
<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:<hr /><font size="1" face="Verdana, Helvetica, sans-serif">Originally posted by lee2003:
<strong>anybody have any ideas why the tickover on my 156 is erratic?</strong><hr /></blockquote><font size="1" face="Verdana, Helvetica, sans-serif">ive been using texaco petrol but ill give optimax a go thanx
You need to clean the throttle bodies and unplug and replug ECU and various other plugs, temp sensor etc. However be very careful as the pins are easily bent and then you'll have all sorts of problems, take it to a specialist if you aren't sure.
Other causes are a knackered stepper motor or lambda sensor. Problem is when one fails the others compensate so narrowing it down to one thing is a nightmare so start by cleaning everything.
cleaning the throttle body should help, and using branded petrol, too. I had a similar problem with higher-than-normal idle speed. I'd cleaned the throttle body a month back, and it's now back to normal.
Here's how you can access it, remove the main air hose first: