Car knocking/tapping in Cylinder 3

[HowdyTT]

What I thought to be an ignition coil, may be a bit worse. I was driving and it threw a CEL. CEL started blinking. Car was missing, sputtering. I was close to a PEP boys and had them take a look (mistake, I know).

I call today (a day later) and they said they can't get it started. "It starts and then just dies". I go to the shop, and see the little "key in side the car" icon light thingy to the left of the CEL... I get out of the car, lock it, unlock it, get in and start it. They were amazed by that. Not sure If I just pulled that outta my ass, or was just lucky. It sounds like it's missing, but we hear a knock, or tapping

The mechanic then unhooks each ingnition coil connection to see what happens with the sound. It got much louder with Cylinder 3. He does a pressure test and got 150 (that good? Because this idiot didn't know, he just knew "its not really bad"). The knocking/tapping seems to go away at higher rpm's (or is drowned out by engine noise)

BTW, The initial code for when I brought it in was 2 and 4 were missing.

All spark plugs are black, and can smell gas out the tail pipes.

Now they don't want to touch the car and will have to tow it to Audi tomorrow.

Any idea's anyone?

TIA

[Cincy]

180psi is new, 140psi is the min. So 150 is low, but was this done on a engine that was at temp? If not, then its worthless.

The engine shouldnt have more than 10% diff between the highest cyl and the lowest. Our engines are loud already, so it can be the injectors or lifters. Have them do a complete compression test on the car after you change the plugs and gap them. If its still there, and the compression is good, may want to move to a 50w oil

You may want to check the tb to see if it skipped a tooth if it doesnt come back good after the compression test

[HowdyTT]

180psi is new, 140psi is the min. So 150 is low, but was this done on a engine that was at temp? If not, then its worthless.

The car was running for about 7-10 minutes...

The engine shouldnt have more than 10% diff between the highest cyl and the lowest.

Only tested the one :(

If its still there, and the compression is good, may want to move to a 50w oil

Sorry, I forgot to mention that with the tapping, the car is still missing. So, not sure thicker viscosity would help. At this point, the lazy mechanic gave up and referred me to an Audi Mechanic. I asked if this could still be a plug or coil even though he changed the plugs (Could it?). Shit, I also forget to mention he changed the plugs too, and they still came out black after the 10 min or so idle with the slight rev. In my ignorant (and hopeful) opinion, im hoping it may be still related to spark/timing. Could a tapping noise occur on only one cylinder and be related to coil/spark?

You may want to check the tb to see if it skipped a tooth

Thats a great thought, would/could that produce a tapping in only one cylinder? I should also mention I proactively got the TB replaced 10,000 miles ago (6X,000 now). But I guess that doesn't mean it couldn't be it.


Well, I have one of those used car warranties that covers power train (even though I read horror stories about them). So, I hope worse case they cover it.

What are some possible causes?

-Piston slap?
-Not a spark plug knock sound....
-Injectors?
-Rod?!
-What timing/spark related issues could (if any) produce a tapping noise in only one cylinder?
-If there is a crack in the block, could it keep that 150 PSI in the troubled cylinder?
-???

[Cincy]

Well the car was deff up to temp. So the 150 is plenty low. If its just that one cyl, there has to be severe wear on the walls or valve(s) are messed up. Need to find the cause which means pull the head.

[Murderface]

Wouldn't the cam position sensor bitch if the timing were off?

[exTTreme]

I would have the other cylinders pressure tested before you pull the head.
Check your oil pan for sludge I've always used mobil 1 or royal purple pure synthetic every 3-5k miles in my engine and it still had some sludge which ended up causing oil pump failure which led to bearing failure and a ticking noise

[HowdyTT]

I got a towed back to the place I bought it from. Hopefully know whats up tomorrow, and will hopefull know if my warranty company will cover it

[225ttroadster]

should have pushed your clutch in... make sure it is not making a clutch noise.

Betting the cool pep boys tech did not not do the compression test properly.

Def. should have looked to see if you skipped a tooth. Although an Audi tech friend of mine, told me not to worry about if I as a tooth off when doing my timing job.

[Cincy]

You still need to redo it if your a tooth off. If your more than one off you will damage the head.

[225ttroadster]

You still need to redo it if your a tooth off. If your more than one off you will damage the head.

well I am not lol... he just mentioned not to worry if I was one tooth off either direction.

[Cincy]

the timing position sensor may advise you otherwise

[Murderface]

Yeah lol I've seen threads where people complain that their car is running funny and it's because the timing is a tooth off. It won't damage your motor but it won't run right either.

[HowdyTT]

- Coil Pack
- Injector for Cyl 3
- O-Ring
---------------------
$60 after warranty :)

[Cincy]

Not bad, im sure you couldnt by the o-ring from them for that much

[225ttroadster]

Yeah lol I've seen threads where people complain that their car is running funny and it's because the timing is a tooth off. It won't damage your motor but it won't run right either.

Mine runs fine... Already VAG'd it.. Just trying to figure out the whole n75/MBC thing lol...