So my brother got himself a 2001 S4 with about 100K miles on it. The car was purchased from a person I knew through my Subaru forum (I myself own a STi ).

Prior to purchasing the car, we knew that the he had put in a GIAC chip in the car and installed an exhaust system (not sure which manufacturer). He said that the car throws a CEL time to time indicating a random misfire. He gave my brother his code reader and told him to just erase the CEL which he has been doing. He said he replaced and coil packs on it and have a new fuel filter for it.

I am not familiar with GIAC chip and not sure if that chip is causing the CEL to come on or he might have something else going on. I know the car is in good shape. I just want to determine what is causing the random misfire code and how to eliminate.

Also, any other suggestions and recommendations on the car is very much appreciated. Thank you very much in advance.

p.s. My wife now wants an Audi...... Currently, I have a 07 STi and she has 08 WRX....

 

my guess is the coil packs, the chip isnt whats causing the misfire but the extra stress it puts on the engine can result in the misfire. see if you can find out what cylinder specifically is misfiring using a computer

 

the coil packs could be the problem, but it's most likely the spark plug gap. your gonna want to replace the ones that are in their now, and put copper plugs in its place, and gap them less than what the oem suggests. if it's giac, i would contact them and ask what the optimum tollerence is for the gap, and what plug they suggest. when running an ecu mod, it's pushing greater boost and could cause the plug spark to blow out, thus, creating a miss fire code..... maybe... i'm no expert thats for sure.... but, you become very well informed of how your car works and doesn't work the longer you own an s4 good luck!

 

Thanks for the reply. Maybe I should have explained in little more detail. He started to see the misfire code after the GIAC chip was installed. Then, the mechanic told the previous owner that the coil packs could be replaced to fix the problem and he did, but the problem remains there.

I know how to hook up my tactrix cable to my STi, but not sure what software or program to use to find out what cylinder is indicating the misfire.

My brother is very excited about his S4 and I am too. I know it is 9 years old, but I love the car myself and I want to see that car run for a long time. Since we are both new to Audi world, I am sure we will be asking more questions. But at first one at a time.

 

Thanks for the reply! as I mentioned above, not sure if the coil packs is the problem or not. But I am going to have my brother take his car to the mechanic I take my car to. Until then, as for our learning experience, we wanted to see if we can find out what could be causing the issue.

As for the suggestion on the plugs, we can replace them and gap them at the spec GIAC recommends. Any advice is appreciated.

 

My brother plugged in the code reader and this is what it said. I have never used a code reader so I am not sure what the entire message means, but I can tell it is indicating a P0300 Random misfire. What does the rest of the message mean???

1 Code
P0300
MIL ON
Monitrs
0 Inc
7 Ready
Misfire
Fuel
Comp
Catlyst
Evap
02 Snsr
02 Htr


Thanks for your help!

 

I own a 2004 audi A6 2.7t and it has the same engine as the 2001 audi S4. I too have a GIAC chip in my car, and my car has had two misfires which caused two ignition coils to fail. The first time my car misfired my car started to shake, and the check engine light started flashing. Needless to say I had not a clue what was happening. I parked my car at my cousins house, and had it towed to the nearest audi dealer. The dealership charged me a lot of money to change one ignition coil. The second time my car misfired I began to worry that I had to pay a lot of money to replace something that was replaced a few weeks prior. I did some research and learned that it is easy to change an ignition coil for cheap. The problem is that the ignition coils seem hard to reach in the audi A6 engine. I have not attempted to change the coil yet, but I could use some advice on how to change the ignition coil. Any suggestions?

 

I would say spark plug gap or if it's popping up on the same cylinder then check the ignition control modules.