Misfire on cylinder three?

Hi,

Yes, a failed spark plug can cause a misfire. Are these original spark plugs, or have they been replaced? If they are original, I would replace all of them. I don't know if you need them, but I attached the directions below.

Also, keep in mind there could be other causes. For example, a faulty fuel injector or there may be no power to the coil. Have you checked those things as well?

Let me know.

Joe

See pics below.

Have not checked the power to coil. What are the wires supposed to have with ignition on? Injectors last thing i will check as its labor intensive.

And counting cylinder from passenger side am guessing to the right is where cylinder 1 starts.

Switched plugs same thing. Compression 30 while next cylinder is 120. Darn. Car only has 104,000. Is it possible something under the valve cover can tell me if a valve is bad? Could carbon build up prevent a valve from closing properly?

Hi,

Which cylinder only has 30 psi compression? As far as carbon, it is something that is possible. For compression to be that low is really odd with this many miles.

I know these vehicles are known to have timing chains that stretch. It could be an issue, but that is really off.

Let me know what the readings were from each cylinder. Also, you may want to remove the valve cover to see if the chain is loose.

Let me know.

Joe

Cyl 3. My understanding is that if its carbon usually it will misfire when cold only, unless its severe. Also, is there possibility of a wash? Ya if its timing it would either make a chain noise at least or throw codes, bit neither are present. Car is super clean. And usually there would be misfire on more than one cylindert olus can or crank codes.

I read online that if you put a bit of oil and recheck, if the compression changes its a ring/piston issue, if it doesn't it's in the head or sticky lifter. Mine didn't change, so crossing fingers. When u rev it up pass the misfire range its so smooth. Even if left idling with the misfire also smooth no funny noises. Would you remove the intake abd look at the valves and build uo first or remove the valve cover first? I also looked at the piston and looks normal

Hi,

That is correct. You can perform a wet compression test which indicates if it is a ring issue. However, at 30 psi, I didn't feel the rings were the issue. That's why I didn't recommend it.

At this point, the only thing we can do is remove the valve cover to see if there is anything that obviously stands out. If you still have 30 psi, a valve would have to be nearly closed because if was excessively open, you would have 0 compression. Also, there is a chance (slim) that the head gasket has failed.

Also, although you don't feel the misfire at a higher RPM is simply because of the engine speed. At 30 psi, the misfire is still there. It just can't be noticed.

Let me know your thoughts or if you have other questions.

Take care,

Joe

Not seeing anything strange or different here. This was a PITA to remove.

If you check the cylinder 3 valves, do they appear to be fully closing? You may have to turn it by hand a bit.

Also, nothing is easy on an Audi. LOL I always say the first step to any engine repair or service is "remove engine."

Let me know.

Joe

I don't want to turn the cams while they are not bolted now, that calls for a disaster if anything jumps as far as the chain goes. Let me check and see if they closed.

Can't really tell if they are or not.

Hi,

Is it possible for you to get a clearer image with the borescope? I couldn't make out things too well.

If you can't get a better pic or tell if the valves are closed, other than removing the cylinder head for inspection, there isn't much we can do.

Let me know your thoughts. Also, let me know what I can do to help.

Take care,

Joe

Removed intake. Geez the carbon build up. All intake mantild runners move like they should. Not seeing any damage to aby valve ir broken pieces.

And this silly design where i must out back the valve cover if i want to spin the motor cause the valve cover bolts hold down the springs. Can you get me the torque specs for these torx bolts?

Hi,

Wow, that is a lot. Now that I see that, I suspect we may have a valve not fully seated. Are you able to get it cleaned out at all?

As far as the torque specifications, I added them below. Make sure you follow them in the three-step process indicated. Also, don't overtighten them. Make sure the surfaces are clean and dry before installing the sealant.

Let me know if this is what you needed.

Take care,

Joe

See pics below.

So, how do they expect one to turn the motor if needed and if one wants to see the cams while turning? Crazy design. Yes, i have cleaned carbon on Audis before, i have the tools.

Hi,

That's a good question. LOL Install the cover, turn the crank to TDC, and remove the cover to see. If it isn't aligned, install the cover, turn the crank 360 degrees, and check again.

Honestly, I don't know who comes up with these designs. I have an old one, 2005 3.0L. It's a lot easier to work on.

