I need some expert help here please...

About 2 months ago, I'd noticed the loss of power with my 2001 A4 Avant V6 2.8L.

The car starts and runs smooth, but it was evident that the snap under acceleration was no longer there one day. I used the Memoscan U280 scanner and came up with these codes:

16814- main catalyst efficiency below threshold (16816 closest)
16684-random misfire detected-any cylinder
16685-cylinder #1 misfire detected
16687-cylinder#3 misfire detected
17831-secondary air injection system (B1)-Flow too low

I cleared the codes and it seemed to fix the issue (probably coincidence) but the issue came back within a couple of weeks.
I scanned again and now came up with:

16804- main catalyst efficiency below threshold Bank 1 (16806 closest code)
16814- main catalyst efficiency below threshold Bank 2 (16816 closest code)
16684-random misfire detected-any cylinder
16687-cylinder#3 misfire detected
16688-cylinder#4 misfire detected
16712-knock sensor #1-circuit-low input (bank 1 or single) (16711 closest code)
17734-Cylinder #2 knock control limit attained

Going up hills or acceleration at this point is weak. Under heavy load you can hear the car knock/ping so I pull off the accelerator.

I suspect the cats, knock and such are results of the cylinders misfiring. Fix these issues and the others go away ( I think!) Cats are a couple of years old with new O2 sensors replaced at the same time.

So started with cylinders 1 & 3 to have misfire, but now 4 and cylinder 2 misfire is gone, but the "knock control limit attained" exists now...I do not know what that means.

Can someone please point me in a direction to remedy this issue? I need fast help as this is my only source of transpo and don't want to "F" this thing up.

Thank you!!!

 

Try this:
Need help w/ stored engine codes. Pre-Purchase inspection completed. - AudiWorld Forums

 

I cleared the codes a couple of times with the key in the on position and then with the key in the off position.

That seemed to fix it. Ran like a champ this last week. Now it's back to cylinder misfires and loss of power. Keep getting the same random cylinder misfires with no other codes. tried to clear again, but it is not correcting the problem this time...engine still lugs.

???? Damn!

 

Have you checked the knock sensor itself? It could also be the cam chain tensioner sensor on the front of the cylinders, however for both to go bad, not likely.

Have you checked or replaced your spark plug wires lately?

Also, not to be an A$$, but I'm assuming your oil level is good? Oil light doesn't flicker now and then?

Here's what the manual(s) say, not that it helps tremendously, but here you go:

1. Loosen knock SENSORS and re-torque to 20 Nm (15ft lb)

2. Correct cause of abnormal engine running noises (yes I know, VERY VAGUE)

3. Fill with 91 OCTANE minimum (and my .02 add some fuel cleaner)

BENTLY MANUAL says:

Poor quality fuel

Knock regulation module in ECM Faulty (ECM is bad)

Open/short circuit in SHIELDING of knock sensor wiring

Loose contact in harness connector for knock sensor

KS 1 -GS61 loose

Abnormal engine noises (aux assemblies loose, engine damage)

Scan your ECM with your VAG and read measuring block in Display group 13 to see if the ignition timing retarding is correct......

If the timing is off, or the 'retarding' it will cause these faults as well....or the sensor itself for the timing is bad or faulty....

 

Sorry brother, here's where I would start. BTW, the KS1 is the knock sensor....here's a little how to by, believe it or not AutoZone, to test knock sensor:

| Repair Guides | Components & Systems | Knock Sensor (ks) 1 1 | AutoZone.com

 

FWIW, I checked the coil last night and swapped wires on the same coil pack and it had no change.

Checked plug wires by swapping sides, no change

It's definitely the 1-3 cylinder bank.

Was suspect of cam tensioner but why would it run great for a week and then come back?

I'll try the suggestions. I really do appreciate the help!

 

btw, oil level is fine use 92 octane and ran fuel cleaner a few times. Cam tensioner does not make any noises.

 

I've had the cam chain tensioner SENSOR go bad...it's a cheap part and relatively simple to fix. You can also test it. It's either that or your cam chain tensioner itself....HOWEVER, if you cleared the codes and it ran FINE, then started again, it's your SENSOR.