1998 A6 mis-firing.

[teersy]

Hi all,
Just recently joined this forum in search of help/advice if posssible.
My old boy A6 has developed a 'missing' mainly when the engine is under demand i.e. when accelerating, going up hills etc.
No relevent fault codes are produced - although an engine coolant sensor fault reared its head.
The plugs have been changed: fault still apparent.
The car is at our local garage, he thinks its the coil pack(?). Are his thoughts on track?
The car idles fine, no missing. So testing leads etc is not possible (he says).
My experience is very limited in this area so please any advice would be much appreciated.
Jase.

[Niall76]

I had this problem a while ago - it was the HT leads. Slapped in a new set and all was good.

Eurocarparts - about 60 for a V6 set as oppsed to 250 from the *******.....

[audipersempre]

Coil packs are a possibility, I had the same symptoms on a BMW 325i and this cured it but it is an expensive guess particulrly if it doesn't solve the problem!

Maybe try to HT leads first?

[teersy]

Thanks for your help fella's,
I'll do just that and go for the leads first.
If it cures the problem I'll post back here for future reference to others.
All the best,
Jase :o

[lonky]

As you have got ride of the spark plug issue, then the coil pack is the next logical place.

[martin4play]

Also check the "pulse" on the injectors

[teersy]

Hi all,
No good news here, unfortunately. Plugs, leads and coil pack changed - fault still apparent. Perhaps I've described the fault incorrectly.
The car accelerates with a defined juddering up until you enter a high rev value, say, 3000+. The juddering is not uniform. It's like it's missing but also like the timing's out. I haven't had any belts repalced.
The garage I had the car at said there were no faults brought up on the diagnostics.
Fuel management? ECU management?
These engines are complex with many sensors. If the sensors are working but the item which feeds the sensor is at fault i.e. pipe etc could this be a problem. I'm not experienced in this matter just airing some thoughts.
Any help appreciated.
Jase.

P.S. Although they are very expensive I may drop it into an audi garage for fault finding.

[audipersempre]

Sorry to hear you still have the problems. Could it be fuel rather than spark? Injectors, fuel pump etc?

I wouldn't hold out too much hope of Audi finding the problem. If the onboard diagnostics don't find it the Audi guys in my experience are no better clued up than a non franchised garage sadly.

Could not find what was causing the battery to go flat on the TT we used to have. Went in to Audi three times and they could find nothing, neither could the AA man. Gave the car to a local guy who fits car stereos, sat nav's etc. In 30 minutes he diagnosed a faulty tracker unit draining the battery. I didn't even know it had a tracker unit fitted!

[buster]

Hi all,
No good news here, unfortunately. Plugs, leads and coil pack changed - fault still apparent. Perhaps I've described the fault incorrectly.
The car accelerates with a defined juddering up until you enter a high rev value, say, 3000+. The juddering is not uniform. It's like it's missing but also like the timing's out. I haven't had any belts repalced.
The garage I had the car at said there were no faults brought up on the diagnostics.
Fuel management? ECU management?
These engines are complex with many sensors. If the sensors are working but the item which feeds the sensor is at fault i.e. pipe etc could this be a problem. I'm not experienced in this matter just airing some thoughts.
Any help appreciated.
Jase.

P.S. Although they are very expensive I may drop it into an audi garage for fault finding.

In my experience there is only one way to sort this properly and that is to find a diagnostic unit with a rolling road.

Just an idea :cool:

[martin4play]

In the old days ----- showing my age here !! What you describe is like "pinking" thats mixture of fuel/air [ remember the dreaded Zenith Carb :aargh4: ! ] Ok cars these days ---- ecu,map, and loads of sensiors ! but the problem does sound like its a fuel problem --- change fuel filter ? Could be water in fuel tank ----- just a wild guess !
As said in the above thread "rolling road " ------ yes good idea :biglaugh: but were getting to more expensive fault finding
Just a thought when it is juddering if you put your foot on clutch [ oh u mite have auto ! ] and you increase rev s ,is it still there ?

Just a few thoughts i was thinking !

[Niall76]

This sounds like a bit of a pian. I read over your first post again and it is exactly the same symptoms I had. When was the car last serviced? And do you know if the fuel filter was changed?

[teersy]

Hi,
The car has just had an annual inspection. I was told all the filters including the fuel filter was changed.
Jase

[teersy]

Thanks for all your thoughts,
I'll keep this forum posted with further progress for future reference.

jase :confused:

[teersy]

Hi all (again),
Well, 2 hrs with the boys at Audi wasn't terribly fruitful, however, has cropped up a couple of leads to follow. They picked up a diagnostic fault - engine coolant sensor - so will price and change that. Other thoughts were breather and vacuum pipes in poor shape. I patched and tidied up a fair bit of pipeage with self vulcanising tape - no change to fault.
If the sensor change fails to help, I'll probably look at the injectors as previously mentioned.
( I've got an 1996 transit van I use for surfing etc - needed a bit of welding for its MOT - wish it were that simple........:()

Jase

[Niall76]

sorry to hear of your continuing problems. Have you tried your local specialist? Where about are you?