Joe

Not removing it again lol. Installed it and placed valves of cylinder 3 TDC and put in some b-12 until the walnut grains come in. Hopefully no major issues. I don't see the bent anywhere so hopefully it's just that.

Hi,

I wouldn't want to remove it again either. What a nightmare. LOL Years back, I had a beautiful A8. It developed a coolant leak at the oil cooler. A 3" plastic pipe with o-rings on each end needed to be replaced. I think the parts were under 20.00.

Step 1 in the manual was, to remove the engine. Ugh!!! LOL Well, I'm too stubborn to do that, so I worked around that and did it in 3 hours. Just FYI, the manual called for 24 hours of labor which included the removal of the "liquid-cooled alternator." Yes, 24 hours.

When they break, they can be a headache. But when they are right, nothing drives nicer.

Let me know how things work out for you.

Take care,

Joe

Hi:

I wouldn't want to remove it again either. What a nightmare. LOL Years back, I had a beautiful A8. It developed a coolant leak at the oil cooler. A 3" plastic pipe with o-rings on each end needed to be replaced. I think the parts were under 20.00.

Step 1 in the manual was, to remove the engine. Ugh!!! LOL Well, I'm too stubborn to do that, so I worked around that and did it in 3 hours. Just FYI, the manual called for 24 hours of labor which included the removal of the "liquid-cooled alternator." Yes, 24 hours.

When they break, they can be a headache. But when they are right, nothing drives nicer.

Let me know how things work out for you.

Take care,

Joe

Wow. I believe it. I had same scenario for a an 02 wagon i think it was a v8 mechanic ended up removing engine for a coolant hose, could be the same hose.

Ugh. Same results after valve fleaning. Possible exhaust side?

Hi,

Certainly, it could be. Have you checked to see if there is any change in compression?

Let me know.

Joe

Not yet.

Measured, still around 30.

I took a few pictures, does this look like a bent valve or is this normal? Not sure if the cylinders usually have groves on these engines.

Hi,

Are the pics you attached all from the same cylinder? I do see marks in picture number two, but pics 1 and 3 don't appear to have the same marks. Also, if there was interference between the valves and pistons, you would know. The pistons would have a clean mark where they touched.

The idea that you may have a bent valve really isn't shown in these pics. Remember, since you have 30 psi compression, which indicates there isn't a bent/stuck open valve. Based on that information, I would suspect something is preventing one of the valves from fully closing.

Let me know.

joe

Yes, all from same piston 3, one was a side picture to show valve. Strange problem to tackle.

Is it pic 1 that shows the valves? If so, they don't look seated properly. I may be wrong because it's difficult to tell in a picture, but is what I see.

Let me know.

Joe

Yes, that's what I am seeing. Do exhaust valves usually suffer from carbon build up as well?

The only thing that scares me when removing the head is the chain. I don't want to deal with timing as i know I am not so good at it. So, i don't want to remove the chain completely but rather just hang it on each side. Also, i see some people remove the turbo aside some don't so i don't know which is easier in this case, whether to leave it on car or remove it with the cylinder head.

Hi, 43

Either valve can have a carbon issue. If you check other cylinders, do they look the same?

As far as the timing is concerned, I totally understand. This vehicle will require special tooling to hold the cams in place. I attached the directions for camshaft timing chain removal and installation so you can see what needs to be done.

Let me know if this helps.

Joe

See pics below.

Thanks. All valves had build up which i walnut blasted. Still same exact compression of 30 on that cylinder. No knocking, no timing codes. Ya the chain is scary, i have seen people remove the sprockets and hood the chain to each side tight till done, but not sure if it's doable. One mistake and it's done. I have all of these tools pretty much. Not sure if the issue could be on the exhaust side or if build up can happen there like it does on intake side.

It could be either side. If you decide to remove the head, let me know. I'll try my best to help from here. Also, as long as the colored links on the chain are aligned with the marks, it will be in time. Once reassembled, you can rotate it by hand to make sure there is no interference.

Let me know if I can help.

Joe

Yes, I do not like the timing chains on Audis, done it before on VW's and it was ridiculous. I will see what i decide to do with it cause it's a clean car with good miles and I don't want to spend $2,500 on a motor. Would you remove the turbo/exhaust manifold to the side at this point to look at valves if it was you?

Hi,

If you plan to remove the cylinder head, I wouldn't. If, however, you don't want to remove the head, then yes, I would likely remove it for inspection.

And yes, the timing is a nightmare. Hang in there.

Joe