Cylinder misfire help

[HopskinsS4]

Ok so here's my problem last week when driving the car after getting on it, it seemed to fall on its face a little bit. So after a couples days it got worse all the way down to a rough idle. I ran the code and it said bank 2 running lean. So I repaired a few old vacuum hoses and replaced the fuel filter. It still continues to have a rough idle and now it's throwing a code for cylinder one misfire P0301. I changed the coilpacks around and spark plugs and it still is saying cylinder one misfire. The car now has a rough idle and if I even try to drive it, it acts like it's in limp mode. Any suggestions?

[adf]

Next I'd do a compression test and see if cyl #1 looks low relative to everything else and go from there.

[adf]

Forgot to ask, what did your spark plugs look like?

[HopskinsS4]

They seemed fine, they only have 10,000 miles on them

[HopskinsS4]

Also code goes away when idling but comes back flashing when driving. Car still has rough idle

[bmwpower603]

I'm just curious how many miles on your s4?
People say once timing work is done. You can run these into the ground. How come so many people are having compression issues?

[924Carrera]

Well there's the whole "scored cylinders, burning oil, engine is scrap" thing that seems to plague these cars and CAN, although it will not always, affect compression. I wasn't really aware of the scope of this problem when I bought mine, which had just had the timing components replaced, so I figured it was good to go. I have great compression across the board and burn a quart every 500 miles.

[HopskinsS4]

No idea what is wrong with this thing, it started out with a code for running lean and now it has cylinder one misfire. Idk if I damaged the injector when removing or what

[924Carrera]

Have you checked the wiring to the coil?

[HopskinsS4]

Not yet, I'm just trying to get feedback from people on here so I can go over everything that people suggest

[bmwpower603]

Well there's the whole "scored cylinders, burning oil, engine is scrap" thing that seems to plague these cars and CAN, although it will not always, affect compression. I wasn't really aware of the scope of this problem when I bought mine, which had just had the timing components replaced, so I figured it was good to go. I have great compression across the board and burn a quart every 500 miles.

Wow. Have you found the problem? Valve stem seals? That's a crazy amount of oil!

[924Carrera]

Wow. Have you found the problem? Valve stem seals? That's a crazy amount of oil!

Probably just cylinder scoring. These cars are notorious for it because of the unsleeved aluminum blocks and Audi's recommended break-in procedure, which involves driving really gingerly (which is really not the best way to break in any engine). Unfortunately the fix is an engine replacement. I inquired with JHM about their cylinder sleeving program, which puts an iron liner in at the cost of some pretty major machining, but at the time (a few months ago) they said they were not offering the program to new customers at this time because they had such a large backlog of orders already. Also, the procedure would require engine installation and breakin at their facility, which makes sense as they don't want the customer to screw it up and then blame their engine, but definitely adds a lot of hassle of trucking the car down to CA. I'm actually in Oregon so it wouldn't be as bad, but for a lot of people this is pretty prohibitive. Anyway, the car has so many other problems right now (mostly electrical, the engine harness is completely falling apart from really poor quality insulation) that oil burning is the least of my worries. My plan is to just keep it topped off and hope it doesn't get worse. If it does, I will have to take a huge loss on the car.

[bmwpower603]

Thank you for going into very, very good detail. I'm in the middle of getting ready for an engine pull on my 150k mile s4. (Due to my car being knocked out of time, or failed adjuster) But I'm hearing so many horrible things about these vehicles. I'm not sure if I want to go through with this timing refresh, and valve stem seal replacement. I love the car. Put some serious money into it with flywheel replacement. Would you say this car is worth keeping? Can I get away with a cheap JHM timing kit? Or should I go all out, with electronic adjusters and valve seals?

Maybe you can help me make an educated decision.

Mechanic said 2300 to do hg, valve stems, and all timing. (Labor only of course) and replacing all chains and tensioners

Thank you

[VinnysS4]

2300 is a steal for all that work if it is done properly. I was quoted 5grand just for timing refresh, and 2k of that was parts. SO if you can get away with 2300 in labor for timing, hg, AND valve stem seals, JUMP ON IT :) just my .02

[bmwpower603]

2300 is a steal for all that work if it is done properly. I was quoted 5grand just for timing refresh, and 2k of that was parts. SO if you can get away with 2300 in labor for timing, hg, AND valve stem seals, JUMP ON IT :) just my .02

Any idea on which jhm kit to purchase?

[924Carrera]

As far as keeping the car, I would say it's worth it if you aren't already having a bunch of other problems. They are nice vehicles for sure. But one thing I would highly recommend is having the cylinders bore-scoped before you go to the cost of pulling the engine. If you see bad scoring, I would honestly walk away (personally). There's no point in rebuilding an engine that's just going to suffer from oil burning. I presume you either didn't have any or haven't had the car long enough to know for sure. Not all the S4's suffer from it of course, but they all have the potential to, so checking beforehand would be very much worth your while.

[bmwpower603]

I actually had asked the mechanic to scope it. But he ended up just checking the compression instead. .

[924Carrera]

I actually had asked the mechanic to scope it. But he ended up just checking the compression instead. .

