2003 Audi A4 3.0L issues. CEL. P0421 w/ engine symptoms. Time for new coil packs?

[BigKD]

First post here. Please forgive me in advance as I am pretty incompetent when it comes to cars! I have a 2003 Audi A4 3.0L with 127k miles.

Recent history:


Last summer: Turn signals started going bonkers. Had it in the shop several times, and the problem always came right back. Last time they said I need a new turn signal module maybe? but could not find part. I said screw it. A week later the windshield wiper fluid stops spraying. Fuse is blown. Replacing fuse fixes problem but the fuse blows quickly again. Strangely, the turn signal problem has more or less corrected itself over the cooler months but wiper fluid issue remains.

Two months ago: Check engine light came on with no obvious symptoms. Then I noticed that the car had some episodes of needing to turn over longer than uusal in order to start. Had the battery checked at auto zone, and it was fine. Check engine light code was for the catalytic converter/O2 sensors.

Took car to shop last week, as I noticed RPM "surges" when accelerating at sub 2k RPM range. Idle may be somewhat rough. Shop "fixes" windshield wiper issue with new fuse. Oil change, tires rotated, new spark plugs, and a new coolant temp sensor. Catalytic converter tested fine so no new O2 sensors, and they cleared the engine CEL.
Windshield wiper fluid works one time and then dies as I leave shop parking lot, lol. Engine "surge" issue is not fixed and CEL returns about 20 miles later. Car now shudders a bit when accelerating from low speeds/dead stop. Engine seems good as new at 2k+ rpms.


Sound like a coil pack problem? Makes sense to my novice brain. Engine misfires, fuel makes its way into catalytic converter, and the CEL with P0421 code appears.

Any ideas for the turn signals and wiper fluid issues?

[JustinM]

What's the symptoms of the turn signals!?

If they are just acting up and sometimes saying they are out but then working sometimes, then it's possible that you need to take the turn signal out and use a small pick to slightly bend out the metal tabs so they can get better contact. Do it on the headlamp side as well, if possible.


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[[RS4]fsu16a]

Just had the same car and I would say just get rid of it! Once it got over 130 it seemed like the car just fell apart! Issue after issue with car!

[SlickFix]

For an issue like this, there should be a code being thrown. Can you have it scanned again? Btw, I have the same year car and same engine, and I also have the same P0421 code off and on. I haven't been able to determine whether the catalytic converters are going bad, or whether it's the sensor.

Anyhoo, for the rough idle and RPM surges, I'm thinking vacuum leak. With that many miles, if the original vacuum lines haven't been replaced yet, you could easily have a vacuum leak.

What kind of shop are you taking it to? I think you need to find a good independent Audi mechanic if possible. It sounds like the shop you're currently using is not the sharpest knife in the drawer.

[BigKD]

What's the symptoms of the turn signals!?

If they are just acting up and sometimes saying they are out but then working sometimes, then it's possible that you need to take the turn signal out and use a small pick to slightly bend out the metal tabs so they can get better contact. Do it on the headlamp side as well, if possible.


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The symptoms are hitting the left turn signal and the having the right signal go off and vice versa. Sometimes it would alternate between left/right, and other times it would just really not work at all. I'm assuming the shop was doing exactly what you said when they were opening up the turn signal and trying to improve the contacts.

Just had the same car and I would say just get rid of it! Once it got over 130 it seemed like the car just fell apart! Issue after issue with car!

Definitely considering dumping it. It was purchased for $20,000 with 10,000 miles on it...so it has been a pretty good overall value.

For an issue like this, there should be a code being thrown. Can you have it scanned again? Btw, I have the same year car and same engine, and I also have the same P0421 code off and on. I haven't been able to determine whether the catalytic converters are going bad, or whether it's the sensor.

Anyhoo, for the rough idle and RPM surges, I'm thinking vacuum leak. With that many miles, if the original vacuum lines haven't been replaced yet, you could easily have a vacuum leak.

What kind of shop are you taking it to? I think you need to find a good independent Audi mechanic if possible. It sounds like the shop you're currently using is not the sharpest knife in the drawer.

I took it to these guys last week: https://plus.google.com/102318514473...20/about?hl=en

Not sure about the vacuum leaks, but it is still interesting to note that there are no issues above the 1.5k rpm range.

I just had it hooked up again today at Auto Zone and it was the P0421 code.

