Slight misfire after timing belt replacement?
 

Hi all. Picked my new 1999 S8 up a few weeks ago and I'm really impressed with it. It's done a few miles and I was expecting it to have a few knock, rattles etc - but nothing. I bought it on the pretence that it needed a timing belt replacing within a few thousand miles or so.

I got it in to my local garage for the belt, pullies and water pump to be replaced. Picked it up on friday and it seems to have a slight misfire/wobble on idle. I'll be getting it back in to the garage next week but just wanted to see if anyone has had a similar experience or know what it might be as they are not an Audi specilist.

Thanks in advance.

Hi tonyt102,

Welcome to the premier A/S 8 forum and the joy of owning what is a lotta mota for your £.

Ben of AV Performance may be around shortly but I can guess what he may say.

As they weren't a Audi specialist it is unlikely they had the specialist tools for doing a cam belt change. It can be done without them but the chances of error are significantly higher. I would suspect that there is some misalignment in there somewhere which is manifesting itself as a lumpy idle.

Do you have VagCom or does your garage? Check out the error codes.

I see you are up in Cleveland. There may be a forum member that will do a VagCom scan for you nearby.

Read up on the fanbelt change here . Being a 99 it could be a 32 Valve or a 40 Valve. procedure for a 40 valve is different.

Hope you get it sorted.

Check out the A8oc and maube we will see you at one of the events.

Also if you need bits then the forum sponsors are the best suppliers in the UK. A8 Parts.

Thanks for the reply.

I do have the free version of VAG COM so I'll have a look when I get the lead back from my brother. The garage has a Snap On reader so I guess that that should show up any errors.

As for the use of the specialist tools, I'm not sure but I'll ask them about it.

BTW, it is the 40v version.

I'm sure I'll get it sorted.

Cheers.

I haven't used my VAG-COM since I've had my computer with Vista on and it looks like the free version isn't compatable. It's in at the garage tomorrow so we'll have to see. I think I may invest in the proper cable and software.

Well, the garages Snap On code reader didn't bring anything up. They say that many of the vac pipes are perished so I've asked them to thoroughly check/replace them as necessary although I'm not convinced that this is the issue.

Does anyone know if there are timing marks that everything should match up with behind the covers? I asked them today and apparently, they do have the specific timing belt replacement tools.

It's a good call. Leaking breather hoses can effect the idle and they do perish. You can replace the front one with a length of 3/4" radiator hose. the Audi original is 20 to 30 squid. the ones at the back are a bugger to get to and are about £70 the pair.

Yeh, I agree that the breather pipes couple casue idle problems but it's strange that this should occur right after the timing belt change. I can imagine that the vac pipes can become damaged from removal/refitting but I'm not sure about the breather pipes. I really don't know as I've never seen the front end of these engines and I don't know what's disconnected when the belt is replaced. I'm just really worried that the indy I have it at can't sort it and I have to get it to a specialist, doubling the money I've spent.

Thanks for the replies Conan.

Well, had all of the vacuum hoses replaced to no avail.

I have plugged VAG COM in tonight and it brought up no fault codes. I'm quite new to VAG COM so correct me if I'm wrong. I went to the measuring block section with the engine running to get some values for misfiring cylnders and ignition timing. There was no misfires logged although the timing showed between 12-14 degrees BTDC @ 800rpm - is this right as I can find out what it should be? Shouldn't it be 0 degrees or near?

When you say vacuum hoses do you mean crank case breather hoses?

Vacuum hoses effect the variable length intake adjustment.

If your running Vagcom and measuring Blocks 1 , 19 and 20. If you have ant misfires blocks 19 and 20 will record each misfire as it happens. If they stay at zero then no misfires are happening....... I think........ :)

Use the Vag scope facility and record blocks 1 , 19, 20 and post the file as an attachment here. Rev up to about 4k.

Thanks Conan.

I've had the small vacuum hoses replaced as they were all perished - not the breather pipes.

Cheers for the VAG COM tip, I'll try it either tomorrow or Sunday and let you know. Wouldn't it have logged a fault if there was a misfire though?

I have phoned a local VW/Audi specialist (where I should have gone to in the first place). They say that it sound like the cam timing is out which, speaking to a few other people, sounds plausable.

