Greetings,

I was driving home in my 2000 A6 4.2 up a steep hill, when as the vehicle attempted to downshift when under load, the flashing CEL misfire engine light started to blink, and then stayed lit. The car shuddered and shook at the same moment, and felt almost like a loose wheel. As soon as I took my foot off the accelerator, the shaking stopped. I got home and used my ODBII scanner which reflected the following codes: P0301, P0303, and P0308 - all major misfire codes on cylinders 1, 3, and 8, which on this car are the first two on the passenger side, and the last on the driver's side. So the journey began...

After spending time researching on this site, I started by going from least complicated (less expensive) to more complicated potential fixes, starting with the fuel system. My car has 135,000 miles and had not had the fuel filter changed since 100k, so I changed that, but it did not solve the issue(s).

Next I changed the spark plugs, again no improvement.

Next I tried moving the coil packs to try and move the misfire, which did move on two of the misfiring cylinders, 1 and 3. I replaced all 8 coil packs and now only had a misfire on number 8.

Next I guessed that the fuel injector was bad or clogged on number 8, once I saw the price of a new one ($150 was the cheapest I could find) and figuring that if one was bad, the others were probably close, that it would be better/cheaper to have them cleaned and balanced. I pulled the fuel rail, pulled the injectors, and sent them to fuel injection connection. For around $125 they cleaned and balanced all eight. I re-installed them, and ughhh, P0308 again.


Engine with fuel rail removed.

Next I tried running without the MAF connected to see if I had a bad ECM module giving bad timing info, but the fault code occurred with the MAF on and off.

I then turned to the bellows type secondary variable intake crossover valves at the front of the manifold. I had noticed in the past that one of the plastic arms was broken and had replaced it with a gruvenparts aluminum one.


Notice that one is actuated, the other is not.

However, I realized that the reason the other one broke, was that the valve was stuck. I tried to manipulate it by hand to no avail. I tried cleaning/lubricating the crossover flaps with throttle body cleaner through the TB, but it was still stuck.

I removed the manifold cover, and secondary variable intake actuators and found the flap to be completely seized.


This is the inside of the manifold cover, removed.

The flaps are plastic, so you don't want to put a lot of pressure on them. I pulled the seized one forward about an inch to release the pivot out the front of the manifold, then cleaned, lubricated and reinstalled.


Notice the cylindrical pivot slides out about an inch, but no more. Enough to clean and lubricate.

It now activates and returns with ease. Bolted everything back together and the variable intake now works as intended.


Variable intake crossover flaps.

The P0308 code disappeared, as a bonus I have increased power and mileage, and the engine is much more responsive thanks to the other items replaced during my attempted fixes.

Thanks to everyone who has posted on this forum in the past, I spent many hours reading posts and getting ideas. It saved me from the dealership "replace the manifold" solution that was expensive and ultimately unnecessary. I hope this helps someone else out, I had not seen pictures of the inside of the manifold on the forum in the past.

Cheers,

Ebenezer.

 

Good write. For my experience, ART engine are seldom got coil and injector fail. but stuck intake flaps, and broken cam tensioner arms are quite often. Also this engine is very sensitive about timing, half notch can make enigne runs like crap. good luck

 

thanks for all the description of what you did... something similar happened to mine.

 

My flaps a are both seized as well. What did you use to free and lubricate them? I have no movement and they feel like they will break if when I try to turn them. I am stuck and cant free them up.

I am super excited to fix and get back together since I just bought this car super cheap and I am sure this is the problem and can't wait to see how the car runs with full power.

Thanks

 

Don't force them. There are two bolts on each of the bases where the actuators attach. Remove both bolts on each pivot base and gently work them straight out. Keep in mind that they may be resting on each other- hung up in between their range of motion. If they are really seized you may need to take off the manifold cover to get access. The flaps are plastic, so be Gentle!

 

hey i have simular issue did your car make alot of noise which came frrom directly under manifold? i have misfire codes also but car makes terrible noise from under intake

 

Mine didn't make a lot of noise, but it shook badly during the misfire. It felt like a flat tire until I let off the throttle.

 

So after breaking the flaps that came on the car I got super lucky and found a new complete manifold 15 mins away that I was able to negotiate down from $300 to $100 with tax. After carefully working the flaps back and forth like i was told earlier in the post I freed them. I used sand paper to clean out the grime in the holes where the flaps pivot and used the best parts from both to put it back together.

My never made any loud noises before and actually ran pretty good both before and after. (Good News) There was a power gain and the misfire codes for 1,4, and 5 are now gone along with the intake manifold pressure codes. (Bad News) However I still get a flashing CEL and code P0300, P0307 and P0308 every time I use over 75% throttle for more than 4-5 seconds. From 9 codes down to 3 now.

I have read another thread that suggest that this may be fuel pressure but I really want to see if you have any ideas.

I have swapped coil packs, spark plugs and air filter and no change. Seems to be running good. I do hear a faint shutter when I take off from a low speed if I'm next to a fence or car for the sound to reverb off of. I believe it is the flaps working and hope it is not the cat. I know unburned fuel makes the CEL flash and over time can ruin the cat but the plugs are completely white and have no sign of carbon build up from unburned fuel.

Thoughts Ebenezer or others?

By the way, I bought this car to flip but have fallen in love with it and will be keeping it. May even sell the Vette now. I have 3 A4s as well as a GLI. Flipping Audis is fun!

Thanks,

 

I flipped mine twice, it wasn't fun and the insurance company totalled it.

 

Check to see if both flaps are activated when you start the car when cold, that will tell you if the misfire is related to the range of the flap intake travel affecting the timing or something else. Glad to hear you are making progress on the codes