light misfire

[flatcap1]

i have a 2000 plate 1,8 20v passat, atp engine, and my car is fine on driving but when just breezing lightly on throttle say at 60 mph and trying to hold that speed by lightly touching throttle car feels like its misfiring,i have changed oil and filter,fuel filter, plugs,air filter,pollen filter,had all belts changed, has anyone any ideas, would changing ht leads and clean throttle body solve my problem?

[bristlenose]

you've not mentioned millage but i've had this problem for years now,started at 80k now upto 175k.
If when car is up to temp,try bringing the revs up very slowly until you reach 1200 rpm.does the car seem to try and stall recorrect and so on.this throttle position would almost be the same as driving at 60 mph.
regards andy

[flatcap1]

thanks andy, my passat has done 102000 miles, no car doesn't try and stall. revs normally,but at traffic lights it feels like a missfire like a pop inside the exhaust and it feels like someone has nudged the car, then ticks over happily for a bit then the same again. any thoughts. have you never solved your issue, i still think clean my amf, then throttle body should solve it, me hopes.

[bristlenose]

no,i've not solved it as yet. Spoke to my local vw tech man and got a "well what do you exspect with that millage response".He did reset the basic setting on the throttle body but no improvement there.when i sugested a throttle body clean he advised me to not try and do it connected so as to retain the basic setting as this my blow the ecu.
I still feel it is down to an air leak or fuelling prob.I don't know but with my millage now i wont be spending too many beer tokens on this one.

[andy e]

look at the vacuum pipes i had this problem, light misfire on tickove,r found a split in a pipe replaced it no problems so far, 1.8 apt engine 105000 miles

[bristlenose]

had a good look at vac pipes now we have good weather.
you were spot on andy e. it was not looking good around the throttle body.found three hoses with terminal eczema.
the photo shows why idle and general running can be badly affected by abnormal air intake.
have done a temp cut back till i can order parts monday.
regards,
andy

[flatcap1]

thanks for your help chaps, i have changed my vac pipes, changed one of the pipes from the tube going onto the tb, and a plastic breather tube from side of engine going into a condenser box, on a diagnostic machine it is telling me, i have a week left bank injector and a faulty 02 censor, but now pipes cleaned and changed may go away, hasn't been back on since to know if it has, now i'm trying some forte fuel system cleaner n hoping it will clear my injectors and help with my emmisions, as it only just passed with 0.299, only allowed 0.3 before a fail.

[scotty33]

If the o2 sensor IS faulty, this could cause the emissions to be high, (along with fuel consumption)

[flatcap1]

i'm not too sure how many 02 sensors are on the atp 1.8 20v engine i think 2, have you any idea which one its likely to be and where is it, thanks again scotty.

[scotty33]

If there are 2, the first one will be before the cat, i.e it could be on rhe cat itself but at the front, sometimes they are fitted to the exhaust manifold. The second probe I think is after the cat, but could be at the back of the cat.
http://www.lambdasensor.com/main/mpos.htm

http://www.lambdasensor.com/main/mtesting.htm

a fault code read will only pick up a lambda sensor fault if it has gone open circuit or shorted, at some point.

[flatcap1]

i have now run the forte injection cleaner through, no difference, around 2800 revs in third gear hold it there n its like havin a case of the dt's, legs feel like they are bouncing ,like ditherring, same in 5th gear but not as bad, i'm a bit stuffed now whats the root cause, do you reckon it could be the o2 sensor/sensors, still not sure if it has 1 or 2. after 3000 revs car fine, a little flat spot tho when putting boot down,