T4 petrol 2.5 litre Petrol Can Hear You Knocking

[GregC]

Had a VW guy hook up the computer the other day and the engine is struggling to find TDC (his words not mine) He suggested that when the car was last serviced (by a reputable mechanic) he didn't do a full job and as such the distributor had been advanced but the computer was trying to retard the distributor and that was causing the knocking. Anyway, the question remains, I have a knocking in 5th especially when under load the engine is running rough as. The other side of the coin is that it isn't running like engine is too far advanced or the timing is out, its not getting too hot and it certainly isn't losing power (although it must be said that the old girl is certainly not exactly a drag car at all).

Talked to another mechanic today and he suggested it sounded like the distributor itself needed replacing. I am open to suggestions and any sage like advice would be appreciated.

[Sunny43.5]

I know its an obvoius question but what fuel are you using 91 -95 -98 RON don,t whatever you do use these blended E10 fuels nothing but a disaster waiting to kill an engine , I have found big differences in the supposed RON content of the fuels at servos these days . If I fill my van up with 91 RON rated fuel at a service station it will trigger the engine fault light if I then fill from a different servo with the same RON fuel it will be fine and the light goes out . I believe that the fuel companies are not exactly truthful or honest when it comes to the RON content in their fuel My son has T4 2.5 and I tell him to run the 95 Ron as his will knock if on the lower 91 RON .

[GregC]

I only ever use 98 for petrol and in the event of using a 95 it gets an octane booster put in at the same time.

[Silver Caravelle]

Had a VW guy hook up the computer the other day and the engine is struggling to find TDC (his words not mine) He suggested that when the car was last serviced (by a reputable mechanic) he didn't do a full job and as such the distributor had been advanced but the computer was trying to retard the distributor and that was causing the knocking. Anyway, the question remains, I have a knocking in 5th especially when under load the engine is running rough as. The other side of the coin is that it isn't running like engine is too far advanced or the timing is out, its not getting too hot and it certainly isn't losing power (although it must be said that the old girl is certainly not exactly a drag car at all).

Talked to another mechanic today and he suggested it sounded like the distributor itself needed replacing. I am open to suggestions and any sage like advice would be appreciated.

Sounds a bit drastic to replace the distributor without some basic mechanical checks and adjustment first.

Knock sensors on Engine Block at front Ok?

Could be the distributor needs loosening a turning slightly. The bush mechanics way is to run the engine to full operating temperature and idle and turn it so it is neither sounding advanced or retarded. This should put it 'mid way' in terms of timing so the computer can then correctly and automatically adjust the timing and the knock sensors retard timing as it advances to the knock limit under acceleration/load.

Could be dodgy fuel and perhaps try a change of spark plugs and leads.

Might be worth hooking it up to a computer to see if a fault is logged.

Cheers, Scott

[GregC]

Looks like the distributor needs to be replaced. Im a touch confused as I have been told that a distributor will take approximately 6 hours to change out. Looking under the bonnet that sort of time seems a bit rich, any thoughts??

[Silver Caravelle]

Hi Greg,

I wondered how you got on with this. Did you get a chance rule out the other stuff I mentioned first?

Assuming it is something to do with the distributor, I reckon it needs to be loosened and retarded slightly to put it back within the range that the ECU can cope with automatically adjusting the timing.

In relation to removing and replacing the distributor on a T4 it is pretty conventional and I recall it is held in place by one two clamp bolts and pulled straight out of the side of the engine. I can't see that taking 6 hours!! Maybe a second opinion is warranted from another mob in ACT.

Regards,

Scott

[Sunny43.5]

Isn,t it nice to see the old fashioned methods that can be done on the older series I remember the days when you used a timing light and adjusted the dizzie by hand to get the performance . These days not so easy hmmmmm I must be old .

[GregC]

Yea Scott my normal mechanic sent me off to the dealer cause he thought it may have been the actual engine sensor, however, the dealer is telling me its the distributor itself. They quoted me $1100 to do the job and Im thinking that seems quite expensive. My mechanic is now sourcing me a distributor and I would be surprised if the whole job took more than an hour to complete. I would also think that a second hand distributor would do the job as this is quite a rare thing to happen apparently.

[Silver Caravelle]

HI Greg,

Your mechanic is on the right path and it should take no more than a hour as you indicate. Even new distributors for this vintage aren't super expensive. Apart from, say a wiring issue, they are pretty straight forward unless it gets a little worn and therefore a little extra play in it. This might mean a little pinging under load. I can't but think though the existing one needs to be turned very slightly to put back into the baseline range for the ECU to automatically adjust the ignition timing within the baseline range (if that makes sense). Some times these can be very slighty out of wack after a cambelt change.

On my old T4 Caravelle (2000) model pinged a bit even with newish spark plugs. I was suspicious of these and actually swaped out the plugs and the pinging went away.

Also a good 'italian tune up' always helps to clear a bit of carbon out from around the inlet/exhaust valves - which can be a source of pinging.

All the best. Scott

Regards,

Scott

[GregC2]

hey guys, I had to sign up again and Im now GregC2. Latest happenings with the Distributor is that I am getting a replacement from VW, total cost.............$830. Yep that is right although they do give me $300 back when I return my old one. Seems a tad expensive to me, anyway, as I cant find a second hand one anywhere I am stuck with a price that is larger than your average 3rd world countries foriegn debt.