Hi, i've got a mk2 8v, completely standard from when it left the factory. When i got the car in the 'height' of summer, the idle was superb... low, deep with a really even beat and comfortable to sit in the car. I remember thinking how impressed i was. Ever since it had it's timing belt changed in September, the idle just hasn't felt the same. I wanted to have the belt changed as it was due and thought that my timing was out due to a persistent shunt on initial throttle application & violent bucking at cruising speed problem when coming on and off the accelerator - which i now think is engine mount related. The mechanic who changed belt, who is a sort of mate of my dad's, used to work at a Merc dealer and does appear to know his stuff. He told me the timing was spot on before and that this wasn't the problem. However, as soon as picked the car up, it didn't feel quite as rock steady at idle - even though the needle doesn't budge from 900rpm - it just feels lumpier, sounds funny & sounds like it's missing. Could this just be a coincidence that this started happening at a time when the weather started to get colder. I have no loping idle symtpoms but occasionally recently, the car seems like it's gonna stall when started from cold and sometimes cuts out soon after starting when braking and coming to a stop. Have taken out idle screw, cleaned it but havcen't touched ISV. The blue coolant temp sensor was replaced by VW dealer about 3 years ago as it was faulty. AFAIK, i have no leaks in the intake system etc. Is it possible my mechanic ballsed up the timing thing by not "2250rpm'ing" it? Is this sort of behaviour typical digifant cold start/general idle behaviour? thanks very much in advance as i don't wanna blame my mechanic if this has nothing to do with him, Luke
Unlikely to be cam timing IMO. Sounds like ISV clogging and its possibly worth checking your throttle switches too.
Before you get too involved, make sure the igition timing is spot on. It does need to be done at around 2250 RPM with the blue temp sender disconnected (blip the throttle three times over 3 000 RPM) or you might as well not bother. Then clean the ISV and reset the base idle as per FAQs. You might also want to take the timing belt covers off and make sure that the cam is timed up correctly but the the loss of power if it was a tooth out is normally very noticable.
Get him to recheck the timing. did he readjust it after changing the belt. if the car has been timed with an old belt it will need redoing when you change the belt. this is because your old belt would have streched a bit over time. and make sure he follows the correct procedure (setting idel and disconecting temp plug etc) if that was the only thing he done on the car i definatly say it was the timing.
thanks guys, Could be wrong but it doesn't feel like i'm losing any power. the things revs beautifully. It's not as quick as my BBR MX5 but it's very torquey low-down and pulls pretty hard at 4-6k rpm. the car was owned by the same 'disctrict-nurse' lady from new so i know it's not been hammered at all. has done 130k miles though. problem with your advice is a) i don't have a strobe light gun and b) i truly wouldn't know what to do with it if i did. i am a numpty in that respect. so, how about i take the isv off and clean that to see if it makes a difference? it just seems odd to me that before cam-belt change, i couldn't fault it and after, i could. once again, thanks in advance. Luke
Check the bung in the rocker cover for splits too... If the idle is slightly lumpy id hazard a guess at an air leak... The throttle body rubber blanks can also perish & introduce air leaks too..
