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95 Chevy cranks excessively if sitting

n01tk

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I tested the IAC input with a noid light. The noid light flashes with engine running. Lights turning red and green if throttle is varied. Noid light does not flash when key is turned to on position. Also no flashes when key is turned to off position. Noid lights stay lit but don't flash either in "on" position or " off " position. Looks to me the ECM is not running the software routine to park the IAC for cranking? Comments please.
 

n01tk

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Removed IAC from TBI. Plugged port and started truck. Increased throttle, IAC pintle moved out, decreased throttle and pintle moves in. IAC appears to be working. Reinstalled in TB. Started truck. Removed PCV vacuum line, RPM initially increased but came back to near normal. Reinstalled line, RPM dipped but soon increased back normal. This verifies the IAC is responding to idle changes. I am picking up a PCU from local salvage yard. It doesn't have the proper BNKM prom but I can get one of e-bay for $39. Does the BNKM software vary from one vechicle to the next ( has to be reflashed for particular vech.) or is it generic?
 

THEFERMANATOR

FRANKENBURBAN
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So long as the 4 digit code matches, it is teh right PROM chip. Just make sure your getting teh right PROM for it. And new ones aren't readily available from GM for most applications as GM has discontinued them as they are WAY past the 10 year mark that they are required to make them.
 

n01tk

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Picked up the used ECM from salvage yard. No time to install. Truck seems to be starting quicker since I done the low idle adjustment procedure. Will keep you informed. Busy at job.
 

WarWagon

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Picked up the used ECM from salvage yard. No time to install. Truck seems to be starting quicker since I done the low idle adjustment procedure. Will keep you informed. Busy at job.
Enlighten us on the low idle adjustment procedure? I recall it being in drive with park brake on and wheels chalked...
 

n01tk

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Warmed engine up and waited for it to go into closed loop. Ensured IAC was fully closed and unplugged IAC connector. With truck in gear, brake applied, adjusted idle to 550 rpm. Shut truck down, plugged IAC back in and done the IAC reset ( for my year of truck), 10 sec with key on position, 10 sec key off position and than start truck. Engine idle is controlled at 700 rpm. Not sure if this is 100% right, but seems to have made a difference on start up.
 
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