This must be one of the V6 models as they appear to be the only ones with a PCM controlled canister purge solenoid. This vehicle has a four wire IAC stepper motor that has power and drive provided by the PCM.
Assuming it will even communicate via the ALDL, I would hook up a scanner to it, KOEO, and tap that PCM. Do any of the values change when I'm tapping on it? If I could get it to run, I would also tap it while it was running -- will it stall/run worse?
If I found the PCM was responsible for these behaviors I would disconnect the PCM connectors and check the ohms for all the solenoids, coils, and motors (and their circuits) that are controlled via the PCM to make sure one of those isn't wacking the PCM. If I found any unusual readings I would disconnect that solenoid/motor and see if the PCM behavior returns to normal. In this event I would affect a repair and advise replacement of the PCM due to potential damage. If the PCM did need replacing, I would also confirm the powers and grounds to it, and be done with it.
ckp sig was good to the pcm, but no est out, changed the computy but didnt update prom, car runs fine, sadly the heater core took a dump right after, dont know what took out the pcm , it was a budget job. the evap sol seemed to always be on with both pcms, supposedly duty cycled but no duty from either pcms. erratic iac behavior stopped after changing the pcm.
other 2.8's that come in have the same warm evap sol , so i assumed it was ok or almost time for the POS to go
the cool thing to watch was the comp ground going out of whack when the sol and iac was twitching the ect would drop out with each actuating pulse, it was awesome.
First of all, it's extremely cool reading your posts (and everyone else for that matter) - even the 99 slang like "computey" and "budget job". Hell, as I read all of these posts from everyone, it sounds like that crazy 99 teacher. :--)
As far as the 2.8 purge sol, it's supposed to "always be on" as it is DE-energized to purge. IOW, the sol is energized any time the engine is running, then de-energized to allow purge. A common strategy from the General on purge solenoids and some EGR solenoids.
Again, great job on these posts, and it's great to see you guys "in the trenches".