[BigKD]

Looks like I qualify for the coil recall! Taking it in to the local dealer next week. I'll report back if it fixes the problem or not...

[nazisled]

doesn't the CEL flash repeatedly when there's a cylinder misfire? i don't think it's a coil pack. your car feels like it's falling apart when driving with a bad coil pack.

however, it sounds like clogged cat. pretty soon it probably won't start. i had this experience on my first car. had to tap it with a hammer to start it up lol.

[BigKD]

doesn't the CEL flash repeatedly when there's a cylinder misfire? i don't think it's a coil pack. your car feels like it's falling apart when driving with a bad coil pack.

however, it sounds like clogged cat. pretty soon it probably won't start. i had this experience on my first car. had to tap it with a hammer to start it up lol.

So if the cat. converter is "clogged" do you have to replace it? Because I think that may be expensive to the point that it's not worth fixing on this car. It's probably only worth $5,000 at this point. But I live in SC [no emissions checks] so I guess they could just yank the converter out, and I would be ok?

As I said earlier, the shop tested the cat. converter and said it was fine. Maybe they're wrong?

[brady.]

like slickfix said, it could be vacuum leaks.

if your symptoms still exist after replacing coil packs check out vacuum leaks. plenty of threads here that go further in depth. once doing this you should also check all your plastic t fittings, plastic check valves, plastic everything in the "vacuum system." it may be a wild goose chase and a vacuum leak is not the issue at all... but to be honest at 130,000 and oem vacuum lines? its time to refresh them. <--- also I suggest you do this yourself. all the resources are here and its much cheaper than a shop

as for the cats, as soon as mine go I am investing in a new exhaust. the oem cats are not known for reliability. some go at 100,000. some go at 160,000. typical rule of thumb is 120,000 for the 3.0s. I am at 140,000 and running strong (question mark? ... just waiting for it to go, then new exhaust baby).

*there is not much out there for our 3.0s but same concept as the 1.8t without turbo :), this thread is a good start.

[SlickFix]

I made a DIY on replacing all the vacuum lines in a 3.0. It's a lot of "fun", but well worth it.

[brady.]

I made a DIY on replacing all the vacuum lines in a 3.0. It's a lot of "fun", but well worth it.

oooh yaah... I forgot about this . also a very good write up ^

[BigKD]

So the new coil packs are in. Engine feels smoother overall, but the engine symptoms still remain. Audi dealer said that a bad cat converter can cause the ECM to control the engine in weird ways causing symptoms. OEM converter is 1700, but they said I might be able to get an Indy muffler shop to weld in a universal converter for much less money.

[SlickFix]

So the dealer recommended a new cat without investigating anything else? I encourage you to have the vacuum lines inspected before you plunk down $1700 on a new cat.

[imnuts]

Just had the same car and I would say just get rid of it! Once it got over 130 it seemed like the car just fell apart! Issue after issue with car!

I'm at 161k miles now and have had relatively few issues with my 3.0 to date. Keep up on the maintenance, and it can last well over 200k miles. I even purchased mine used with an unknown service history and it's done well for me. I have spent a considerable amount though in the past two years going through and replacing a lot of various items though as the years and mileage have taken their toll, but my car is still doing fairly well considering it's >10 years old and has a ton of miles on it.

As for the symptoms and possible causes. If the coil packs were the problem you'd get a code for a cylinder misfire. No codes for that, so it isn't the issue, though it's good you got them replaced under the recall anyway. A few other things to check, as was stated, check the vacuum lines. Also, something that could cause odd issues from what I've read is a clogged PCV system. I believe that mine is clogged and get random times of sluggish performance and occasional random misfires. If you go through and check/replace both the vacuum lines and PCV system and it's still having problems, then it could very well be a partially collapsed catalytic converter. If you go the route of replacing it with an aftermarket/universal replacement though, you may not get rid of the CEL code for it.

[brady.]

I still say do vacuum system refresh first considering its cheap and easy. but afterwards... hfc exhaust would resolve those issues yes? <-- if it truely is a cat issue. would throw no cel either. price wise I would guess $700-$1500 depending upon budget and connections. plus you get a whole exhaust.

to be honest it depends how much "you want to get into cars." all cars are so much cheaper if you do the repairs yourself. as soon as you step into a dealer / shop / etc. price shoots up. and audi parts in general are pretty hefty. none of these suggestions we are saying is the definite answer. you could be on a wild goose chase for a long time before you find the answer.



so if you decide yes, buy rosstech vagcom and bentley owner manual. between audizine, vagcom, and the bentley everything can be fixed.