[teersy]

HI Niall,
Currently residing in Newquay Cornwall.

Jase

[DaddyA]

Hi Teersy, just been reading your post and it sounds like a problem i had (hesitant A6). Turned out to be the MAF, cars runs fine now. Hope this helps.

[teersy]

Thanks for your help folks.
I've noted all ideas and will crack on this weekend. As usual I'll keep this forum posted for others future reference.
Jase.

[Niall76]

Thanks for your help folks.
I've noted all ideas and will crack on this weekend. As usual I'll keep this forum posted for others future reference.
Jase.

hmmm, I'm wondering if even cleaning out the existing MAF will help. Certainly the cheapest option.

With regards to where you live, I would expect there to be a specialist nearby - well worth a look as these people tend to be much more knowledgeable and helpful - not to mention much cheaper....

[teersy]

Hi all,
Replaced the engine cooler sensor, diagnostic cleared, fault still apparent...ergh...
I'd like to have a go at cleaning the MAF but as I don't have a manual for this motor can anyone explain to me where to find it on the car and if its a fairly easy job?
I also considering going to a garage with a rolling road (mentioned earlier in this thread), I've got a contact for that. With a probable look at the injectors. But, yeah, first of all this MAF, any pointers.

Thanks again,
Jase

[teersy]

Erghhhhh,
Got amongst the MAF last night, cleaned the elements with carb cleaner - sparkling, however, drove the car: no change. I then disconnected the MAF electrically, drove the car, no change/difference. Suspect MAF? The car started no worries with the MAF out of the engine compartment, is that odd? I'd love to try a new MAF in there to test but that ain't gonna happen easy.....
Rolling road session req'd methinks, injector check.........:confused:

Any thoughts/ideas, as usual, appreciated.

:(Jase:(

(reminder of snag: juddering in acceleration, heavy juddering when accel in low gear, low rpm and low speed.)

[lonky]

If engine runs the same without the MAF connected then it is not your issue. Disconnecting the unit causes the ECU to go on a basic settings programme where it does not take into account air temperature volumetrical changes, which is what the unit senses.

[maxlbrown]

I had this problem when just after xmas.

Changed the Coolant temp sensor and MAF no joy. Tested the ht and coil packs and three sets of plugs again no difference

Solved by removing the Air temp sensor in the inlet and cleaning it again this is a £16 part from audi. and always gets overlooked.

In future i will check these first before messing with coil packs and leads and even MAFS:mad:

[teersy]

Thanks again fellas for your advice,
MaxlBrown, I am keen to have a look at this air temp sensor, could you or anyone reading advise me on its location and I'll have a pop at it this weekend.
Would this rear its head on a diagnostic though??
Thanks again.
Jase.

[maxlbrown]

Take off the engine cover at the rear behind the inlet manifold on the top of the engine there is a solid plack pipe on top of this is a sensor held in be torx 35 screw

No 5 on the attached picture

Mine was a bit black rubbed ouff with switch cleaner.

Hope this works (helps) never tried attachemntes before:beerchug:

Mine did not show up on diags either.

[teersy]

Nice one I'm all over it,
I've taken it out and give it and the throttle body a good clean. No difference, however, I tested the sensor for continuity with a multimeter: it showed an open circuit.

Now, I don't know how that sensor works internally/electronically, would it show an open circuit at any point in its operation??

I've got one on order (£30)

Jase.

[maxlbrown]

though your getting an open circuit you should be getting a resistance are you saying your getting no resistance as per the data i snet through. if so then this sounds like your problem.

Good luck.

M:beerchug:

[teersy]

Alas,
No luck with the air temp.sensor. :( Fault remains. So, I've booked in for a diagnostic rolling road session up in Plymouth next week. Fingers crossed. I'll let the forum know as usual for future ref.
Jase.

"If it wasn't for bad luck I'd have no luck at all.!?"

[Niall76]

sorry to hear this is still going on.

I take all rubber hoses which carry air are okay? I have seen in the past ais hoses which look okay but when the engine is under load the split appears due the engine moving on mounts and air being sucked in.

[teersy]

Went to plymouth with the car for a rolling road diagnostic - he came out scratchin' his head. Perhaps injectors he said - get em checked. Took those out, gave them to a company to test - they said although delivery was slightly varied there was a good spray pattern so no snags there. HOWEVER, on going to refit the injectors I noticed some sorry vacuum pipes. They led to the front of the inlet and controlled a rotary device there, quite long item fitted right into the manifold. I replaced the fabric mashed vacuum pipes with thick rubber ones, refitted the injectors and hey presto no more juddering. So, was it down to the hoses or getting the injectors out and perhaps unknowingly doing something there, who knows??????
Beware ******* vacuum hoses.......
Happy now,well after the stereo's fixed (send to OE Electronics) and oil leak sorted (rocker cover gasket), boot central locking (replace locking arm)......etc etc etc
Thanks for all your help - remember this one, it was different........