Misfiring Vw Golf Mk4 Help!

Hi I was wondering if anyone could help I have had my mk golf 1999 auto AEH for about 4 months now and have been have a misfiring problem with it. I have had a mechanis look at it he advisded me to change plugs lead and coil I did this and the car was running fine for a about a day then started to misfire again, I then had a diognostic done and it came up with hall senor no signal please could anyone advise me on what the hall sensor does and wheather it will sort my misfire problem out, it just seems to be one thing after the other if anyone can help I would really be grateful.


Thanks

Im having difficulties with my car too..it seems to misfire, the revs move up and down, however they do become stable sometimes, it is so annoying though..what could the probem be???

i've been reading up on various articles, theres so many suggestions, the most popular one(s) being:
~ coil pack
~ spark plugs
~ egr valve
~....etc

How would you know which one is to be replaced??
It costs an arm and a leg to get all of them changed, especially when labour cost more than the parts sometimes, theres no point tryin trial and error unless uv got money pourin outta yo backside..

I hope someone can help..would really appreciate it.

Cheerz (",)

And the car is a Golf 4 what?

its a golf mk4 1.8 gti turbo (registered 2000-X plate)

It would be, right on the change point of engines. What is your engine code AGU, ARZ or AUM?

Hiya Crasher dude, the engine code is AUM.
Cheerz

Well the first thing I am going to suggest is the usual fault code read, print and clear and then re-read to see if any codes re-appear immediately and if some do, they can be dealt with. If a faulty coolant temperature sender comes up, I suggest you have it replaced. Whilst the car is at the garage having the fault codes read, I suggest you ask for the throttle body to be removed and cleaned, then the ECU adaptations cleared and finally the ECU re-adapted to the throttle body and if the garage knows how to do it, the emissions system checked by manually generating what is known as the “readiness code”. Take the car away and see how it drives for a week or so and then go back for a re-read of the codes at which point any further problems you have been having should have generated a fault code which can be compared against the original read to see if it is a reoccurring code. During this period between reads it is vitally important that the engine is not played about with and that nothing in the engine bay is disconnected with the ignition on or the engine running. The AUM engine management system can accurately pin point a misfiring cylinder and therefore a faulty coil pack but from what you are describing I doubt if you have a failed coil pack as these just fail and that is it, they never work again.

hi, i also have a Mk4 with an AUM engine experiencing the same faults!!! sometimes the car works without showing any symptoms but other times it suffers from erratic idling etc... took it to a mate at VW and got it diagnosed. it was recording misfires on all 4 cylinders. after looking about the engine, he found 2 breather pipes were leaking so i had them replaced at 30 quid a pop. this seemed to do the trick for about a week, now were bak 2 square 1. like you say trial and error aint cheap! when i was connected to the diagnostics at VW, an error came up stating that the DumpValve had mechanically malfunctioned. I am now thinking of replacing this part. i have found a standard replacement for 22 quid. this may or may not be the problem that you are also experiencing. apparantly faulty or blocked breathers can cause the symptoms that you are stating so idd check all the pipes n tubes are in good nick.
if you solve ur mystery it would be nice to know how!

If the code you got was 00575 and was interpreted by VAG-COM as DV failure (Diverter Valve, not Dump Valve, this is not a Chav car), this is usually wrong and more often than not is just a dirty throttle body. The DV is easy to check, take off the vacuum pipe on top and attach another piece of 3-mm vacuum pipe, suck on the pipe and if you can suck air through it, it is faulty.

yeah i got the throttle body cleaned when i changed the breathers. just kept foot down on the accelerator n my mate cleaned it with a rag. This sufficient? havnt had chance to check the diverter valve as i aint got a jubilee clip to replace the crimp currently in place. hope to do that soon. whats boggling me is that the car only seems to misfire when the engines cold at startup. this is not the case all of the time tho, like this morning, my car was frozen cos it was soo cold but it started fine streight away! i took it for a long 2 hour drive to manchester on weekend and it was fine all of the way there and back. it had a lil niggle when i started it up to come back but on the motorways it was fine! getting average mpg too, 31 mpg on the motorway, so i dont think its misfiring when im driving and not noticing.
oh since my last post, ive changed my plugs. Stil not improved things, althogh i didnt believe this would anyways, i just didnt know when they were last changed so...