[BigKD]

I still say do vacuum system refresh first considering its cheap and easy. but afterwards... hfc exhaust would resolve those issues yes? <-- if it truely is a cat issue. would throw no cel either. price wise I would guess $700-$1500 depending upon budget and connections. plus you get a whole exhaust.

to be honest it depends how much "you want to get into cars." all cars are so much cheaper if you do the repairs yourself. as soon as you step into a dealer / shop / etc. price shoots up. and audi parts in general are pretty hefty. none of these suggestions we are saying is the definite answer. you could be on a wild goose chase for a long time before you find the answer.



so if you decide yes, buy rosstech vagcom and bentley owner manual. between audizine, vagcom, and the bentley everything can be fixed.

I might be able to handle the vacuum system refresh as I use to cut tubes and seal vacuum lines in a research chemistry lab. Trouble bubble to find issues etc.

1700 for the cat ain't happening. No way. Car is only worth 4k at this point. I don't care about clearing the CEL, but I do care about getting rid of the weird engine symptoms before it stresses and breaks something else and I have more problems on my hand.

[BigKD]

So when y'all say that it is easy to swap the vacuum lines...do you mean easy for someone familiar with working on cars or easy for anybody with average technical aptitude?

I'd really hate to hack away at those lines, make a mistake, and end up with the car in worse shape.

What would happen if you end up with a significant loss of vacuum due to a poor vacuum line installation job?

Also, do y'all use vacuum grease at all at the hose/nipple junction? Seems like it might help ensure that you have a good seal and also help the tube slide into place.

[SlickFix]

It's definitely a doable job for someone who is patient and careful, regardless of previous experience. If you follow my DIY I posted above, I show you the proper technique. To prevent breakage of some of the more brittle plastic tubes and nipples, you slice the old lines and peel them off, instead of trying to pull them off. For inserting the new silicone lines onto the nipples, a little dab of dish soap works great.

If you don't feel up to doing it yourself, by all means take it to a reputable Independent Audi mechanic. Worse case, there's always the dealership(be prepared to open your wallet, though.)

This is precisely why people on AZ make these DIY's, for people like you and me who are not trained mechanics, but want to try our hand at keeping the car in good shape. I'm an IT guy, and fly a computer all day. I love getting my hands greasy and rolling in fluids on the weekend.

[BigKD]

Alright guys, I snapped some pics of my vacuum lines. The rear lines look like they are in decent shape, but these front lines...lol. Looking pretty frayed.

[SlickFix]

Oh dear, those are about 50k miles past due for replacement.

Btw, it looks like you also need to tighten that power steering hose clamp in your second picture. It appears to be leaking.

[BigKD]

Oh dear, those are about 50k past due for replacement.

Btw, it looks like you also need to tighten that power steering hose clamp in your second picture. It appears to be leaking.

Look close enough and you are probably going to find all kinds of things that need help, lol.

Where did you get those plastic T's for the refreshed vacuum lines in your tutorial?

[SlickFix]

Look close enough and you are probably going to find all kinds of things that need help, lol.

Where did you get those plastic T's for the refreshed vacuum lines in your tutorial?

Well, I also noticed the line running down the middle of your serpentine belt, but I figured why pile on.


I got a nice little box of plastic tees from the local Fleet Farm store for $5. My local Audi stealership wanted $6 for one tee!

[BigKD]

Well, I also noticed the line running down the middle of your serpentine belt, but I figured why pile on.


I got a nice little box of plastic tees from the local Fleet Farm store for $5. My local Audi stealership wanted $6 for one tee!

Fleet farm? Ain't got those down here. How about Auto Zone?

[SlickFix]

Sure, but I'd probably call around to see which stores have them. Fleet Farm is an upper Mid-West store in the same vein as Menards/Lowes/Home Depot, but they also sell things for the farm.

[john_gonzo]

Fleet farm?

http://www.youtube.com/watch?feature...JLKvE2Gc#t=35s

[BigKD]

Welp, I just ordered 20 feet of vacuum tubing listed in the DIY thread. I'm going to start with the front vacuum lines that look terrible and easy to fix. Hopefully I notice an improvement. Also if I run into problems is there like an audizine emergency hotline? lol

[BigKD]

SlickFix: what size plastic "T's" do I need for this job?

