1990 Buick Century, Computer Codes & Rough idle

My car a 1990 Buick Century with 70,000 miles on it over the last few days has developed a rough idle when hot, and stopped at a red light the car fights not to stall....
When I drop the car into neutral or park the idle corrects itself and is barely noticeable...
The exhaust on my car seems erratic, and is making a put-put-put sound from the muffler...
A friend of mine did the paper clip trick to get the computer to spit out two stored codes... they were 12 (I know this means the computer is working) along with 15 and 48.... can anyone identify these codes and suggest what could be causing the muffer to make the put-put-put sound.... it almost sounds like muffled bubble wrap...
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Code 15 indicates there is something wrong with the coolant temperature sensor. Perhaps a bad connection or bad sensor.
Code 48 indicates a misfire. Check plugs, fuel, compression, etc.
Steve

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On Fri, 20 May 2005 17:22:09 -0400, "Steve Mackie"

Steve,
Thanks for the reply, my mechanic cleaned out some hose on my engine, said it was loaded up with carbon... it runs better, but not much better.... he also said that my 6th plug/cylinder fires weak but he also checked the fuel injectors and they were fine... if i change the plugs and wires, think this will create an improvement or a waste of time?
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Re: 1990 Buick Century, Computer Codes & Rough idle Group: alt.autos.gm Date: Sat, May 21, 2005, 4:48am (CDT+5) From: snipped-for-privacy@hell.com (grimreaper) On Fri, 20 May 2005 17:22:09 -0400, "Steve Mackie"
Code 15 indicates there is something wrong with the coolant temperature sensor. Perhaps a bad connection or bad sensor. Code 48 indicates a misfire. Check plugs, fuel, compression, etc. Steve Steve, Thanks for the reply, my mechanic cleaned out some hose on my engine, said it was loaded up with carbon... it runs better, but not much better.... he also said that my 6th plug/cylinder fires weak but he also checked the fuel injectors and they were fine... if i change the plugs and wires, think this will create an improvement or a waste of time?
It might make a difference if it is the plug or wire that is and and not the coil ..Did he clear the codes and did any of them come back? S Cook
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none of them came back.
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