William Barnhart

As title states, I have a 2003 A4 3.0L Quattro sedan. Here's the issue I'm having...

The car will start and run. It seems to rev smoothly but when it idles, there's an obvious misfire. It will idle for about 10 minutes and then it will quit. When I start it back up, it takes about 5-7 seconds of cranking before it will start. When it starts up at this point, the EPC light is on and is obviously running in "safe mode". Previous issues with the car were a bad ABS wheel speed sensor (no speedometer as well as no ESP), recently had the water pump & timing belt replaced. It ran great for a couple of months as I was driving the car about 70 miles a day to work and back. It began having issues where it wouldn't want to start. It would act as if it was flooded and when it would finally start, the smell of fuel was overwhelming. It gradually got worse so I finally took it to a local shop that specializes in German vehicles, and after a couple hundred bucks to fix a (bad circuit to the ECU, it seemed to fixed. Then a couple months later, it started having the same issue. It would die on me in traffic, and when it would finally start back up, it was in EPC mode. I've run several scans, and the most recent scan popped up multiple cylinder misfire codes as well as an O2 sensor code. The only thing I have done thus far is replace the CPK sensor as well as the ABS wheel speed sensor on the driver side. Neither fixed either issue. Perhaps I'll try swapping the ABS sensor on the passenger side next unless someone knows which one usually goes bad. I'm not a noob when it comes to working on cars, but this audi has been one big pain in the ***. I hate to take it back to have it serviced because as we all know, people want an arm and a leg to work on these things.

Has anyone had a similar issue? Or maybe steer me in the right direction? I was going to replace the cam sensors next but I'm growing impatient and I hate wasting time and money. Both are limited at the moment. Lol.

PLEASE HELP! =) THANK YOU!!

turbo510

I doubt that the ABS speed sensors would have anything to do with your problem, especially since you have poor running and stalling at idle, when I suppose the wheels aren't turning. Likewise, I don't think the cam sensors are the issue. How about the engine speed sensor, which is on the driver's side of the bell housing? Those things can cause problems like those that you describe.

A few other things to consider: loss of power while driving, accompanied by the EPC light, can be a brake light switch that needs to be replaced. Inexpensive and not hard to do. If you have occasional surging during warm-up, which my 3.0 did when new to me; crankcase pressure control valve. But the most difficult one for me to solve was hard starting, high idle, EPC on, and limited power. The fault code would be for the ESS (engine speed sensor), but after changing that, the engine seemed to run better for a while, then the symptoms came back. The clue happened one day as I changed lanes, and happened to run a tire over a reflector dot in the road. The slight shock set off the lower-power symptom again, so it was triggered by the shake from the road bump. So it was a connection somewhere, and after pulling the ECU and fuel pump relays for a look and contact cleaning, I found that one of the two sets of contacts on the ECU relay was making a very marginal connection when the coil was energized. Re-flexing the brass arm completely solved that problem.

William Barnhart

I already changed the Crankshaft Position Sensor (CKP) on the driver's side of the bell housing...is this the "engine speed sensor" you were referring to? Also, it doesn't really run poorly but the idle isn't as smooth as it should. It'll just quit randomly, idling or driving. When you restart it, it goes into limp mode with the EPC light on. Then it will run, but won't rev over 4k. The ABS sensor was replaced to fix the "no speedometer" & "ABS / !" warning lights, as well as the ESP. I doubt the ABS sensor is related to the other issue of it quitting. I am going to go ahead and replace the passenger side ABS sensor as well since they are fairly cheap.

Also, where are the brake light switches you were referring to? I'm also going to check the relays as well and see if anything looks sketchy there. I appreciate the input and hopefully it will help me track down the problem! =)

turbo510

The brake light switch is actuated directly by movement of the brake pedal, so it is right above the pedal, mounted in the bracket. At autohausaz.com the Facet brand is $11, comes with a sheet of actually decent full-color instructions. You just remove the knee bolster, disconnect the wiring to the switch, then give a bayonet-type twist to remove the switch. The new switch automatically sets itself for proper actuation, but you have to follow the instructions.

Any chance that the fuel pump is just getting marginal? That's another thing that I had to replace last year. My '05 has almost 215K miles on it, and has been reliable since the episodes with the relay and fuel pump. Also, my habit is to disconnect all accessible connectors about once per year, spray the contacts with electrical contact cleaner, even those in the ECU box. I go over the engine grounds too, just loosening, spraying WD-40, then re-tightening. I've had really no electrical problems to speak of, so I continue to do this.

Barrelmaker

Having the exact issue with my '03 A4 Avant 2 days in a row except that with numerous cranking the immobilizer icon showed as well. Can't be the fuel pump or the Crank Position Sensor as the ECU has to signal injectors to fire and gets that signal from the CPS. Obviously they are and flooding the engine as well.
From other posts changing the fob battery will not correct an immobilizer issue. There's a pick up coil (in column or dash) that receives signal.
Sat in a parking lot yesterday for 5 hours trying different things and when I pulled the fuel pump fuse it started and reved high (2 to 4 K) then died again. Leaving the fuse in produced no fire period. Weird that it would start that way.
Anyway, sitting befuddled for another 15 minutes I tried it one last time and started like nothing had happened and drove me home, it ran perfect...

WTF is going on with the system in this vehicle...

turbo510

If the engine started by pulling the FP fuse after lots of cranking, I would assume that's because as it leaned out due to ingesting air only, briefly there was a burnable mixture. Have you checked the coolant temp sensor? One that is sensing abnormally cold will easily cause the engine to flood.

SmellyCat

my 3.0 had a odd start that would take forever to restart. I think it was flooding When it occurs , Floor the gas pedal when you crank, that cuts the injectors off. See if that starts it. I had a temp sensor under the throttle intake that was telling the cpu the wrong temp and causing it to flood at start up. I’m not sure why I’m typing with a line in the letters. Sc

Barrelmaker

I haven't checked the coolant temp sensor (and will research) and agree the problem does include a smell of fuel but what's contradictory is that when I switch the key to run position the rad fan spools before crank... Would that not indicate a false hot condition - or perhaps the sensor is so damaged it's readings would be erratic at best. Any thoughts would be appreciated, thanks.

SmellyCat

My radiator fan turns on when I turn the key. Think it’s due to the car automatically engaging the AC.

turbo510

A couple of tips about that sensor, which is inexpensive. (1) Remove the corrugated plastic duct between the MAF sensor and throttle body plastic duct. You first unclip two spring retainers at the MAF housing, then use a large channel-lock plier to squeeze the big band clamp and move it away from the duct. Be careful as you relax the pliers, the springy clamp will be under a lot of tension. (2) The Coolant temp sensor will now be accessible. Disconnect the electrical connector. Next, tie a long piece of a string such as dental floss to the retainer clip, before prying it out. These things have a tendency to get loose and lost otherwise. (3) With engine off and cool, pull the old CTS out using your fingers, or if stuck, twist and pull with pliers. Usually a small quantity of coolant is lost, but keep the reservoir cap on. Clean the socket where the sensor was removed, and be sure to retrieve the old O-ring. (4) Install the new O-ring on the new sensor, wipe a little bit of Vaseline on the O-ring, then push it into place. Once the retainer clip is reinserted, connect the wiring and reinstall the intake duct.

If this does not correct the radiator fan running when the key is turned on, a couple of reasons could be: (1) Radiator temp switch is defective or (2) there's a problem with the fan control module.