To those of you who frequent multiple Audi forums, I apologize in advance for the redundancy. I have posted this question on several forums in hopes of getting maximum feedback.

This is the first time I have ever posted a question on a forum. I am a career lurker, and forums have been of tremendous help to me with other vehicles. I have scoured the Audi forums, and gathered a lot of information, but haven’t really been able to come up with a clear direction for troubleshooting my latest challenge. I am hoping the Audi community will be as helpful as other automotive communities have been, and will give me some guidance.

At 45 years old, I have owned many cars. With the exception of mounting and balancing tires, alignments, exhaust, and machine work, I have done every repair on every car. I have owned foreign and domestic, cars and trucks, and have done repairs as involved as replacing the top end of a Ford Taurus, replacing the transmission on a Ford F150, and replacing the timing belt and steering rack on an Acura RL. I currently have two BMW 3-series, both more than 10 years old. Not trying to pat myself on the back, just giving a point of reference on my level on mechanical aptitude. I like owning and driving older luxury cars. It has worked out well for me, and I have had great success maintaining them at a reasonable cost.

Five days ago I bought a 2002 Audi A6 3.0 Quattro. The guy I bought it from (maybe in his late-20s) got it from his father a couple of years ago. His father was the original owner. The guy gave me all of the maintenance records, and it shows that during the time his father had the car, it was meticulously maintained, and all at the dealership, with the exception of a couple of more recent repairs (serpentine belt, exhaust camshaft at 1,2,3 cylinders, mass air sensor, and coolant temp sensor – all done in January 2013 at a different shop). All routine maintenance was done, all the recall work, plus misc other repairs. When I bought it, the CEL was blinking. The car started fine and ran alright (I have no point of reference, since I have never owned an Audi), but was noticeably rough at idle. I had the codes pulled at Advance Auto Parts before I bought it. It came up with the common misfire codes – P0300, and misfires on all cylinders.

Here are the details of what has happened over the last several days.

Tuesday
Drove the car home, approximately 15 miles. I think the CEL was blinking the whole time.

Wednesday, Thursday
Bought an OBD reader. Pulled codes (the same) and cleared them. Reset the codes, drove around, and pulled codes again. Repeated this cycle a few times. The P0300 and the 4,5,6 cylinders codes seemed to come up first, but they all came back up eventually. Sometime the CEL was off, sometimes it was solid, and sometimes it blinked. I couldn’t identify what variables made the light status change.

Friday
Did compression test. Results were: Cylinders 1,2,3 (passenger side) were all right about 180 psi, cylinders 4,5,6 (driver’s side) were right about 130-135 psi. Spark plugs looked fine when I pulled them, but plugs from cylinders 2 and 3 had oil on them. I already knew that I had an oil leak at the valve cover gasket, so the wet spark plugs were not a big surprise. I also noticed that when I pulled the wire harnesses off of the coil packs, the locking mechanism was broken on many of them, and the screws that secure the harnesses to the engine were missing.

Noticed that a t-fitting near the front of the engine didn’t have a vacuum hose attached to one of the nipples. Found that the hose that should be connected had fallen behind the timing belt housing on the driver’s side. Hose is damaged, so I didn’t try to reconnect. I am going to order new hose and replace it and others. In the meantime, I taped off the open nipple in hopes that it might change something.
I drove it after the compression test and got a new code – P1296. Did the research and determined maybe it’s the coolant temp sensor, although it was just replaced a little over a year ago.

Saturday
Decided that since the compression test came out OK (although I don’t know why there is such a difference side-to-side) that I would pay the sales tax and transfer the title – my commitment to keep the car.

With license plates on it, I decided to put it back on the road. I ran an errand to a location approximately 10 miles from my house. About 4 miles of the trip were on side streets, and the other 6 were on the highway. I actually kept my OBD reader plugged into the car the entire time, so I could continue to check for codes. CEL was blinking most of the trip there. The exception was when I exited the highway. As I was exiting, the CEL went solid, and stayed that way almost the rest of the trip (just a couple of miles). There was also a short time at the beginning of the trip where the light was off.

When I came back to the car, I pulled codes again. Got the misfire codes, but also got P0118 – Engine Coolant Temp Sensor 1 Circuit High. I reset the codes.

I tried to start the car. For the first time, it was reluctant to start. I was able to get it started by flooring the gas. When I let off the gas, it was idling at about 3000 rpm. I tried tapping the gas pedal to see if it would drop the idle, but with no luck. I turned the car off and tried to restart it several times. Sometimes it would start, and then stall, sometimes it would start but idle at high RPM, and sometimes it just didn’t seem to want to start at all.