[john_gonzo]

what size plastic "T's" do I need for this job?

5/32" TEEs. Of course if none break, then none needed. Best way to save the old fittings is explained in the SlickFix DIY (link above). A utility razor also works well for slitting the old hoses.

Starting on the front hoses is a good approach, but don't be surprised if your engine runs the same at low rpms after the new hoses are installed. Here's why:
http://www.audizine.com/forum/showth...=1#post3407948

[BigKD]

5/32" TEEs. Of course if none break, then none needed. Best way to save the old fittings is explained in the SlickFix DIY (link above). A utility razor also works well for slitting the old hoses.

Starting on the front hoses is a good approach, but don't be surprised if your engine runs the same at low rpms after the new hoses are installed. Here's why:
http://www.audizine.com/forum/showth...=1#post3407948

Thanks for the "T' size BTW. I'll try to salvage what I can, but I would feel better having all new parts in there.

EDIT: Link makes more sense after reading the OP. I just checked my engine and those changeover valves are definitely open at idle. Is this definitely abnormal?

[john_gonzo]

I just checked my engine and those changeover valves are definitely open at idle. Is this definitely abnormal?

Not sure I understand "open at idle". Your second pic in post #19 shows the two actuator arms in the correct position for an idling engine. At ~4200 rpm, vacuum is applied to the bulbs and both the arms retract and rotate the changeover valve. Does that make sense?

[BigKD]

Not sure I understand "open at idle". Your second pic in post #19 shows the two actuator arms in the correct position for an idling engine. At ~4200 rpm, vacuum is applied to the bulbs and both the arms retract and rotate the changeover valve. Does that make sense?

What you see in the pic is with the engine turned off. When I start the car and idle in park...they change to the other position

[BigKD]

6/6 front vacuum lines are replaced. Had a hell of a time with one of them and ended up ripping out an additional 12 inches of brittle plastic line.

Problem still exists at low rpms, but netween the coil packs and the vac lines it does not seem as noticeable. Could be all in my head, though.

Tomorrow I tackle the rear vac lines. If the problem still persists, should I get my O2 sensors replaced? The shop last week said that my catalytic converter tested out fine.

[BigKD]

I still say do vacuum system refresh first considering its cheap and easy. but afterwards... hfc exhaust would resolve those issues yes? <-- if it truely is a cat issue. would throw no cel either. price wise I would guess $700-$1500 depending upon budget and connections. plus you get a whole exhaust.

to be honest it depends how much "you want to get into cars." all cars are so much cheaper if you do the repairs yourself. as soon as you step into a dealer / shop / etc. price shoots up. and audi parts in general are pretty hefty. none of these suggestions we are saying is the definite answer. you could be on a wild goose chase for a long time before you find the answer.



so if you decide yes, buy rosstech vagcom and bentley owner manual. between audizine, vagcom, and the bentley everything can be fixed.

What is an hfc exhaust?




...Please forgive my newb status!

[BigKD]

Welp...all vacuum lines are replaced. What a major PITA. And the symptoms along with the CEL still remain. I guess it's good to cross that possibility off the list, though. Some of those vacuum lines were in terrible shape!

[brady.]

your check valves, N49, bla bla bla <-- sorry I do not have all these memorized. Could be cracked too, any and all plastic parts involved with the vacuum line system is suspect. Also the bigger Y vacuum line that is the "source for the vacuum", its connected to the intake manifold, towards back of engine, could be bad. Turn your engine on and listen if you hear hissing. Try and pin point it. If it is big enough you can hear it with just your ears.

could be your intake manifold / intake runner may be broken. mine was and ended up needing to be replaced. read my random misfire thread, you can find by clicking on my name then threads I posted.

questions ask :)

[BigKD]

your check valves, N49, bla bla bla <-- sorry I do not have all these memorized. Could be cracked too, any and all plastic parts involved with the vacuum line system is suspect. Also the bigger Y vacuum line that is the "source for the vacuum", its connected to the intake manifold, towards back of engine, could be bad. Turn your engine on and listen if you hear hissing. Try and pin point it. If it is big enough you can hear it with just your ears.

could be your intake manifold / intake runner may be broken. mine was and ended up needing to be replaced. read my random misfire thread, you can find by clicking on my name then threads I posted.

questions ask :)

Oh trust me...after observing the amount of brittle plastic shit in this engine for the past two days...I would not be the least bit surprised if some plastic connection was crumbled to nothing.

