Mechanics

WHY IS MY 07 TRYING TO STALL WHEN BRAKING?

2007 Chevrolet Colorado • 130 miles

This began with starting. Would crank then try to die but catch back up. Replaced plugs and that seemed to help. Then it started again but seems to be worse when braking. Braking to make a turn the engine will try to die then pick back up and will do this repeatedly until you get off the brakes and apply the accelerator again. Runs smooth down the road and doesn't miss at idle. Problems seem to be only at first start up and when braking. I am also having to replace ABS wheel speed sensors on the front as they were damaged when replacing rotors. Could this have anything to do with the problem. I can't remember if this started about the same time. I know the stumbling at the starting was before the wheel sensor problem but the braking problem may have started about the same time. Wondering if the circumstances could be related?
Thanks!
Joe
Avatar
LiLRascal
February 21, 2012.



The ABS sensors should not be related to the poor idling.

If the engine idles correctly when the brakes are not applied, then you most probably has a leak in the brake vacuum system and this is causing a vacuum leak which can cause erratic idling.

KHLow2008
Feb 21, 2012.
I replaced and repaired the ABS wheel speed sensors but the ABS fault light is still on. The vehicle will stumble at cold start then smooth out but will stumble again when you pull it in gear and nearly die but not quite. After that the stumbling only occurs when you are breaking for a stop or turn but as yet has not actually died. It is getting worse, however, and am expecting it to start dying anytime. Not very familiar with this vehicle. Where would you look for the vacuum leak? KHLow2008's response makes a lot of sense as I have experienced this with the older models which I am more familiar with.

Tiny
LiLRascal
Feb 22, 2012.
The additional information indicates you have a fault with the idling system and I would suggest starting with cleaning the idle control system which includes the throttle body and IAC.

For the ABS fault, what is the trouble code?

KHLow2008
Feb 22, 2012.
Will try that and thanks! As for the fault code I am not sure as yet. Haven't had it checked. I'm old school and my old ways of retrieving code doesn't seem to work with this vehicle so have been taking to a mechanic to diagnose. Can I determine code with out scanner? I am guessing it is the wiring as it was broke on the driver side and I have tried to splice it. Had to replace passenger side with new one so I would think that one would not be the problem? Maybe good but can't get lights to go out. Tried to remove battery cable but that didn't work or the light came on immediately with starting.

Tiny
LiLRascal
Feb 22, 2012.
Without the fault code, you would be working blindly and replacing things that are good on a trial and error basis.

KHLow2008
Feb 22, 2012.
Yes, I understand that. Will soon be going to my mechanic friend and let him check the codes. Thanks Again!

Tiny
LiLRascal
Feb 22, 2012.
Ok guys, When this brake trouble originally started I pulled the ABS1 and ABS2 fuses hoping to kill the system and fault lights. I would have been completely happy with that. However, that didn't work. I have went back and repaired the system but the lights stayed on. Had it checked by a mechanic friend and the components checked ok and the brakes were working and found code 201. Finally determining the code was electrical problem with abs fuse #16 I checked that out and found all was well. But I noticed the 2 missing fuses and remembered what I had done. Replaced the fuses, started up, the lights went out, yea! Wrong. When starting down the road and applied the brakes considerable vibration in the brake pedal, scrapping-grinding sounds, a pumping vibration sound like an electric fuel pump, then all noise quit and the lights came back on. Brakes still work. It was dark and haven't checked fuses yet but my question is should I taken it through a reset process of some type? Any thoughts? Thanks!

Tiny
LiLRascal
Mar 8, 2012.
The pedal pulsation indicates the ABS is working at that instance.

Since the ABS indicator light is back again, check the trouble code again and let me know what it is. You can try resetting the code and retest.

KHLow2008
Mar 8, 2012.
I haven't had a chance to recheck the code, however, when we went out this morning and started up the light went out again. When we started down the road and hit the brake all the ruckus started again. Pushed the pedal a little harder the light came back on and all the racket etc. Stopped. We stopped for something and when we started back up again same thing, light out, racket, light off. Craziest thing I ever came across. Will check codes at first opportunity and report. Thanks!

Tiny
LiLRascal
Mar 9, 2012.
When the light comes on, the ABS system has been disabled, therefore nothing to alarm you.

I believe you have a fault with the ABS master pump ( modulator itself).

KHLow2008
Mar 9, 2012.