Yeah, compression check is a good and easy place to start. Bad compression will quickly point to some issues. However, there have been other people even on this forum who have had compression check out and have posted pictures of their scored up bores and stats of their heavy oil use. In these cases the car typically runs strong (like mine did before the electrical problems started, anyway) but still goes through oil. If your mechanic won't do it, I would press the issue because it's not that hard to do with the proper equipment and can save you an immeasurable amount of money and stress.

[HopskinsS4]

Okay compression is same in cylinder one as all the other cylinders. I replaced coilpack and spark plug and it's still throwing cylinder one misfire. Any other suggestions?

[adf]

Out of curiosity, can you post compression numbers?

Have you checked the wiring to cyl #1's coil pack?

[MG15]

Do you have piggie pipes or both cat converters still intact? Sometimes having the precat removed can help solve the issue. I have seen cars in the past misfire due to clogged cats. They became more clogged due to a bad coil/spark plug, but because the issue persisted for so long, even once the coil/spark plug was replaced, the cats were still very clogged, thusly causing misfires.

[HopskinsS4]

I do have stock precats still, the car started out running sluggish at higher rpm and now is getting worse. Clogged cat could be a major problem I guess

[Lucca M]

Okay compression is same in cylinder one as all the other cylinders. I replaced coilpack and spark plug and it's still throwing cylinder one misfire. Any other suggestions?

Check wires that go to the cyl 1 and try moving around injectors. See if anything changes.

[VinnysS4]

ok lets think this logically. A lean code means there is too much air in the system relative to the burnt gas. Lean usually = leak. Vacuum, exhaust, intake etc... if it is locallized to one bank (bank 2 in this case) then that means that on the bank of the engine that does NOT have Cylinder 1 in it, your Oxygen sensor is detecting too lean of a mixture. (too little fuel). So lets break it down because it could be any number of things. Usually the easiest and cheapest place to start is to check the intake manifold bolts and see if they have worked themselves loose. Before we go any farther then this... Do you have a VAG COM Cable or any other scanner that can read live data? We need to take a look at the Fuel Trims. They are usually the key to diagnosing a lean condition. It could be a dirty MAF sensor (tho most times that affects both banks) Also can you check to see if the intake flap is stuck or if it moves freely??
Onto to the Misfire code. If its Cylinder #1, then this is the opposite bank that the engine is running lean on. First, take the Coil pack and swap it with one on the other bank. Does the Misfire follow the coil pack? If it does, then you most likely have found the culprit ( you can watch the misfires happening with VCDS in the measuring blocks) If the misfire doesn't follow, try swapping plugs and again seeing if the misfire follows. If the misfire stays at Cyl Number 1, then swap injectors with another cylinder. What are the results? If nothing you can make number 1 stop misfiring, then you need to do a compression test and a bore scope. There are many things that could cause these codes, we need to atleast narrow down our search.

[924Carrera]

ok lets think this logically. A lean code means there is too much air in the system relative to the burnt gas. Lean usually = leak. Vacuum, exhaust, intake etc... if it is locallized to one bank (bank 2 in this case) then that means that on the bank of the engine that does NOT have Cylinder 1 in it, your Oxygen sensor is detecting too lean of a mixture. (too little fuel). So lets break it down because it could be any number of things. Usually the easiest and cheapest place to start is to check the intake manifold bolts and see if they have worked themselves loose. Before we go any farther then this... Do you have a VAG COM Cable or any other scanner that can read live data? We need to take a look at the Fuel Trims. They are usually the key to diagnosing a lean condition. It could be a dirty MAF sensor (tho most times that affects both banks) Also can you check to see if the intake flap is stuck or if it moves freely??
Onto to the Misfire code. If its Cylinder #1, then this is the opposite bank that the engine is running lean on. First, take the Coil pack and swap it with one on the other bank. Does the Misfire follow the coil pack? If it does, then you most likely have found the culprit ( you can watch the misfires happening with VCDS in the measuring blocks) If the misfire doesn't follow, try swapping plugs and again seeing if the misfire follows. If the misfire stays at Cyl Number 1, then swap injectors with another cylinder. What are the results? If nothing you can make number 1 stop misfiring, then you need to do a compression test and a bore scope. There are many things that could cause these codes, we need to atleast narrow down our search.

All good diagnostic advice but OP did say right at the start that he already swapped coilpacks and plugs and it made no difference.

[VinnysS4]

yup i missed that. just going through the normal process i use to diagnose something like this. best of luck to the OP. It should be easy to narrow down, just giving my .02
Most people tend to do half assed diagnosis of "throwing parts at it to see what fixes it" That is by far the DUMBEST kind of diagnosis. So when i suggest something like this, its to help eliminate that kind of mentality. Too many people follow dumb diagnosis procedures because someone else has had the same code, and they automatically diagnosing it as being the same issue. This ends up costing too many people too much money. They end up taking it to someone who actually does a proper diagnosis and they end up spending a lot less money. Everyone can offer suggestions, but in the end, a proper diagnosis (not throwing parts at it) will fix the car
Best of luck

[HopskinsS4]

Finally figured it out, it was a clogged cat. Thanks everyone for your input!

[Lucca M]

Finally figured it out, it was a clogged cat. Thanks everyone for your input!

glad you figured it out ! what did you do ? piggies ?