Issue with ABS (I think)

[spiderw31]

The car is a '92 GP coupe, LQ1 with ABS. With that out of the way, here is the issue. About five or six times now (three of which were today), it seems the ABS is kicking in with no wheel locking. The pedal goes hard, I hear the the solenoids / motors operating, and the brakes go to crap. Each time this has happened, it has been on dry ground at low speed, and nowhere close to lockup. The only interesting bit is that each time this happened, I was either entering or exiting a turn, i.e. turning the steering wheel. No ABS light ever, not even during the episodes, and at all other times the brakes work fine (ignoring uninspiring stopping power, but thats something else altogether).

 

My initial suspicion is a front wheel speed sensor or associated wiring, but would definitely appreciate assistance in where to start chasing this down. Has anyone here had something like what I've described?

 

One last question. Since the brakes are completely functional at all other times and there are no warning indicators for the ABS or brake system in general, and I'll probably not have time or location to troubleshoot for a bit, I'm thinking of pulling the ABS fuse temporarily. I know I'd have a regular non ABS setup (going into winter no less), but are there any other reasons I should avoid doing that?

[RobertISaar]

ah, the joys of a properly functioning ABS-VI setup..... i don't think i've ever had them working quite correctly.

 

anyways, i'm fairly certain at least one of the guys that autocrosses with an ABS-VI setup has the same problem. it might have been Adam? or Andrei? ???

 

anyways, pulling the fuse.... i don't see anything bad happening from it, you may get a constant ABS light?

[jman093]

Definitely sounds like a WSS is failing. Gotta love how that system operates on the principal that ditching all your braking capability will keep the wheels from locking. The system is VERY slow responding as well. If you don't want to figure out which sensor it is, yes, you can just pull the fuse. No ABS obviously and the ABS and brake lamps will be on, but nothing else will be affected. I actually think it was the relay, not a fuse, I pulled in my old GTP when autocrossing. The ABS-VI simply cannot function properly in that environment even if nothing is broken. I put it back in afterwords just so the lights would be off. I always dreamed of converting that car to the 2nd gen GP's Bosch 5.1 system.

[Schurkey]

The single problem I ever had with the ABS on my '92 and '93 Luminas was a corroded wire harness on the right front, that connects to the RF wheel sensor. The sensor itself was fine, but the harness had gotten water (road splash) inside the insulation and the copper wire was totally green about a foot or more back in the harness. I kept cutting and cutting, trying to get to copper-colored copper, so that I could solder in the new pigtail.

 

The pigtail was $24, tremendously expensive for a foot of wire and a molded end; but whatchagonnado? Easy (if frustrating) to fix. Car's been working fine for a couple of years now.

 

Uninspiring stopping power? No actual problem with worn pads, and the park brake works OK? Easy diagnosis, moderately-easy fix. Put a brake booster in it, the one you have is toast.

Edited December 14, 2013 by Schurkey

[Cutlass350]

The system is VERY slow responding as well.

Hmm, in that case, humans should never be allowed to drive.

 

If by "very slow", you mean that it takes ~1/10th second to respond to a lock up or a potential lockup, then yes. The Delco-IV system is "slow". But, the Delco systems were never ever designed for performance braking. They were designed for common driver braking problems/emergencies - like ice, snow, dirt, mud, etc.

 

Considering that I owe my life to a Delco-IV ABS system, I would say that the systems do and have done very well. Gee, after 15-20+ years, some systems need maintenance - people should be so lucky with all of the automotive systems.

 

FWIW, unless people have driven on roads with snow covered ice, then they can't talk about how ABS is not needed.

 

Human brake reaction time

[Cutlass350]

The car is a '92 GP coupe, LQ1 with ABS. With that out of the way, here is the issue. About five or six times now (three of which were today), it seems the ABS is kicking in with no wheel locking. The pedal goes hard, I hear the the solenoids / motors operating, and the brakes go to crap. Each time this has happened, it has been on dry ground at low speed, and nowhere close to lockup. The only interesting bit is that each time this happened, I was either entering or exiting a turn, i.e. turning the steering wheel. No ABS light ever, not even during the episodes, and at all other times the brakes work fine (ignoring uninspiring stopping power, but thats something else altogether).