Hi there.
Sounds very much like they havent got the timing belt on correct. On most Audi engines the cam pulleys are mounted on a taper and so have to be loosened from the cams when tensioning the belt. A quick check to see if it's on wrong is pop one of the belt covers off a bit so you can see the cam pulley. If there's a Tip-Ex mark on the cam pulley and the engine then they have definately done it wrong!
As the tension settles it pulls the timing out if they havent set it correctly.

If they have done it right then check a few bits, such as spark plugs, air leaks on inlet and check the inlet manifold hasn't worked it's bolts lose - they like doing that! Also the inlet manifold has change over flaps inside and they can sieze, if during the belt change the guys have moved these then they could have upset it. You should be able to move the 2 change over valves by hand, although the springs are strong, you will get free movement.

Feel free to call me if you need advice: 01283 548 483 (although I'm not at work now!! +++)

Thanks very much for that, I think I now understand the reason for a tapered cam sprocked as opposed to a keyed one. I'm guessing that the cams can be completely locked in place along with the crank (?) then, the belt could be removed, refitted and tensioned without any of the engine moving. This means that no Tip-Ex marks are necessary. Does this sound right?

Like you say, I need to get the cover off to check if they've marked the sprocket and engine. I'll do it tomorrow and report back.

Thanks again.

You have guessed right. Ben has pointed out that with the special tools the cams are locked in place the cam sprockets are loosened so they can rotate and after all the new parts are fitted and the cam belt tensioned. The crank is turned several times to make sure all the tension is taken up. Once this is achieved then it is brought to TDC and the cam sprockets are torqued up while being held in place. The cam locks are removed and all is in sync. +++

Right, got it. I'll report back tomorrow.

Thanks.

Good call Ben. Removed the belt covers today and found that someone has made red timing marks on the cam sprocket and engine. Looks like the job hasn't been done properly. I'll call the garage in the morning and let you know happens.

I'm guessing that everything needs to come apart again, lock the cams, set everything to TDC and tension everything up.

Afraid so - it needs doing again. It should be fine but it's annoying that someone is prepared to undertake a job such as a timing belt replacement on a car like an S8 without arming them selves with the right info and tools!
If you need full instructions and tool list from ELSA let me know.
It'll drive loads better when it's done.

The self created timing marks are the dead give-away! You'd have thought that if the mechanic has to make his own timing marks he would become suspicious of how it's done!!!!!
Never mind, atleast you know what it is and rectification is straight forward.

Thanks for help Ben. I'll let you know how I get on.

No probs at all. Good luck with her! +++

Well the garage were very receptive to my input. I've given them the info from the audipages website as a rough guide as my car is the 40v not 32v. I'm trying to find the relevant tools for the task and there seems to be two very different types; the one on the audipages site (which it explains that the 40v version is slightly different) and this one...

http://www.sealeyonline.co.uk/vs4827...-7-4-2-v8.html

If it's not the one, can anyone recommend one or are they a specific Audi tool?

Thanks.

That's the tool, the Audi number off my one is: T40005. Note though that although this tool LOOKS like the one for the 30v V6 it is different as the V8 is wider.... Must be correct tool. You also need Tool: 3424 the crank locking tool that screws into the block while setting belt.

The belt is pre tensioned with a torque wrench whilst tightenening the cam pulleys too - this is important to asure the belt tensioner can vary itself correctly as the engine temp alters.
They MUST follow ELSA to the letter..... Then it'll run like a dream.

Guys, how can I reduce the size of a word document?? I have copied the instructions from ELSA for this car into a Word doc. but the size limit is 19kb and the doc. is 750kb.......

Thanks again Ben.

Just to confirm, the tool required is in the link I posted, plus the crank tool? They are very different to the 32V one aren't they!

Not sure about the word doc I'm afraid, if it to do with my problem, you can send it directly to my email address if you want, I'll PM it to you.

Thanks again.

All tools req'd VERY different to the 32v!!!! Entirely different valve drive system

I have emailed you the ELSA doc....

Thanks very much for that Ben. I've printed it out and dropped it off at the garage.

I'll let you know what it's like when I get it back.

Cheers.

Just picked the car up and it's all sorted. They ordered the tool yesterday and completely re fitted everything, following the ELSA instructions to the letter.

Thanks to Conan and Ben for your help, especially to Ben for sending the ELSA document.

Cheers guys.

Just need to get it cleaned up and some pictures taken and I'll get it on here.

Antony.

no probs chap.

Glad it sorted! +++