Thanks for tables helps alot

I do have a small basic scan guage in truck so temps are from the scan guage also I monitor vacuum all good there as per scan tool and target as per GM

....the table with Target Idle speed vs idle speed is exactly what it does when it works correctly 525rpm in gear once it gets to 130* but when it does not it has to get to at least 190*

The other table not sure I understand it, shows start up idle speed run time vs coolant temp .....


Again thanks for all the input it helps

 

What is your idle vacuum once at temp?

 

Will check again later today ......cold here today so will check vacuum as it warms up and full warm and advise , TKS

 

OK cold today 10*F outside truck has been sitting since yesterday

after initial start with 1000rpm idle for about a minute maybe less came down to 800rpm in park 700rpm in gear ........did not come down to 525 rpm till ECT got to 192*f

lowest Cold vacuum ( below 132*f) in gear 17.1 @ in park 19.1 vaccum at all times did not fluctuate more than 2/10

Once ECT got past 132 it started to move up by 170* it was vacuum 20 hg in park 600rpm in gear 18hg @525rpm

So fully warmed up Vacuum in Park @600rpm 20hg in gear @525rpm 17.9-18.0hg

Your thoughts ??

 

Idle vacuum sounds normal in both park and gear for those RPMs with stock cam.

 

Yes seems all good to me too ........ at this point once the weather warms up it wont be a problem til next winter but really want to figure out
........I will pull the MAF right off and clean well TB has been done twice ? after that all I can do is throw parts at it ........tech a dealer is stumped too told me to change ECT sensor and T-stat but only a guess ......there is a TSB for the TPS unit on these trucks but you must throw the 2135 code beofre they will change it but I have no idea if the TPS would cause this am told TBS usually cause rough and very high idle and does not return to normal in warm weather ?? Other than that truck runs great

 

Help ......... bringing back this old thread ..............the problem is back now that cold weather here .......same issue did change the coolant temp sensor and T-stat ......no change ?? really stumped .. after cold start fast idle in gear at 800 rpm wont come down to 525 til coolant temp at 192-195 ........must be other parameters (iat ??)that control this it seems to get better as weather warms up eg fast idle comes off around 168 F when outside temp at approx. 40 but at 20f or colder it wont come off til 192-5f any thoughts

 

Ever clean the maf?

 

Yes but been awhile . cleaned TB more ............will clean MAF and see if that helps