Tony Carlton

Hi all,

We have a UK '97 A4 SE with 84,000 miles, with a 2.6 12v V6 engine. We love the car, but we have a niggle with it.

The car starts OK from cold & runs fine until it is warmed up, when it starts "misfiring" at idle.

Audi replaced the HT leads & lambda sensors under warranty - but the "problem" was still there. Audi say they could not find a fault, as the computer was not recording a misfire code.

The effect is most noticeable when idling in traffic. You can actually feel the "misfire" thorough the seat - it feels as if the car is "kicking" slightly. It occurs randomly every couple of seconds or so.

You can also hear the effect by standing by the exhaust - it "pops" (ounding like a misfire / sticking valve etc.) every so often.

When driving the car it seems to disappear, except when travelling at say, 28-30mph in 4th gear when it feels as if the car is "kangerooing" slightly.

While the car was being "fixed", we had a 2.8 quattro as a courtesy car.
Very nice & it ran as smoothly as I would expect. Audi says the engine is different so the comparison is unfair.

I returned to Audi & complained to the chief technician. We both took the car out & he said "that's not right". They have now had the car for over a week & have tried replacing:

Injectors,
Coil Pack,
HT Leads, again !
Spark Plugs,

& the car STILL pops! They have also stripped down the inlet manifolds & examined the valves with an endoscope, but they're OK.

They then got Audi UK involved. Apparently the "misfire" at idle is caused by the EGR (exhaust gas recirculation) valve, switching on every so often at idle. While the valve is open, the injector shuts off - causing the "pop".

They then let us drive two Audi cabriolets, with the same V6 engine as our A4. These cars "popped" in exactly the same way as ours.

The "kangeroo-ing" is a separate fault. They are getting us a new throttle valve & ECU as they think it will solve the problem, but they are not
totally sure !

Although both the cabriolets "popped", I am not totally convinced. Can anyone confirm the operation of the EGR valve ?

Apparently, the 2.8 12v V6 and the 4.2 V8 use the same system (but not the 30v V6's). Has anyone else experienced this effect, or am I being hyper-sensitive ?

Cheers
Tony.

Y2K A4

Yea Tony I know what you mean. This happened to me before but different type of cars. I had a popping noise when acclerated with a Mercury Cougar I had, and I thought it was my Intake,injectors,or ecu. But later found that it was my EGR valve, so I replaced it and no more popping noise. I also had a different car that I had trouble with, My 3000GT. When I would punch it and when it reached 4000 rpm it made like popping noises and just suddenly lost power. I couldnt even beat a Geo Metro with it. My Mitsubishi dealer told me that I needed a new ECU because it was bad and that it will cost me around $1500.00 to fix it. But I didnt trust them so I had a mechanic take a look at it at a dealership I worked. We later found out that I had the wrong spark plugs in it. I had Bosch spark plugs when I needed the factory NGK ones. So I replaced them and ran perfect, so instead of spending $1500 to replace my ecu and not fixing the promblem I only spent $189 and got the job done.

Jake

Hi,

I'm an Audi Tech in CA. EGR...??? Doesn't sound right to me. By your discription it does sound like they covered all the right bases. I've never experianced that symptom here in the states.

You can easily confirm the possibility of an EGR problem, simply disconnect the vacume hose that goes to the valve. The vale is in the back of the intake manifold on the left (Drivers... no, passenger side in the UK) side of the intake manifold, next to the throtle valve. If it goes away... then, Yes it is indeed an EGR problem.

I'd be interested to here how this turns out, maybe I could use the info here in the states. I would appreciate an E-mail when it is resolved.

Best of luck!

Jake

Jake

Disconnecting the vacuum line would eliminate an EGR "triggering" fault. To truely be sure it wasn't a bad (leaking) valve, the valve would have to be removed and the port in the manifold plugged.

Jake

Tony Carlton

Thanks for the advice.

I wonder if the EGR valve is faulty - which is causing both problems.

I'll let Audi replace the ECU & throttle (they're paying anyway).

If the problems are still there, I'll try the valve itself & then back to Audi (again!)

I'll let you know how I get on. Should be sometime this week.

Cheers,
Tony.