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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), GMC Mechanic
Category: GM
Satisfied Customers: 29427
Experience:  GM Grand Master Technician 2007. 14 years experience.
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Im ***** *****. Had the alternator replaced in my 2002

Customer Question

Customer: Im ***** *****. Had the alternator replaced in my 2002 envoy. It used to idle at 1000 rpm. Now it Idles at 500 roughly and I got a ck engine light and the smell of burnt something in the cabin.
JA: Thanks. Can you give me any more details about your issue?
Customer: Wife reports a "engine Stop" light but I didnt see it or the :Check Engine " light. Vehicle has 170k and runs otherwise well.
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Submitted: 10 months ago.
Category: GM
Expert:  GM Tech (Cam) replied 10 months ago.

Hi there, I am Cam. I Am sorry to hear about this issue on your vehicle.
This is a common issue on the 4.2L engine. What happens is the system was likely reset because of the battery being remove. Then when it was hooked back up, the adaptations it had learned specifically for the throttle have been erased. To correct this, take the upper intake plenum off, the black box that says 4.2L Vortec. There are 2 10mm bolts and 2 hose clamps. Then clean the throttle plates with a rag and carb cleaner. After that, take the battery cable off and reset the vehicle. This should fix this.
Take the battery cables off the battery, hold the ends together for 10 seconds then attach them to the battery and see what happens. This will reset the whole vehicle. And the reset is more about touching the cables together when removed from the battery than having them removed. touching them together its what drains the capacitors and resets the short term memory.

Customer: replied 10 months ago.
Wow. Touch them together. I'd never have guessed. I did notice the seat and mirror memory was different than before.
Expert:  GM Tech (Cam) replied 10 months ago.

Did that change them?