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Hi all. I'm having some trouble with my new to me caddy. I recently posted that my distributor went south and I needed to replace it. I'm still struggling with the timing but I'm getting closer. The distributor has all new components and is drop in ready. The reason I'm having trouble timing it is the idle won't stay steady when warm. When cold car starts right up and idles @ 800 rpm. When warm and I can get it to start the idle drops and fluctuates between 500 & 700 rpms. I also noticed that rpms surge when I hold my foot steady on the gas pedal at any rpm. I pulled the following codes from the dic: p031, history, shorted map sensor, p053, history, distributor signal or reference signal interrupt from icm, p065, current, sps signal problem (cruise control). Also the flange rotted off the "y" pipe so currently there is no exhaust connected. At first I thought idle control motor then started to think fuel pressure regulator but now think it may be wiring or pcm? what do you all think? thanks

Edited by trashtruck
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Since the vehicle starts and runs fine in open loop, & the flange rotted off the exhaust I would suspect the computer is wondering what to do, since there is no o2 sensor information when the engine should be in closed loop. 

Correct the exhaust problem and retest. The engine needs exhaust flow, including some kind of back-pressure to wake up the o2 sensors. Clear the codes before you restart the engine after the exhaust repair so you get fresh information.

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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When you are working on the exhaust you will be glad it is NOT the North*. 

Good job finding the vacuum leak :shaka:

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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Was going to suggest vacuum leak, glad you got it. Sure sounded like a leak. That idle was too high. your idle now is normal

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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