2.8 Cough / Jerk

[slabber]

Hi Folks

I’d be grateful if anyone has any ideas about the following problem with my 1998 A6 2.8 Q tip saloon: When I’m driving along at a lowish speed (below about 60 mph) and a high gear and press the accelerator to increase the engine revs (for example to keep at the same speed when meeting an incline), the car will frequently cough / jerk (once or twice, very quickly) before the engine picks up speed. It’s been doing this for some time, and I’ve always assumed it is the engine doing the cough / jerk thing, although I can’t be absolutely certain that it’s not the transmission. The problem doesn’t happen when the engine isn’t under load – accelerating down a hill for example is fine.

I frequently monitor for fault codes using VCDS but nothing has ever cropped up, and the car is regularly serviced at an independent Audi specialist. Apart from the cough / jerk problem the engine runs very smoothly, and the automatic transmission seems fine as well – no jerks or anything similar when changing gear. In recent months I’ve had the throttle body cleaned and the MAF replaced but this has had no effect.

I’ve spent ages trawling through forums but have found nothing. This is starting to drive me mad so any suggestions gratefully received!

Cheers - Graham

 

[andyquattro]

Found this thread HERE from another forum. Hope it's useful!

I'm not too familiar with the 30v only the 12v which I had in my last coupe. Sounds like a misfire/weak spark which will be more apparent in high gear low revs and accelerating, could be plugs lead or maybe the coil pack!

I know with vagcom you can log misfire's from each cylinder with the 1.8t but not sure if you can with the 30v, worth looking into. Dont think it shows as a fault code until you get multiple misfire's over a short time.

 

[slabber]

Thanks for taking the trouble to find that link Andy - really appreciate it. Bit of a long shot but I'll try to get in touch with the OP and see if he fixed the problem. If this doesn't work, following your comments I think I'll change plugs/leads and coil for starters - hopefully not too much money wasted if they are not the problem. Do you know how this kit is configured in the 30V? I have an A3 with the 1.8T and changed the plugs and 4 coil packs myself with little difficulty. Just wondering if the 30V is separate coil packs or more likely from your description one coil with 6 leads? (Apologies if that's rubbish - I really have no idea.) Anyone got any recommendations for the best place to get this kind of kit - possibly online?

Cheers - Graham

 

[andyquattro]

Here's a pic of the 30v with the cover removed, very similar to the 12v. Coil pack at the front of the engine!

eurocarparts sell's plugs and two makes of coil one £75 and the other £160 there is plugs, leads and the coil's on fleabay! Maybe a spark tester would be a good investment before buying the whole lot.

 

[s3tle]

If you can find someone near you with vagcom, you can log channels 14,15,16 to see which cylinders are misfiring and how often. Unless the misfire is very bad it won't flag up a fault code and if it did that the engine management light would flash on as it is misfiring.

i just did this on my 1.8t to see which ignition coil had failed, 20mph + 4th gear + foot down, tiggered a misfire at 2k rpm on my 1.8t which i could then log in vagcom, not so helpful as you've only got one coilpack but at least you could check it is a misfire problem and check the plug first?

 

[slabber]

Thanks for the replies! Apologies for not replying sooner - been away for a family birthday up north. Lots to work on this coming weekend - I do have VAG-COM (or VCDS as they call it now) so I'll RTFM and work out how to log misfires. If I can confirm that then hopefully just a matter of replacing part$ until problem solved. I've just found a site where there is a dedicated forum for the 2.8 30V (http://forums.vwvortex.com/zeroforum?id=34) so I'll have a nose round there and maybe repeat my question in case there are any more suggestions for parts to replace.

I'll update this thread with developments.

Thanks again - Graham

 

[a6andy]

I had a simular problem on my 2.7 bi turbo turned out to be the air flow meter maybe worth a try for about £100

 

[slabber]

Thanks for the MAF thought Andy. I had that replaced a while back but wasn’t the problem. I feel I’m getting warmer though...

Latest is that I tried to use VCDS (latest version) to log misfires, but channels 14, 15 and 16 didn’t have anything to do with misfires as per the manual. I managed to buy a second hand coil pack off Ebay for £18 including postage. I fitted that but that didn’t fix it however at least I’ve eliminated an expensive part as the culprit. Next task is to buy plugs and leads and hopefully get them fitted at the weekend.

 

[slabber]

Quick update: A very helpful chap at GSF advised only replacing the plugs in the first instance. Did that - problem all sorted! What was disconcerting though was that all the spark plug 'tubes' (ie where the leads fit) were full of oil. No idea when the plugs were last changed so not sure how long they have been getting this extra lubrication. I'll check in the next couple of weeks to see if the oil has returned, but meantime should I be too worried about this? Engine has done 143k and (now) runs very nicely.

 

[The Slug]

have you checked your oil level?

 

[slabber]

have you checked your oil level?

My wife's away at her sister's at the moment with the A6 so I haven't had chance to check. Could you say more about the oil level thing? The car was only serviced a couple of months ago and I haven't topped up since. Can oiled plugs result from overfilling with oil? The plugs didn't look as if they had been changed for ages so they might have had oil on them for a long time.

 

[The Slug]

im no mechanic, but possibly yes.....