2002 Audi A4 1.8T Quattro

Just recently, I ran into a problem with the Audi and would like to have some advice.

Symptoms:
The car accelerate slowly and gradually if the gas pedal is pressed lazily and will maintain any speed, however, if the gas pedal is pressed in a hurry, the engine vibrates, and the car hesitate. The engine and EPC light is also on.

Therefore, I got the car on the scanner and received those two diagnostic errors:

P0304 Cylinder 4 Misfire Detected
P0688 ECM/PCM Power Relay Sense Circuit

So far, I have cleaned the throttle body, checked the MAF and tested each spark-plug to ensure that they all fire up when the engine is cranked – (Coil pack seems ok). I still have the same Symptoms.

What should be verified next?

(I’m trying to avoid brining the car to the dealership, as everyone else, the money is a bit tight, and would rather fix it at home).

 

Shopkey lists P0688 as 'Power Supply Relay J271, Load Circuit Open' and suggests to check the ECM power supply relay, J271 for fault and/or activation, then runs through a wire/voltage check which if good means to replace the relay.

#3 in the E-box

Apparently a fairly common fault.

 

Thanks Jim, i'll give that a shot,

 

I opened the e-box plenum chamber, there is nothing suggesting J271, however, as per the ebox diagram, the voltage supply relay is at position 3, and this relay switch has number 219 on it...

The relay switch is $75.00 – Before I go purchase one, how do you test if it is indeed the root of the problem??? It doesn’t look burnt or damaged?!..!

 

I cant see the prongs, but if its the same as any Bosch 30amp relay like 99% of the others out there, you can get them cheap... or free at the junkyard

http://www.google.com/products?hl=en...ell=1&oi=spell



How ever.. 12v applied between 'T' and '86' should click the relay. When clicked, you should be able to read 0 ohms between '30', '87', and '87A'. There is also a diode in there to prevent voltage spikes when engaging/disengaging. If it goes, it can spike your ECU...

 

Hey Jim,

I've performed the test you suggested, the relay switch click and they all come back to 0 - which shows that the switch is working fine...

I'm lost, any other ideas?

 

Not really at this time.. I'm going by research since I've never had this problem


Lemme look around some more...

 

In the OBD codes, it also says that it could be a faulty exhaust valve. So after a bit of reading, some suggested to use the Seafoam to clear the engine ...

What are your thoughts?

 

Worth a shot for the misfire, though I dont think that would set the P0688 code.

 

Problem fixed!

For those interested, I have fixed the misfiring problem by:

1- Changed the fuel filter
2- Change the sparks
3- Change the 4 ignition coils
4- Cleaned the fuel injectors
5- Cleaned the throttle body and MAF
6- Seafoamed everything

I also brought the car to a local parts store and had them remove the engine error.

Now the car runs perfectly!!!

Thanks for the recommendations.

Cheers,