Audi 1.8t misfiring

dmc17

I have a 2000 A4 1.8t quattro and it has been misfiring intermittently. It could run fine for 3-4 days then start misfiring for a few minutes or more sometimes and then go back to running fine again. While idling it drops revs, nearly cuts out and revs itself up to about 1500 rpm and drops back to normal again and can continue this for a while. While driving there is a serious lack of power and it is quite jumpy. Any ideas what could be causing this? Thanks

George Dalton

Could be any number of things with them. Coilpacks give trouble on them but usually when a coilpack fails it just fails outright rather than gives intermittent misfires like you are seeing. First step would be a diagnostic scan and see what the results are before deciding the next step.

franksm

If it does turn out to be coilpacks, it's best to replace all four rather than just the one that has failed.

GSFcarparts.com (they have two shops in Dublin) can supply the right ones, and as far as I can remember from replacing them on an A4 1.8T in the past, it was the Bosch ones they recommended although there were more expensive and also cheaper options in their book.

dmc17

Yeah I must get it hooked up to the computer. Would a problem show up even if it was running fine at the time? The engine management light doesn't come on when it happens.

George Dalton

There is an ongoing recall on some of those coilpacks. It may be worth ringing Audi and checking to see if your car is eligible for free replacements. If it is you may as well get them done. Even if it doesn't solve the problem you will get four coilpacks for free and rule them out as a possible cause.

dmc17

George Dalton wrote: »

There is an ongoing recall on some of those coilpacks. It may be worth ringing Audi and checking to see if your car is eligible for free replacements. If it is you may as well get them done. Even if it doesn't solve the problem you will get four coilpacks for free and rule them out as a possible cause.

That's worth a shot. Thanks

George Dalton

Is the misfire mainly present at idle and low engine speeds? How does the engine perform when the car is on the road?

EDIT: Sorry just re-read your first post where you answer my question!

Where are you located?

dmc17

George Dalton wrote: »

Is the misfire mainly present at idle and low engine speeds? How does the engine perform when the car is on the road?

The cars runs fine most of the time. When it starts misfiring, while driving it loses power and gets jumpy. If you stop and let it idle it tries to cut out and then revs it self up and continues to do this. It can run perfect for days at a time and then only do this at random times. Its driving me mad I'm in Clare

George Dalton

As I said there are a few common issues on the 1.8T that can cause those symptoms. If you don't have any success with the new coilpacks then report back here and we will try to help you out.

dmc17

George Dalton wrote: »

As I said there are a few common issues on the 1.8T that can cause those symptoms. If you don't have any success with the new coilpacks then report back here and we will try to help you out.

Will do. Thanks for your time

billy few mates

I didn't know you had to replace coilpacks as a set.....

My son had a faulty one on his last car (symptoms very like yours except he also go an engine management light) and the mechanic replaced just the faulty one and it worked perfectly again....

dmc17

billy few mates wrote: »

I didn't know you had to replace coilpacks as a set.....

My son had a faulty one on his last car (symptoms very like yours except he also go an engine management light) and the mechanic replaced just the faulty one and it worked perfectly again....

I suppose if one goes, chances are the other three aren't far behind

George Dalton

You don't have to replace them as a set. You can just replace the faulty part and leave the others. But when Audi are offering four new ones for free would you say no? :pac:

dmc17

George Dalton wrote: »

You don't have to replace them as a set. You can just replace the faulty part and leave the others. But when if Audi are offering four new ones for free would you say no? :pac:

franksm

As the lads say, it's not compulsory to replace all four, but I had a 2nd one go 3 weeks after replacing the initial one. So to be 110% sure, I ended up renewing them all.

If you have a code-reader, it's easy to see which one of the four has failed.

My check-engine light wasn't lighting up all the time when the car was misfiring. If the car misfired under load or sometimes at idle, the lamp would only light after the car had been running for 15 mins or more.

I used this cheap code-reader to read the codes, even when the lamp was extinguished:

http://www.ebay.co.uk/itm/221040985066

14 quid Sterling !

Moanin

dmc17 wrote: »

I have a 2000 A4 1.8t quattro and it has been misfiring intermittently. It could run fine for 3-4 days then start misfiring for a few minutes or more sometimes and then go back to running fine again. While idling it drops revs, nearly cuts out and revs itself up to about 1500 rpm and drops back to normal again and can continue this for a while. While driving there is a serious lack of power and it is quite jumpy. Any ideas what could be causing this? Thanks

Did you try cleaning the throttle body? A dirty one can cause that erratic revving.

dmc17

Moanin wrote: »

Did you try cleaning the throttle body? A dirty one can cause that erratic revving.

Yeah i had the plugs changed and throttle body cleaned but it still happens

dmc17

Well I rang Audi and no new coil packs for me
However it came up with fault code 00561 when connected to computer which I assume means I don't need coil packs.
These are the symptoms I'm getting http://wiki.ross-tech.com/wiki/index.php/00561
Where do I start

firefly08

I'm no expert but I think what the code is saying is that it's running too lean or too rich - in other words the computer is not getting the correct info regarding how much air is coming into the engine, or the injectors are not giving the amount of fuel they're supposed to. The list of solutions given are just the most typical causes of that scenario. None of those possible causes should involve replacing expensive parts on speculation, so don't accept a garage just selling you stuff without diagnosing the problem.

Fuel pressure can be measured by just hooking up a gauge to the rail. If fuel pressure is wrong, then might be the regulator, filter or pump.

To check for vacuum leaks, there are various ways but probably the handiest is to pressurize the intake and try to find air leaking out. It could be as simple as tightening a hose clamp or replacing a hose.

To check the MAF, I think the vag-com software can do that (?). It can also be cleaned but I doubt that is your whole problem.

To check the injectors, you can visually check that they're seated properly, check electrical connections are ok, and beyond that I think they should be sent to a specialist. They can check the flow rates precisely and clean/re-seal the injectors. You could put some injector cleaner in the fuel but if they're bad enough to cause your issue I would want them professionally cleaned.

I would leave the injectors until last.