Alright guys I need help. I've officially tried everything I know (which isn't much) and nothing is fixed. Here's the issue:

A while back while driving on the freeway (65 mph or so), I got a CEL. Checked it when I got home and it was a couple of random misfires. Cleared the codes, hoped it was a fluke, but it was not as it happened again.

Codes: P0300, P0302, P0304, P0305, P0306
(Random misfire + cylinders 2, 4, 5, 6)

So far I have:
Changed the spark plugs (twice, as the first time I changed I put in NGK but somewhere I read german cars need Bosch, Japanese need NGK... So I put Bosch in the second time).
Changed spark plug wires.
Changed the coil pack.
Changed the valve cover gasket (I didn't see much oil on the plugs when I pulled them either time, but I figured why not).

I would have suspected the second coil pack I bought (from ECS) was bad, but they're both throwing the same codes, i.e. never do cylinders 1 or 3 throw a bad code but the rest do, as well as the "random". (also note it's a 2.8 so it's one big coil pack instead of one for each cyl.)

I can drive around town just fine but the code only comes up when I've been on the freeway for about 10 minutes.

The other thing to note is that I never notice an issue with performance. The only thing I can see wrong is the CEL coming up. There's no shake or shudder, it idles fine, I don't notice any loss in power, etc. In fact if I put a piece of electrical tape over the CEL, I'd be just fine (obviously I'm not going to do this, but just to give you an idea).

Thanks for any suggestions!

1999 Audi A4 2.8 Quattro, 163k

 

Upstream O2 sensor.

 

Wouldn't it throw an O2 code? I have never seen one on this car. I hear they are a common issue though.

 

I should also mention, rarely I've been getting a secondary air injection CEL while on the highway

https://www.audiforums.com/forum/b5-...ighway-212502/

Dunno if that would have any relation. I just haven't got around to fixing that one while I deal with this misfire.

 

I've been through this entire cat and mouse game myself already. You are not going to get an O2 code because it's "crippled" not broken.

Stop wasting your time and money. An upstream O2 sensor is easy to DIY and even of I'm wrong: you probably needed one anyway.

Just replace the upstream O2 sensor w/a quality replacement. Clear the codes and see if it throws any codes after the swap.

G/L

 

fair enough.

2 things then:
What size socket are the o2 sensors? I don't have a crows foot socket.
There is a sensor for each bank right? I'm getting cel's for each bank so I'll have to do both (if there are two).

 

7/8" or 22mm for the socket size. If you use a socket, you're going to have to cut the wires on the old one, but that leaves you stuck on the new one.

I've noticed that if you have a short enough line wrench, you can get to the upstream fairly easily (considering).

You don't necessarily have to replace both. I had codes for every cylinder and the upstream fixed everything.

The upstream O2 is the easiest and quickest to change. Always start with the easiest and cheapest thing first. Then work your way up from there. Why waste money on something you may not need?

Also: Check for vacuum leaks and cracked or missing hoses while you're in there. I bet you'll find at least one (check up by the firewall).

Again:G/L

 

welp, I replaced the TWO o2 sensors and now i'm getting o2 CEL's... super.

p1196 (Bank 1 Sensor 1 Electrical Malfunction)
p1197 (Bank 2 Sensor 1 Electrical Malfunction)
p0154 (Sensor Circuit No Activity Detected)

verbatim of this pour sap: Need help with error codes P1196, P1197, and P0134 - AudiWorld Forums

sadly the guy in that thread says the sensors he bought are crap. these are the two I bought: Amazon.com: Bosch 13842 Oxygen Sensor, OE Type Fitment: Automotive
They are the same on ECS and on Rock Auto, so I'm thinking the sensors are okay.

 

The first O2 sensor I replaced was defective also. It had me so confused.

Bosch makes good parts, but for some reason our cars have the worst replacement performance issues I've ever seen. It might be because of the low bandwidth "Warm up". I don't know.

Cross reference your new codes with the Ross Tech WiKi and see if it's not something else also.

 

No dice.

Changed both o2 sensors as well as a small piece of vacuum tube. Still getting the codes.