running on 3 cylinders/ misfire. help needed :(

xCoupexAshx

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hey guys, need your greatest of help please. ill start at the beginning..

driving the other night and coming down the road, after a bit of a run. and suddenly car dropped down to 3 cylinders. so pulled into the garage n after a bit sorted it self out. so carried on and it happened again. so turned it off n left it. mate told me to reset the ecu (disconnect the battery, brake down 10 secs) and it worked fine n managed to get it home. then tested next day n it drove fine till afternoon, n happened again, so i reset it n got it home once more.

next day took it to my mates garage so we could have a look, got a new coil pack as i suspected it might be the dreaded 3rd cylinder ive read so much about on here, swapped that over. seemed to do the trick, started driving home. but after a mile, happened again, so drove back. the problem found is its not sparking in the 3rd cylinder (third one from the right) the other 3 are working fine as far as i know, as in when the lead from the back of the 3rd cylinder is pulled out theres no difference in the running of the car, yet when you pull any of the other 3 leads that go into the coil packs out, you feel the car drop down. so after 3 hours playing under the bonnet im still stuck. we tried swapping the coil packs round + trying a new coil pack. also tried new spark plugs and swapping them round and still no difference. =[

today ive tried a new ignition amplifier as i been told it could be this and still no luck. still same problem. tested all other sensors too such as MAS (new one put in only a year ago) and few others.

so i been told could be one of few things left. 1) problem with the ECU. 2) problem with wiring or 3) timing belt skipped a tooth

any insight on this or anyone that had the same problem would be much appreciated.

car = 98 a3 1.8t 8l agu code

(btw sorry long winded, just trying to give all the infomation i can :])

thanks in advance, Ash