I posted this item to a related thread, but it appears a new post was more appropriate. Here’s the issue: a recent trip over the Sierras after heavy snow involved some uncharacteristic slipping and sliding in my 2003 A4 quattro with 1.8T and Tip, which leads me to believe I may have a problem w/ the ESP (Electronic-Stabilization Program, described below)... at least that’s my guess, I’m looking for advice.

I’ve made dozens of trips on I-80 this winter in every road condition imaginable without the least concern for traction loss or skid. For better or worse, I drive in Tip mode, stay off the brakes, “downshift” to maintain desired speed. I’ve never once slipped or skid.

I passed chain control expecting a routine drive of some 40 – 50 miles thru heavy snow accumulation from previous 24 hours. I started uphill at 30 – 35MPH behind an SUV when the tail of my car abruptly kicked out to the left, pitching the vehicle nearly sideways to the direction of travel. I let off the gas, turned into the direction of skid (uphill), ESP illuminated, the car corrected. ESP light turned off. I thought this was a one-off and continued as usual. No other traffic at the time (4x4, AWD, 2WD w/ chains) was having problems with the conditions; most traveling 40 – 45MPH, many faster.

Long story short, at speeds over approx 25MPH the ESP repeatedly illuminated and the rear of the car would start to kick out to the left, driver’s side. I had the distinct impression as I was driving that the nose of the car appeared to be pulled slightly to the right, as if the wheel alignment was off. When hitting heavy bumps, even at 20MPH, the ESP illuminated and the car felt as though the tail was going to kick out to the left. I considered turning off the ESP, thinking it was somehow causing the problems.

Spent the better part of 50 miles behind a truck doing 20MPH or less. Once back on clear pavement, no more problems. Had tires checked, reasonable tread (about 10K to go) and properly inflated; I’ve rotated ‘em about every 5k for the past 30K; very even wear.

For those not familiar, the owner's manual describes ESP as follows: ESP helps control the vehicle in critical maneuvers like curves. The system operates across the entire speed range in combination with the ABS system. The wheels are prevented from spinning by adjusting the engine power to conform to all road conditions. The system can be activated or deactivated bypressing theESP button.

Thoughts or comments would be appreciated.

 

Interestingly enough, some people, including one factory tech I spoke to, recommend that you turn off ESP on heavy snow/slipperyconditions. ESP and Quattro are two separate functions which do similar things. Quattro, you can't turn off, and in most cases it works with transferring torque via center differential. ESP on the other hand, uses brakes.

What happens under really slippery condition is that your wheels constantly spin at different speeds. Your front right wheel might have full traction, while the front left wheel might not. Same with the rear wheels. ESP wants to make all wheels turn at pretty much the same speed. So ideally, ESP should correct these conditions by applying brake to each wheel with wheel spin. But when these conditions are permanent due to snow covered road, ESP can't handle constant wheel slip. It just blinks and doesn't work. You should just turn off ESP on those conditions. (Some newer cars have specially designed snow mode, which you can leave on)

Also ESP does not defy laws of physics. It helps to keep the car in line, but can't really do it when you don't have traction.

What I am trying to say is that, you probably have summer performance tires on your car. Yes you have tread left, but even with an AWD and ESP, if the tires don't grab the road, there is nothing you nor car can do about. So get a set of decent all season tires. If you drive in the snow a lot, then get a set of snow tires. It will make a night and day difference, and give Quattro and ESP a chance of working as designed.

 

Good info, very helpful. You answered a key question... I simply wasn't sure that ESP and quattro functioned separately. In hindsight, it's pretty clear that I should have turned off ESP. Well, as is happens, I made the same trip in similar conditions this week without a problem, though poised to switch off ESP. I spoke to my mechanic, who suggested thatgrit orice/snow build-up on the ABS wheel speed sensor may havecaused theearlier problems.A good wash-down of thecar between trips may have helped clear theproblem.Does thissound plausible? Thanks foryour comments.

 

ABS wheel speed sensor works by reading dimples on wheel hub and calculating speed based on how fast the dimples are moving. So, yeah it is plausible that if the dimples are covered with dirt/snow/ or whatever, it can trigger ABS sensor to not read properly and freak out the ESP. The dimples are part of the CV hub assembly right behind the wheel. I would imagine it is bit hard to clean the area but you can snake your hose behind the tire to spray around the hub.

I also travel up to Tahoe a lot on I-80. The worst that I had was when it started to snow on Truckee, and by the time I got to the summit on Westbound, there was about a foot of snow on the ground. People slipped and slided playing bumper car and a semi almost jack-knifed right next to me.AndI couldn't even stop to put the chains on because I would have risked getting stuck in the snow. (That's tells you how fast it was coming down.)

It took me 4 hours from Truckee to Colfax, and the Eastbound traffic was blocked off at Auburn. I stopped at Auburn to get a cup of Joe and had about 3ft of snow on top of my car. At the time, I did not even have my Audi with quattro, but I seemed to manage okay. And how you wonder? Tires... I was sure glad that I put on a set of nice tires a couple of months before the trip.

I really think that first thing to do is to have a set of good all season tires. Anyways, have fun at Tahoe. My A6 Avant might be parked next to your A4 next time you are parked in a resort parking lot.