I will say that when I sliced open the old vac lines...I could hear the vacuum being let out. So that would point to the connections at the vacuum source being in working order

[brady.]

What is an hfc exhaust?
...Please forgive my newb status!

high flow cat converter. the oem ones are so restrictive and not to mention unreliable. for the 3.0s cats go from 100,000 to 130,000. (this is a conservative guesstimate, lots of people say 120,000 to 140,000). in anycase, higher flow doesn't "choke" the engine as much. installing a hfc barely sees engine performance increase with 3.0s but still... healthier for the car. environment? not so much. still good enough to pass emission laws in say cali though.


dude... I am just as much of a noob as you. If I have a problem, I google the symptoms (literally). thats how I have learned so much about computers, and now I am starting to build this foundation for my car / audis. *thumbs up*

*I have been researching these cars for only about 6 months now. wow! doesn't feel like that. feels like I just picked up my A4 yesterday. man I felt old for a brief second there, haha.

Oh trust me...after observing the amount of brittle plastic shit in this engine for the past two days...I would not be the least bit surprised if some plastic connection was crumbled to nothing.

I will say that when I sliced open the old vac lines...I could hear the vacuum being let out. So that would point to the connections at the vacuum source being in working order

to be honest I don't know if you hearing pressure confirms the parts healthy. I am confused as to why you hear pressure because I would think since the engine is off... "vacuum off." Engine on, vacuum is created, thus vacuum lines, "vacuum on." <--- someone else needs to pitch in here because this is just me trying to connect dots.

[SlickFix]

The good news is that while it may not have completely solved your current problem, it has resolved - in advance - a vacuum leak that was sure to happen.

And now you've got some groovy looking blue silicon hose in your engine bay to admire.

Btw, when you had the breather hose ends off, did you notice whether or not they were clogged with crud?

Has the PCV valve ever been changed? The whole breather systems(consisting of the PCV valve and some hoses) would be another on your list of things to replace. And if you thought the vacuum lines were a PITA, wait til you try to replace that rear breather hose that connects from the bottom of the PCV valve to the engine block...in the rear of the engine below the throttle body. So far, that is the only job where I truly wanted to firebomb my Avant.

[BigKD]

high flow cat converter. the oem ones are so restrictive and not to mention unreliable. for the 3.0s cats go from 100,000 to 130,000. (this is a conservative guesstimate, lots of people say 120,000 to 140,000). in anycase, higher flow doesn't "choke" the engine as much. installing a hfc barely sees engine performance increase with 3.0s but still... healthier for the car. environment? not so much. still good enough to pass emission laws in say cali though.


dude... I am just as much of a noob as you. If I have a problem, I google the symptoms (literally). thats how I have learned so much about computers, and now I am starting to build this foundation for my car / audis. *thumbs up*

*I have been researching these cars for only about 6 months now. wow! doesn't feel like that. feels like I just picked up my A4 yesterday. man I felt old for a brief second there, haha.



to be honest I don't know if you hearing pressure confirms the parts healthy. I am confused as to why you hear pressure because I would think since the engine is off... "vacuum off." Engine on, vacuum is created, thus vacuum lines, "vacuum on." <--- someone else needs to pitch in here because this is just me trying to connect dots.

I don't know if cars work this way, but when I used to work on gas manifolds in a chemistry lab, we would turn off the vacuum pumps...and if the manifold and vac lines were leak free, the system would hold a tight vacuum [25-30 mmHg] overnight. The sound that you hear when breaking the vacuum seal is all of the atmospheric gas molecules rushing in to fill the vacuum and reach equilibrium.


Slickfix:

When I had the breather hose off, it looked nice and clean. I also managed to crack off one of those tabs, but since it was still next to impossible to remove the breather tube with the 3 remaining tabs, I'm not too worried about it atm.


I have no idea if the PCV valve has ever been changed. My father owned the car from 10k to 120k, and I know it had regular service at 100k miles, which included a new timing belt.
And yea...lookin' sexy in there with the new blue tubing!