After multiple attempts, I was able to get it started and get it to idle in the normal range. I (fingers crossed) headed for home. Again, the CEL was blinking most of the way; although a couple of times on the highway it went solid. After I exited the highway, a cycle seemed to start. About every ¼ to ½ mile, the light would change from solid to blinking, then back to solid a ¼ to ½ mile later. The cycle continued the rest of the way home (a few miles).

I got the car home and parked it. Now I’m looking for help. I want to keep the car (cosmetically it is beautiful), and I have the ability and the money (within reason) to repair and maintain it. Anyone have any ideas on what my best next step should be? Thanks in advance for the help!

 

OK, so here's the latest.

After replacing all of the vacuum lines/fittings, the check valve and the coolant temperature sensor (they all needed to be replaced anyway, and I think the breakdown of the vacuum lines/fittings is what caused the car to go from running rough to almost not running at all), I did the leakdown test. I bought a new, US General leakdown tester from Harbor Freight. I have never used a leakdown tester, and due to some wild inconsistencies in readings, I didn't have a ton of faith in the accuracy of the tool or my technique. For this reason, I took as many as 10 readings per cylinder to try to establish trends. Here's what I got:

Cylinder 1 - 30-35% leakage - leaking sound seemed to be coming from the left (other side) head area

Cylinder 2 - 85% leakage - leaking sound was coming from the area where the leakdown tool hose screwed into the spark plug hole

Cylinder 3 - 40% leakage - leaking sound seemed to be coming from the left (other side) head area

Cylinder 4 - 50-60% leakage - leaking sound seemed to be coming from the left (same side) head area

Cylinder 5 - 32-36% leakage - leaking sound seemed to be coming from the left (same side) head area

Cylinder 6 - 22-35% leakage - leaking sound seemed to be coming from the left (same side) head area

Other relevant info:

I removed the upper timing belt covers and both valve covers before doing the testing. I visually inspected the camshafts. One of the lobes on the right exhaust camshaft is noticeably rounder than the rest (the others look great - nice points), but I doubt if it is worn enough to cause all cylinder misfires. Also, this is the camshaft that was just replaced 10,000 miles ago. There is also a worn lobe on the left camshaft, but again, it it just slightly rounded.

With the valve covers removed, obviously I can see the cam followers move up and down. One of the exhaust cam followers spins as it moves up and down. None of the others seem to do that.

At one point in the testing, in an attempt to hear the leaks better, I applied 40 psi of shop air directly to Cylinder 3. I had my socket and breaker bar on the crank nut, and when I moved it back and forth trying to slightly open and close the valves, the cylinder must have sealed and forced the piston down, and it jerked the breaker bar about a 1/4 turn. When I went to move the bar back, it jerked it the other way. Not sure if this could have done any damage.

At one point in the testing, I noticed that as I rotated the crankshaft, the right side camshaft seemed to get hung up temporarily, then sort of pop free. Pop may be an overstatement of the noise/phenomenon, but it stopped briefly, then broke free. I didn't see any obvious place it was getting hung up. It happened at the point just before the exhaust valves at Cylinder 1 opened. I don't think this was happening when I started testing, so I'm wondering if my 40 psi breaker bar experiment may have caused this.

Thanks for listening. I'm all ears, and very anxious for any help you can provide. I'd really like to be driving this car.

 

At the outset let me preface this by saying I dont have the specific answer to your question. I do have some general observations to a new friend to the world of Audi. I currently own 4 audi's that are daily drivers (family) and one old Mercedes, including a 2002 A4 3.0. They range in age for 1997 to 2002. I bought them all used and they all have over 100k on them. There are equal A6's and A4's in the mix and Ive owned a couple of A8's over the years.
1. Every audi I own and have ever owned has the check engine light on. THe CELs have been on for years. At first I "chased the dragon" and spent way to many nights with the VAG reader and far too much money. At this point in my Audi life I have changed my interpretation to "If the CEL light is on in an Audi, That should be interpreted as an indication that the engine is running." Instead of ruining my days with it I now take it as a positive sign. I have switched to the old school method of diagnosis. I listen to the car. I visually inspect the car paying very close attention to the engine and belts. I check for leaks and I drive the suckers. I apply time and money to noises, drips and ugly. I ignore the daily "fresh Hell" that lives within the Audi electronic sensors and dash lights (engine oil, water temp, and gas excepted. My 97 A6 has old school gages and idiot lights and the gages constantly show happiness whenever the idiot sensor lights go into melt down mode.
DIY on an Audi is to be commended, as long as it is accompanied by regular psychotherapy. My audi's are like mustang ponies in the back lot. They look exciting and if you take a ride on one when it is in a pleasant mood can be the ride of your life or you can be thrown off at any time without warning. Its a love/hate relationship in its purest form.
FYI, when the family travels together over long distances we pack into the 25 year old Mercedes and get there and back again every time without a hiccup.
Audi CELs are the lid on Pandoras Box. Abandon hope all ye who enter there.

