Guest sophieisking Posted May 29, 2009 Share Posted May 29, 2009 (edited) Help! I have a beautiful Mk5 Cabby, 91 reg 1.6. The car starts perfectly but revs really high at the start, 5000 rpm! Then it gradually settles down at 3000 rpm. After a couple of minutes of driving, when I get to a junction and it's sitting in neutral, the engine revs itself, from 2500 rpm up to 5000 rpm and back down again, it has a life of it's own! Then when this has happened for a while, she will sometimes stall when pulling away from a junction, or when going from reverse to first when parking. Very strange. I'm a girl so not excellent with cars but I have cleaned the fuel injectors and the Idle air control filter seems fine. Also I cleaned out the throttle body with Carb cleaner and it's still running the same! Please help with the diagnosis! I'm gonna try and do the work myself. P.s. I'm looking for full leather interior and a Mohair roof for my Mk5 cabby if anyone knows where I can grab a bargain? Thank you, XXX Edited May 29, 2009 by sophieisking Quote Link to comment Share on other sites More sharing options...
Admin Paul Posted May 29, 2009 Admin Share Posted May 29, 2009 Idle control valve is the common fault, else you have a air leak on the system. Paul Quote Link to comment Share on other sites More sharing options...
Guest Sharkey Posted May 29, 2009 Share Posted May 29, 2009 Also Lambda sensors are another possible cause. air filter may need changing. Could be mass air flow sensor. It needs plugging in to a machine!!! Quote Link to comment Share on other sites More sharing options...
Guest sophieisking Posted May 31, 2009 Share Posted May 31, 2009 Cool, I think it might be the lambda sensor because I read up on it and the symptoms are everything that i've got, surging, stalling, high emissions, high fuel usage. Is this easy to replace...or even clean! And, stupid question, where can i find it on my Mk5?? Thanks guys. xxx Quote Link to comment Share on other sites More sharing options...
Guest magic rat Posted May 31, 2009 Share Posted May 31, 2009 The sensor is in the front downpipe, if you look under the front of the car its fairly obvious (looks a bit like a small spark plug). I got a replacement from cats2go for I think about 25 quid and fitting took about 10 minutes. (The hardest part was getting the old one out) I didn't have any of the symptoms you've described but it failed the MOT emissions test on the old sensor. Quote Link to comment Share on other sites More sharing options...
Guest Eggsy Posted June 2, 2009 Share Posted June 2, 2009 check all pipes around manifold - some of mine blew of today - had me baffled for 1/2hr!!! lol Quote Link to comment Share on other sites More sharing options...
Guest sophieisking Posted June 2, 2009 Share Posted June 2, 2009 Thanks Eggsy, So turns out that the Lambda sensor has made a difference, but the big problem was my thermostat, it was leaking air into the cooling system and so pressure was building up in and around the throttle body too, causing it to rev and lose throttle power. It finally over heated yesterday due to the hot hot weather and that's how we found the problem. Going to remove the thermostat and radiator flush it, see if it runs ok like that, then if not..............heaven forbid.........it's the head gasket!!!!!!!!!!!!! I'll keep you posted. Quote Link to comment Share on other sites More sharing options...
Guest Eggsy Posted June 2, 2009 Share Posted June 2, 2009 check your thermostat (remove & put into a bowl of boiling water see if it opens) also check your water pump is working properly & last but not least do a pressure test on your cyclinder & check oil for a creamy coloured sludge (headgasket) Quote Link to comment Share on other sites More sharing options...
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