WHAT IS GOING ON.

[Smackthatbird]

I already posted this on Facebook and got some good input, but I figured this might be a better place to ask.

This started all of a sudden last weekend out of nowhere. Driving around Richmond and I noticed that, at idle, my car was really shaking around. Absolutely no loss of power or problems once I was moving, it's just at idle. Sometimes it really feels like it's about to die on me, but it hasn't yet. I've had a solid CEL the whole time, not flashing, so it's not super-srs but I still want it fixed.

OBD scan gave me: Random misfires, misfires on all 4 cylinders, and system too lean codes.

I bought new coilpacks a few days ago, which was stupid, but the first time I scanned I somehow missed the random misfire code so I thought it could've been the coils. Of course, it wasn't.

Took it by Midatlantic Motorwerkes and talked to a mechanic because I would've just paid to have it fixed if he knew for sure what it was, but all he said was to maybe try getting my fuel pressure checked at the Audi dealer in Charlottesville... and that's an hour drive and would definitely cost me and I'm really not convinced it's a fuel pump problem, because everything I know about that suggests that I'd be having power loss issues, which I don't.

Any thoughts?

If you think it's the fuel pump, is that really possible without at least some noticeable power loss? I CAN drive down to Cville to have it tested if it's really a good idea.

[JPolen01]

Car? Mods?

Sent from my DROIDX using Tapatalk

[ScottyB]

you have an A4 right? 1.8T or 2.0T?

[PDenbigh]

Vacuum leak.

[ViPER1313]

MAF sensor. Go unplug it and see if it smoothes out. Exact same symptoms and codes my buddies Jetta had. I don't know why VW Audi read bad MAFs as cylinder misfires, but they do.

[Smackthatbird]

Thanks for all the fast replies guys.

It's a 1.8T 03 A4, stock because I've been too occupied trying to get everything working right to mod anything, lolz.

MAF is something I've been thinking about. I guess it's so easy to check that I might as well do that.

As for vacuum leaks, I'm inclined to think its not that because of the random misfires and the fact that its across all 4 cylinders.

[Smackthatbird]

Oh, and I'm not sure if this really matters, but its at around 95.5k miles. I've had suggestions about the timing belt, etc. but that was all replaced around 79k.

[D_Eclipse9916]

Misfires can be so many things, but check

MAF- Unplug and plug back in, see if it changes the idle.
Spark plugs, all of 8 bucks total at advance auto, might as well (coppers)
Vacuum leak (yes it will show up across all 4 cylinders as a misfire)
Coil packs ( you have them, might as well swap, but I doubt all 4 cylinder misfire)


I highly doubt its the fuel pump, but may be a regulator. If it was the fuel pump you would have issues other than idle.

[Smackthatbird]

Misfires can be so many things, but check

MAF- Unplug and plug back in, see if it changes the idle.
Spark plugs, all of 8 bucks total at advance auto, might as well (coppers)
Vacuum leak (yes it will show up across all 4 cylinders as a misfire)
Coil packs ( you have them, might as well swap, but I doubt all 4 cylinder misfire)


I highly doubt its the fuel pump, but may be a regulator. If it was the fuel pump you would have issues other than idle.

I'll definitely give the MAF unplug a try.
As for the spark plugs, a guy at Advance tried to sell me them, but they're $14 each for my car, and I'm really not trying to spend $60 on something I don't need, haha. I just replaced them at 80,000 and I'm pretty sure ours are supposed to last a loooong time. Also, I think it'd be one or two cylinders misfiring, not random ones across all 4.
And I should've clarified - I did put all four coil packs in and they had no effect.
I'm going to have a look at the vacuum leak issue, but I think if that's what it is, it's a broken valve, not a hose, because I've seen some reports of that specifically causing this. Just haven't had time, parts, or tools to do anything in regards to that yet.

[SlimKlim]

There have got to be plenty of plugs out there that cost a lot less than $14 each, but if you replaced them somewhat recently then they should be fine, unless the car has been running extremely rich or lean for a long time. Since the coils are new and the plugs aren't that old, sounds like it's probably the MAF or a leak like DJ and Adam suggested.

It could also be a seriously effed up idle control valve or similar. I'm not sure what they are called in the VW/Audi world but my car has a little ICV under the intake manifold that likes to sieze up and cause all sorts of weird issues when it gets old. A good dousing of brake clean has it working like new again though.

[PDenbigh]

I'm not a VW guy, but I still say vacuum leak. It will show on all 4 and it will create a lean code because it's pulling "unmetered" air. Thus, it's not putting out enough fuel for the actual amount of air, which would result in a lean condition.

A bad MAF could also create this situation. Personally I've never had a MAF go bad though, so that's why I put it as #2 on the list.

Probably not plugs or any other wear items because it happened "all of a sudden."

Unplug the MAF, that's easy. If that changes nothing, spray various spots around the engine with starter fluid (avoid sparks or excessive heat of course). If the idle takes off, you have a vacuum leak near where you just sprayed it.

[ViPER1313]

I would normally say vacuum leak as well but those VW/Audi MAFs suck a huge one.

[davej]

If you need an extra DV to test with, I've got some good ones from the s4. If it turns out to be a vacuum leak, the seal/spring in them can be pretty suspect.

[NTIman]

I'm not a VW guy, but I still say vacuum leak. It will show on all 4 and it will create a lean code because it's pulling "unmetered" air. Thus, it's not putting out enough fuel for the actual amount of air, which would result in a lean condition.

A bad MAF could also create this situation. Personally I've never had a MAF go bad though, so that's why I put it as #2 on the list.

Probably not plugs or any other wear items because it happened "all of a sudden."

Unplug the MAF, that's easy. If that changes nothing, spray various spots around the engine with starter fluid (avoid sparks or excessive heat of course). If the idle takes off, you have a vacuum leak near where you just sprayed it.

I said vacuum leak too. Usually on yotas if the MAF is bad it isn't bad enough to create misfires, but definitely throws a lean code. You can also pull the MAF and look at the wires to make sure there isn't a leaf or something on them. Yes, it happens. A lot.

[DierwulfBL]

just as another option to look at, I have seen cylinder misfire codes being thrown for a bad injector before, it was ignored and because of the lean condition ended up burning a valve. This person threw just about everything at the car to fix the issue except injectors, so just keep that in the back of your mind.