 

Micwrite, thank you so much for the input. I like your philosophy of "if the CEL is on, then the engine is running." My '99 3-series has an intermittent CEL, and I don't lose any sleep over it. The car runs fine, mpg is good, and I know that it will turn itself back off after a few ignition cycles. If I could get this A6 to that point, I'd be ecstatic. My concern is the rough running and blinking CEL (plus almost not being able to get it started, although I think that was the vacuum issue). I'm happy to do the work necessary to get this A6 back on the road, I just don't want to spend $1000 or more on random parts and "hope" that one of the replaced parts was causing the problem.

 

For leakdown test, I hope you know that the cylinder you're testing should be @ TDC of it's compression stroke (ie. both intake & exhaust valves closed). Glad you didn't get hit by that breaker bar, or it would have likely broke your arm. As you indicated, your movement of the breaker bar on the crank likely seated the valves & pushed piston down. You likely had all other plugs out, which will allow the pressurized cylinder to turn the crank much easier, & faster. I've heard folks using 100 psi for leakdown test, which makes the math easier, just a bit more dangerous if not cautious. You should only turn crank in engine operation direction CW looking aft. If you turned CCW, you may have slacked timing belt temporarily which could cause it to skip a tooth.

I also recently got the HF leakdown tester & checked my son's 2000 A6 2.7 . We only removed plug on tested cylinder that was @ TDC compression. All your leakages seem high for normal levels. So either test done wrong, lots of worn parts, or timing off. I'm not familar with the 3.0L, but for the 2.7, you can check cam to crank timing by removing VCs, turn crank CW (looking aft) to align crank timing mark to ref. arrow. For 2.7, this means #3 cylinder is at TDC of either compression stoke or exhaust. 2 turns of crank per 1 turn of cams. If on # 3 compression stroke, then slot in both intake & exhaust cams (on tensioner side of cam) will align with arrow mark ( ^ ) on cam bearing cap adjacent to tensioner. If slots & ^ marks align for both intake & exhaust cams then the cams are timed correctly. If one or both slots don't align with arrow mark ^ then cam timing is wrong. If cam timing is wrong, then although piston may be at TDC compression, a valve may be partially open, & throw off leakage test. Good luck.

 

I fixed it!

So here's the update, for those who are curious, or to help those in the future, if they happen to have a similar issue.

After compression testing, leak down testing, and visual inspection, I made my diagnosis. There were obvious signs that the last mechanic who worked on this car was sloppy, if not incompetent. Screws were missing from the front bumper and the coil pack wire harnesses, the belly pan was missing, and two of the four plastic engine covers were missing. Also, I noticed white paint marks on the camshaft pulleys. With this information, and knowing how important it is to use the cam lock tool, my diagnosis was that the mechanic who replaced the exhaust camshaft in January 2013 didn't use the camshaft locking tool, and that the timing was slightly off. I pulled the trigger and ordered a camshaft lock tool off of eBay (approx $120 shipped). The tool arrived, and it was time to see if I had guessed right.

The tool went on to the left side fine, but it wouldn't go on to the right side. It went on to the exhaust camshaft, but wouldn't go on to the intake camshaft. It looks like I was right! Time to get the timing belt off.

So I basically did a timing belt service, but had to disassemble the right side without the lock tool on. As soon as I loosened the cam pulley bolts, I rotated the intake camshaft and got the tool to engage. Then I put everything back together. Also cleaned up a lot of oil on the front of the engine. My guess is that the hack mechanic didn't replace the cam pulley seals - but I did.

Moment of truth - time to start the engine. It takes a couple of turns to get fuel back into the engine, but then starts right up. After a few seconds, my wife, who wanted to watch the start up to see if the engine would explode, tells me she thinks the car is on fire. Smoke is coming out from under and behind the car. After initially being startled by the smoke, I realized that I had put oil into some of the cylinders when I was doing testing. I assured her that the car was not on fire, and that the smoke would only be temporary as the oil burned off.

I let the car idle for about 10-15 minutes, then took it for a drive. While not perfectly smooth (I assumed because the computer still needed to fine-tune the timing), it ran well. No CEL.

So now it's five days later. The car runs great! I've been driving it every day, and it's a dream. I was really looking forward to driving this car, and was getting frustrated watching it sit in my driveway while I decided where to spend my time and money troubleshooting it.

Total cost of the repair was about $200, most of which was the cam lock lock tool. Now that it's running well, time for basic maintenance and new RS6 replica wheels!

Thanks to all who gave advice.