1982 C20 Sluggish and High Idle Stuck

[82silvy]

I have a 1982 Silverado C20 with the 454, automatic, 2wd.  It has about 220,000, but engine and transmission have both been rebuilt in the last 40k miles.  The truck now is getting stuck in high idle when I start it.  I found that the TCS Solenoid isn't completely connected (one port is broken), but other than that I can find no vacuum issues.  I'm getting less than 6mpg driving like great-grandma, and when I gun it (which is rare) I have trouble getting speed. I couldn't keep pace with a Dodge 5.7 in a swb yesterday.....embarrassing.  Anyhow, since the issue began I have changed the plugs, wires, filter, cleaned carb, changed oil.  No change.  The truck is hard to start at times, then starts with a puff of black (sometimes grey) smoke, but most of the times I have no issue starting it.  Any suggestions on where to start?

[Irish_Alley]

how did you check for vacuum leaks?

welcome from maryland

[82silvy]

Nothing over a visual, looking for broken/missing/cracked lines. 

[Irish_Alley]

spray some carb cleaner around the intake and base of the carb see if the idle changes

[82silvy]

It did!  I also found two vacuum lines not connected to anything!  I'll have to track that down tomorrow.  I'm glad it's not my daily!  Thanks for your help, and I'll probably be bugging you again.

[82silvy]

Any ideas where to find a relatively easy to follow vacuum diagram?

[jg1977c20]

if the high idle is on then the secondary lockout lever is also engaged so the secondaries will never open - use some carb cleaner on the linkage and work it by hand even loosen the high idle screw by a 1/4 turn - personally i take that little lock out lever off - it was just there to keep the secondaries from opening while the choke is on ( pollution control) .

[Irish_Alley]

dont know about a vacuum diagram, but take pictures and we should be able to help.

[82silvy]

Any clue where the vacuum line coming out of the backside of the TCS solenoid goes? The single output on the right side of the picture.

[bd]

That is the TRC (Throttle Return Control) solenoid valve, not TCS (Transmission Controlled Spark).  The plastic vacuum tee connector on the right side of the valve (image) connects as follows:  straight port to manifold vacuum, normal (90°) port to TRC actuator on the carburetor.  The steel port adjacent to the electrical connections is a vent.

[82silvy]

Thank you!

[bd]

You're welcome.  Does the high idle issue go away if you leave the TRC actuator unplugged?

[82silvy]

No

[82silvy]

Apparently the connector was plugged in upside down after I replaced the TCS Solenoid.  Ooops..  Now I just have to figure out the bad gas mileage!