Noise and modulation on low speed stops

[Jand3rson]

Is that one of the 3 big square ones under the hood, near the strut tower?

[PiercedE30]

I believe the three are the main, fuel pump, and abs (?). Not sure though. Either that or unplug the plug on the pump and try it.

[Jand3rson]

I also noticed something else about this problem today, it only seems to do it under very low speed light braking, such as in parking lots or rolling up slowly to a light. If I really jam on them, or if I'm braking hard around a corner or something, they're fine.

[Bmjpv]

abs

I had this at low speed too. Fixed it by finding and replacing the ABS counter on the axle. It can only be the counter or senor for at the corners. I hope my repair helps with your hunt . Joe

[gearheadE30]

My car did this a bit but there was a fuel injector retaining clip stuck to one of the front ones that was causing it ;). I have no idea how that got there...

At any rate, I think that it is on the sensor end of the ABS system. Have you checked them with a scope yet? Is all of the wiring good, including all connections? It almost sounds like one of the sensors is failing and causing the sensor to get a flat reading.

[Jand3rson]

So I can't say for certain, but I think I *might* have fixed it.

A month or so ago when my fuel pump took a shit, the first thing Crivvy told me to check was the fuel pump relay, one of those 3 in the block next to the strut tower. He also said to maybe try reversing them, and see if it does anything. Well, I think I left them reversed, and while I was just getting gas, I swapped them, and now the problem seems to be gone. One of them also wasn't even all the way seated, so who knows.

[DaveSmed]

So I can't say for certain, but I think I *might* have fixed it.

A month or so ago when my fuel pump took a shit, the first thing Crivvy told me to check was the fuel pump relay, one of those 3 in the block next to the strut tower. He also said to maybe try reversing them, and see if it does anything. Well, I think I left them reversed, and while I was just getting gas, I swapped them, and now the problem seems to be gone. One of them also wasn't even all the way seated, so who knows.

Interesting that one wasn't seated, but none of those are the ABS relay. On your car, it is located under the dash above the ABS module clipped on to the bracket the module mounts to.

Those three relays are the main relay, which powers the fuel pump relay, injectors, DME and ignition coil. (May vary slightly based on i vs e engines)
The fuel pump relay which powers the fuel pumps (imagine that.) And the O2 sensor heater relay.

[Jand3rson]

I'll have to check those, because now it's back, and doing it worse than ever. Andrew and I are going to see if we can't track down the problem this weekend.

Autocross is in 2 weeks, and I can't race like this!

[AndrewBird]

I was just remembering, back when we did all that work to your car in Portland, one of the connectors in the engine bay for one of the sensors got melted a bit because it hadn't gotten plugged back in. I wonder if it is shorting out? Have you checked all the wiring to and from the sensors yet?

We also should check the rear sensors. If the fronts were covered in stuff, the rears are likely to be the same way.

[Bimmerman325i]

Sorry for the bump, but my car decided to have this same problem on the way to work this morning. Did you ever solve the problem? It's never done this so I'm a bit confused; I didn't even know the ABS system worked until now, usually I can lock up a tire under braking. I've got a driver's school coming up soon and I definitely can't have this problem linger! Please Help!