Piston Slap: The Sable's Spurious Speed Sensing?

Sajeev Mehta
by Sajeev Mehta
piston slap the sables spurious speed sensing
Longtime TTAC Commentator Golden2husky writes:

Dear Sajeev:

I have a problem with my old ’92 Sable. About a year ago the ABS started to lightly engage while the wheel was turned hard left or right as you pulled into a parking spot. The parking was not at “turtle” speeds but was well below the need to engage ABS. This issue began to get worse after a few months; the unwanted ABS engagement would occur with less of a steering wheel angle. No longer did you need the wheel fully turned to cause the problem.

For the last two months the car sat unused, but now with the potential for snow and the need to haul building materials on the roof rack I’ve begun using the car again. Now, with the wheel pointed straight, the car will occasionally engage the ABS when stopping at a red light. Usually the engagement is light, but a few times it was pretty severe. I’m concerned about rear-ending somebody. I do not consider disengaging the ABS to be an answer. The ABS idiot light comes on at startup and extinguishes after a few seconds.

You have a lot of experience with old Fords so perhaps this has happened to you. The car is nearing 200K and has spent its entire life outside. Salt use in these parts is pretty moderate. Tires and struts are fairly recent and are in excellent condition.

Sajeev answers:

I stop in my tracks and assist any Sable in need, as the original’s radical design inspired my childhood … while the decades-long decline inspired my career in automotive journalism.

So Sables are indeed worth the effort, but I digress … this bizarre ABS action is from a wheel speed sensor out of whack, giving readouts significantly different than the other three sensors. This discrepancy is a huge red flag for ABS, causing it to take corrective action. And as the sensor fails to a greater extent, I reckon less steering angle is needed to create a ABS-sensitive speed discrepancy.

I’d recommend the free repair first: remove all wheels, inspect each tone ring for corrosion or missing teeth, clean both the ring and the sensor (with brake parts cleaner; use more aggressive stuff if severely corroded) to ensure a strong connection.

If that doesn’t work, you must use a code scanner for ABS codes, not the cheap one (or the paper clip trick) for Ford EEC-IV trouble codes. Finding a mechanic with the right tool and 30-60 minutes of their time is worth it: from there the sensor(s) are dirt cheap online and an easy DIY repair.

Conversely, since steering angle is the concern, odds are one of the front sensors is busted. And since they are so cheap, you could buy two and solve the issue for less than the diagnostic time from a shop.

What say you, Best and Brightest?

[Image: Ford]

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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2 of 26 comments
  • StudeDude StudeDude on Jan 18, 2019

    Because of the age of the vehicle, OBDI and the low cost of the front ABS sensors, I agree with your approach to replace both sensors. Also check the routing of the sensor wiring and the connectors based on the occurrence of a fault while turning. One of those cable routing brackets may have come loose or rusted away.

  • Pwrwrench Pwrwrench on Jan 18, 2019

    Yep, I vote for the $64 for the two front sensors,AFTER checking the tone rings for damage or contamination (and the wheel bearings). Wear particles from the rotors and pads can fill in the teeth on the ring giving an incorrect signal to the ABS control unit.

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