Hi guys, 2001 Audi A4 Quattro Wagon. I've gotten this twice while on the highway lately:

17536 - Long Term Fuel Trim mult.,Bank1 System too Lean

Then twice this week when I go to start the car, it runs like **** at 1200 rpm, and I get these:

16684 - Random/Multiple Cylinder Misfire Detected
16685 - Cyl.1 Misfire Detected
16688 - Cyl.4 Misfire Detected
16686 - Cyl.2 Misfire Detected

However after a few minutes it warms up and idles fine, and drives fine.

Does this logic make sense? Once the o2 sensors are warmed up enough to work, the ECU puts the mixture in closed-loop mode, but before that it's running open loop and calculating the expected mixture based on the mass air flow sensor. My guess is the MAF is on the fritz.

If it weren't for that, I'd say the coil pack is going, but it idles and drives beautifully once it's warm.

Thanks!

 

Random multiple cylinder misfire is usually the result of a lean fuel mixture. If your car has both a MAP and MAF sensor, you may want to take a look at the MAP rather than the MAF. In most FI sytems the computer looks at the MAP and the ECT before the engine starts in order to compute the initial AF ratio.

 

Ah interesting, thanks for the reply.

I replaced the MAP this weekend. The car hasn't had the initial idle problem since I replaced the sensor, though I didn't drive a ton. The idle is still not as smooth as it used to be, and I got this one again, but this time at idle instead of highway:

17536 - Long Term Fuel Trim mult.,Bank1 System too Lean

For what it's worth, I've gotten this one since I've had the car, and it still comes up (though I assume it's unrelated):

16825 - Evaporative emission control system

Any idea what I should look at next?

Thanks!

 

You may want to replace your coolant temperature sensor (cheap and easy). If the ECU overestimates the engine temperature during a cold start, it will fuel-starve it (too lean).

 

Thanks! Will do that this weekend. Where on the block is the coolant temp sensor?