I am getting a code P0507 but notice my idle fluctuates from 800 to 1200 when my compressor comes on. My compressor comes on while the fan is on wheather heat or cool Any suggestions out their. The IAC valveis suggested in the book but the vehicle runs ok otherwise.

 

I was getting codes p0107, p0507 and p0304 on my 98 Blazer. I cleaned everything possible. Used Seafoam in the gas and fixed the P0304. It took 2 days to find a vacuum leak in a 7/32 line going over the brake booster (out of sight). The line had a slit in it, like it had parted where it was seamed together. this line runs from the manifold to the fender, drivers side.
magnaman13

 

Magnaman13 did fixing that 7/32 line fix a code? If so what code? Do you know where the line that goes into the driver side fender goes to? Thanks Bernie11

 

All codes are fixed and my idle is smooth again

 

I have no idea where it goes. It connects to a hard line at the fender

 

That vac line goes to a vac reservoir inside the fender in late nineties.
Classic symptom of that leak is heater output goes to def when accelerating.
You have high idle because of a vac leak, that is why the code, the IAC is unable to control idle.
Compressor may run in Def, heat/def or either ac mode. Turn to 'vent' it should not run.

With warmed engine disconnect lines at intake one at a time and plug port with finger, when speed drops.. follow that line

 

Thanks a lot. I will give that a shot this weekend. Again thanks Bernie11

 

My p507 problem looks to be a cold weather problem. The only time the code shows up is when the temp drops bellow 40. Its hard to duplicate in the summer months. My gut feeling is that one of my vaccumm hoses has a leak. Motor runs fine. IAC valve looks to be easy to change but just dont feel its bad. I guess I have to wait to fall to work on it. Sorry that I am not more helpful. Just a book mechanic. Just read up on the problem and enjoy trying to fix it.