 

My initial suspicion is a front wheel speed sensor or associated wiring, but would definitely appreciate assistance in where to start chasing this down. Has anyone here had something like what I've described?

 

One last question. Since the brakes are completely functional at all other times and there are no warning indicators for the ABS or brake system in general, and I'll probably not have time or location to troubleshoot for a bit, I'm thinking of pulling the ABS fuse temporarily. I know I'd have a regular non ABS setup (going into winter no less), but are there any other reasons I should avoid doing that?

 

 

If you yank the fuse, then you have regular brakes. I had to do that on my Delco IV system two times so far.

 

I had a similar problem. For the front tone rings, use a brass "tooth brush" (get them at Home Depot in the plumbing section), and get the rust of of the tone rings on the front axles. Also, clean any rust/build-up from the tip of the ABS sensor on the front. Also, check for any broken teeth on the tone rings.

 

Otherwise, you have a few options:

1) Bring it to a Dealer, and they will be able to log the wheel sensor speeds, and determine the bad sensor.

 

2) Make your best guess as to what's wrong. It could be a sensor, broken tone ring, hub (rear), or bad ABS control unit. You will likely end up replacing unneeded parts. But, it may be cheaper than a dealer. BTW, there are a TON of fake wheel bearings on the market. I got screwed by buying "Timken" bearings from an ebay seller. Yes, they work for ~3-9 months, then they go bad.

 

3) Yank the fuse, and drive without ABS.

 

Good Luck!

[Cutlass350]

BTW, there are many possible problems in any complex electro-mechanical system (e.g. ABS, EFI, etc). Sometimes, a good guess can be made to the problem. Sometimes, the problem can be solved by a few good guesses.

 

However, the proper and correct way involves diagnosing the error.

 

Below, you can see a capture from my scanner that shows that the LF-Feedback current sensor was seeing current, when it should not be seeing current. I changed the ABS module, and fixed the problem.

 

 

 

So, a mechanic/person with the real and proper tools can diagnose the real problem with the Delco-IV ABS system, and not have to keep guessing.

 

Good Luck!

[spiderw31]

Uninspiring stopping power? No actual problem with worn pads, and the park brake works OK? Easy diagnosis, moderately-easy fix. Put a brake booster in it, the one you have is toast.

Yeah, I've read your thread from a few years back, and I'm pretty sure that's one part of the issue. The Wearever pads currently on the car being the other . Both need to be changed!

 

FWIW, unless people have driven on roads with snow covered ice, then they can't talk about how ABS is not needed.

Been there, done that, many times. I'll say this though; ABS helps a lot of times, but I've been in far more that one situation where I was cursing the presence of ABS when on snow covered roads.

 

Thanks to everyone for the input thus far. Joe, I hear you on getting a proper diagnosis. In my area though, I could make a couple wrong guesses and still make out ahead of what I'd be paying a dealer to sort it out, so that's a very tempting way to go. I'm thinking I'll do a thorough check to the best of my abilities and see if that turns up anything with certainty. After that, I can better judge whether a dealer is the best route.

 

At this point, I'm still suspecting the issue is in the front, since it has only happened when turning the wheel, or at large front wheel angles.

 

Oh and FWIW, I agree with you Jesse; compared to more modern systems the Delco VI system is slow (though that's kinda the way it is with technology pretty much across the boards:lol:), and I wouldn't want it active in a competitive setting either. I can totally see it deciding the best course of action would be to put me into a wall at some point! On the street though, it's generally not bad.

[Cutlass350]

In my area though, I could make a couple wrong guesses and still make out ahead of what I'd be paying a dealer to sort it out, so that's a very tempting way to go.

I agree. Plus, if you're planning on keeping the car, then replacing the rear bearings are mainly maintenance.

 

I'm "pretty sure" that you don't have the ABS enclosed in the front hubs. In that case, a visual inspection of the sensor tip and the rings is all you likely need. Since you do not get an ABS error when you start the car, or drive for ~0.1mile, that rules out a completely bad front sensor or tone ring. Again, build up of crud is often the cause of what you're seeing - an easy fix.

