jim21070 2 Posted December 24, 2006 (edited) For a while now I have had the nagging feeling the GTi was not quite "on song". Not as crisp as a 1.6 should be and the idle was not what I would call good, especially with a full electrical load running. The engine had a habit of almost dying when cold or warm and several times it stalled when warm but with the SAD closed. It was notable that when coasting down to a junction from a fair old speed the idle would dip right almost to nothing and then rise. But actually it was all over the place. Not consistent at all. All the symptoms of an air leak really. The other day I cleaned out the inlet tract fully and it seem a little better, not perfect but better. Not right though. It still hunted on idle quite markedly and the difference between lights on and lights off idle was about 300rpm. This afternoon I pulled the inlet tract all apart and in doing so I found a brilliant way of tracing leaks beyond the TB. Simply blow down the SAD hose (it'll be open because everything is cold) and place the palm of your hand across the TB inlet. If you can blpw and create a pressure you know that everything beyond the TB is airtight unless one cylinder is on Overlap when an inlet and exhaust valve is open at the same time. So, I found I could create a pressure by doing this but I should not have been able to as the small vacuum hose from the TB to the oil filler cap was disconnected. I then checked the hole in the TB for this hose and found it well and truely blocked. I reamed it out with a piece of stiff, fine wire and then squirted some carb cleaner down to ensure the hole was really clear. I reassembled and tested. A far better idle, hardly any drop between lights off and on and no idle hunting. A road test made me really smile. All the familiar 1.6 crispness and response was back I came back from a quick test run grinning from ear to ear. So, if all else checks OK and you still have mysterious idle problems, check this little vacuum hole as it is so easily overlooked when doing an inlet overhaul. It sucks quite a lot of dampness,oil mist and mayo so is apt to get blocked. When blocked it'll upset crankcase breathing something rotten and it is easy to see how that then causes running problems. Also you can test your SAD very easily by a) being able to blow down its feed hose cold and when the engine is hot, just after a run, try again and you should be able to create a pressure against the now closed SAD. Edited December 24, 2006 by jim21070 Share this post Link to post Share on other sites
axnutty 10 Posted December 24, 2006 Top top! The old Haynes suggests connecting an airline to the AFM inlet via an adapter (!??!!) and then painting soapy water across all the pipe joints etc. Think I prefer your method somehow! Share this post Link to post Share on other sites
Owain1602 0 Posted December 24, 2006 How about disconnecting igntector plugs and crank the engine with your hand over the throttle body, this is generaly the best method to locate air leaks. But obviously there are variables to the method. Share this post Link to post Share on other sites
boombang 2 Posted December 24, 2006 I've always just put a flat metal plate in front of the AFM. If it doesn't stall there is an airleak. Share this post Link to post Share on other sites
Guest BrainFluid Posted December 24, 2006 Aye, but a good method for finding a blockage were there should not be one tho'. Share this post Link to post Share on other sites
jim21070 2 Posted December 24, 2006 Aye, but a good method for finding a blockage were there should not be one tho'. Yep, more by luck than judgement though It has made a heck of a difference, unblocking that tiny little hole. Fair made my Christmas it has... Share this post Link to post Share on other sites
Guest BrainFluid Posted December 25, 2006 Merry christmas Jim Share this post Link to post Share on other sites
