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99' GC cutting out while braking


rgtiger70
08-28-2012, 10:17 AM
I have a 99' GC and just changed out the EGR valve. Now the engine cuts out when you brake or get to a low speed. Idles a little rough also. Any ideas?

RIP
08-29-2012, 02:31 PM
That's a good one. I'd guess it's vacuum related since both use it to function. Brakes use a vacuum operated brake booster. Check EGR vacuum line connections.

rgtiger70
08-30-2012, 07:59 PM
To add to this- the service light came on and the code was to say it was running rich in fuel. Any ideas?

RIP
08-30-2012, 11:53 PM
http://www.obd-codes.com/p0172 Again points to a possible vacuum leak.

rgtiger70
09-11-2012, 12:11 PM
Had checked out and said the vacuum system was fine, no leaks they found. Said they(mechanic) neeeded to checck out the main board to see what was going on with computer.

RIP
09-11-2012, 12:52 PM
With vacuum good next on the list is the Idle Air Control (IAC) valve. It trys to maintain a constant 800 rpm idle by opening a port in the throttle body downstream of the throttle plate. Anytime the throttle plate is closed meaning your foot is off the gas pedal, this port opens to control idle rpm. It opens further as you slow to a stop, turn on the A/C, turn the steering wheel, shift into gear - anytime there is a load on the engine when the throttle plate is closed. Many times that port gets clogged causing stalling and or rough idle. You may get away with just cleaning the throttle body and that port.

If it stalls with throttle applied then the IAC is out of the picture.

pentabob
09-11-2012, 03:57 PM
May want to try cleaning the throttle body, simple and cheap.
Good luck

edit....
oopps, sorry Rip, I just read the last sentence of your post, I agree, that should do it.
Bob

rgtiger70
09-20-2012, 11:11 PM
Had taken to dealership to get work done($500 later). Was told the idle control motor was burned out due to carbon build up. Had replaced and the engine cleaned(de-carbonized). A day later still having same issue, cutting out when idle gets low, running a little rough when driving- like skipping firing sequence. But no one mentioned anything wrong with the firing order. Still cant ffigure out, need help!
Thanks for any feed back.
Robert

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