 

But, at the same time, since you do not get an ABS error when you start the car, or drive for ~0.1mile, that points to something that is marginal. If it's not crud build up, it could very well be weak/worn ABS motors or solenoids. Again, you likely can get a used on on ebay for under $50, and then try that. It requires that you bleed the wheels and the two ABS/MC bleed screws.

 

 

 

Been there, done that, many times. I'll say this though; ABS helps a lot of times, but I've been in far more that one situation where I was cursing the presence of ABS when on snow covered roads.

?????

 

ABS is not traction or stability control.

 

ABS works only when the brake pedal is pushed.

ABS works only when

A) One or more tires are locked/skidding

or

If the rate of deceleration of the tire exceeds the physical limitations of the braking system and tire to maintain traction.

In other words, the tire is slowing down so fast, it has lost it's grip on the road/surface.

Or, if the rate of slip exceeds the physical limitations of the braking system and tire to maintain optimal braking.

 

 

NOTE: ABS really does **B**. It rarely does A.

From a control theory point of view, doing only A would be very stupid.

 

The library at MIT has well over a hundred different books on just Control Theory. I never bothered to count. Any decent College that offers at least a BS is Control Theory also likely 50+ different books on Control Theory. Then, there's "Digital/Computer/DSP" Control Theory.

 

 

It's really B that makes ABS so good. Plus, the ability to control wheel independently.

 

So, if people are complaining about ABS and it effecting their braking ability, it's because the ABS is imho saving their *ss from loosing control of the car from having one or more tires lock up.

 

 

 

Again, the Delco system was never designed as a performance braking system. It was designed to be low cost, and optimized for real-life typical driver braking situations. It's not designed for the track - far from it. Imho, it's horrible for the track because it's very conservative on the braking ability of the car, and it is "slow" for braking and optimal braking during turns above 40mph. Also, the motors, gears, solenoids, seals, are not designed for any where near that type of "duty cycle"/repetition/re-use rate.

 

Even the (imho best ABS system) Bosch ABS system often needs replacement every 1-2 years with track use. Where for typical use, it'll likely out live the car.

 

 

Good Luck!

Edited December 15, 2013 by Cutlass350

[Cutlass350]

Doh............

 

I just thought of this.

 

CHECK YOUR TIRE PRESSURE!

 

Also, ABS **REQUIRES** that ALL FOUR TIRES ARE EXACTLY THE SAME WITH EXACTLY THE SAME WEAR.

So, if you have mixed or new tires on the front/back, that will also cause exactly what you're seeing.

 

The only exceptions are for factory cars that come with different front/rear tires (e.g. Vette). In those case, those tires must be the SAME MODEL, TYPE, WEAR, and have the PROPER air pressure.

 

In general, ABS can tolerate an ~~3% difference between the max/min tire size/rotation out of all 4 tires.

 

If people go by the tire diameter on Tirerack to determine tire size, realize that those diameters are based on a specific rim width and tire pressure. And, manufacturing tolerances can easy be 1-2%.

 

That's why it's REQUIRED to get all 4 tires replaced at exactly the same time with exactly the same tire on all 4 tires.

 

The above is not to say that people, like me on my Mustang , are not able to go with different size tires. But, I carefully choose my tires/manufacturer and rim widths to work with my Mustang's ABS.

 

Good Luck!

[spiderw31]

Crud or degraded wiring is my first guess at this point, as the car is low mileage (56000), and is generally very low wear. Age of course acts upon the rubber and plastics though no matter what. The tires are good too; roughly a year old, all matching, inflated properly, and with roughly 3k miles on them

 

Joe, while I definitely appreciate your help in the diagnostics department (you clearly have knowledge and experience), I don't particularly like the apparent condescension in explaining ABS. I'm well aware of what it does and the theory it operates on, and the many ways it is beneficial in daily driving. Perhaps I misunderstood what you were getting at, but what I was saying is that there are edge cases when ABS is not beneficial, and I've been in those situations. I will add to my statement though to mention that those times were far and away the minority, but edge cases do exist. And yes I know that the system wasn't designed for competition (see the last comment in my previous post). Please realize that I do appreciate your help in how to track down the trouble, I just don't like (apparently) being presumed an idiot.