ABS Problems

[reffittm]

Ok, I searched the forum before posting and could not find my exact problem, so here goes...

My ABS brakes (1996 Blazer) are making an excessive amount of noise when I am stopping, even on dry roads. I know the normal sound of them, and this is excessive.

Also, my ABS light came on and is stuck on.

And, the truck revs forward then slows violently a couple of times as I am speeding up (for example, it revs to 3700 rpms before trying to shift and then jerks the car back as it goes down to 1000 before shooting up again). It feels like trying to accelerate with someone stepping on and off the brakes.

I took the ABS fuse out and the acceleration jerks went away, but then my regular brake light came on as well and even though it seemed to accelerate ok, it felt like the damn thing was pulling a loaded trailer behind it the whole time...like the brakes were slightly stuck or like driving with the parking brake partially on (I checked and the P-brake was fine).

Then, I put the fuse back in for the hell of it and the car was fine!!! Absolutely perfect for about 30 miles and both lights were off. Then I slowed down and heard my ABS overworking again and the light came on and the acceleration jerking started again.

Any ideas???? Please help!!!!

[reffittm]

I went to Autozone and asked them if there was anything I could at least examine before taking it to a mechanic, but the guy was not really very helpful. Also, he said that there is no way that they can run a scan on an ABS light...only for "Service Engine". Is there any way I can find the codes myself without taking it to a mechanic?

Also, I read in another thread with a problem that is SOMEWHAT similar to mine that I could clean and reinstall the SPEED SENSORS. I am a novice so it would help me a great deal if someone could explain to me how to do this. I want to do as much as I can before I send it to a shop.

[rlith]

More than likely it's one of your sensors if the light is on. 1st thing to check is that the connectors on both sensors are actually hooked up. (follow the cable from each sensor to the frame where the connector is) Also pull both wheels and check for debri in the gear. As I said, it's most likely just a sensor.

[mike2004tct]

From the description above, I'd guess a stuck caliper on the front, but more likely a bad piston/cylinder on the rear. (No mention of the truck pulling one direction or the other, suggests a stuck rear brake).

It could be a sensor, but why would that cause the brakes to be on?

If the problem exists after checking the sensors and cleaning the sensors themselfs, start looking at the calipers and cylinders. Might even be a jammed parking brake mechanism.

[reffittm]

So, last night I looked at everything on the front wheels, cleaned up my brake parts with brake cleaner, and popped the fuse back in and the ABS light once again went off. I drove it about 20 miles and it was perfectly fine. My wife drove it to work this morning and it was fine. I'm worried that it'll come back though, because this happened before as well. Is there any why to clean the sensors without taking the hubs off?

[blazee]

http://www.automotiveforums.com/vbul...d.php?t=425516

[reffittm]

Hey blazee, that service bulletin was awesome! How can I get my hands on those???

[reffittm]

Well, I checked the sensors and they are fine. The car ran fine (no problems or lights at all) most of the day yesterday until it finally started acting up again. I hit the brakes to turn and the ABS started working again for no reason (roads were completely dry) and when I started to speed up it revved up to 4000 rpms before shifting then lurched back forth a bit before finally going.

I disconnected the three harnesses on my ABS computer to see if that would just disable the ABS and allow me to drive. But, even when I did that, the damn acceleration problem was still there. It's almost like a transmission problem, but then why would it only come and go with the ABS problem? I mean, it was perfect until the ABS started acting up again, then it immediately started that acceleration problem again! This sucks!!!

[reffittm]

I checked the vehicle speed sensor as well and it was pretty dirty with metal shavings and grease and crud. I cleaned it, checked it, and reinstalled it. Also, I checked the voltage going to it from the harness and it was 5 volts. Thought this would fix it but it happened again. Seems to be activated when traveling over 20 miles at one time. HELP!

[reffittm]

Ok, here was the solution...

I finally got the ABS light to come on (it was an intermittent problem) and took it to a local shop that put it on the computer for 35 bucks. It read that it was the left front wheel.

I got a new sensor and backing plate for 100 bucks and replaced it. The old sensor had been torn up from a rock that was stuck on the hub and slightly rubbing between the sensor and hub.

However, this didn't fix the problem (but this may have been a potential problem anyway)!!!

So, I just went ahead and bought a new VSS (vehicle speed sensor) and installed that last night (it took only 5 minutes). It seems like that finally fixed it.

That acceleration problem I was referring to had something to do with the speedometer. The transmission was searching for the right gear but couldn't find it since it didn't know how fast the truck was going. Also, that VSS appears to operate the rear ABS. These two problems combined are what led me to the VSS.