Author Topic: Throttle Control & CA Emissions  (Read 10285 times)

Offline KoolK10

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Throttle Control & CA Emissions
« on: March 24, 2014, 05:43:29 PM »
First off...many thanks to all of you guys here in this forum. I've been going through threads for a couple months and have already picked up a ton of useful info. Finally registered today because I have a couple questions that I couldn't find the answer to.

Particulars:
1977 K10
Camper Special
6200 GVWR
5.7L 350
No A/C

I've had quite a go at trying to get this thing smogged here in CA and have had a number of different opinions on the subject. At the end of the day, I'm just looking to get this sucker passed so I can start using it. Doin' no good just sittin' around with me tinkering on it if I can't get it out on the road, yknow?

I've had someone helping me out who used to be a smog tech but I'm not certain that everything is up to snuff. Thought a few experts could chime in and help me out...??

I failed my first smog test a couple months ago. She breathed fine, but didn't pass visual and timing. The tech there was of no help whatsoever. I took it to a new place last week and he didn't test it because again, it wouldn't pass visual. Mainly just the TLA. The guy gave me the schematic that would work best for my truck, so, I've been going off of this printout.   CA Heavy Duty Emissions -- Less A/C (Pic 1)

I believe I've got everything hooked up as per the schematic except for the (TLA - "Throttle Lever Actuator". Is this contraption also known as a "dashpot"?  The guy helping me out said that's what it is, and that I don't need it as it's just to run the A/C, but like I said, I'm kind of weary about that.

See Pic 2
A). Is this the Throttle Lever Acutator?
B). If so, what is the contraption that it's hooked in to? (With the 2 prongs)

Right now the 2 prong contraption is T'd off in the back with one vac line going to the carb, while the other goes into (what I"m assuming) is the Throttle Lever Actuator.

C). Where does the connection from the 2 prongs go to?  I can't find it for the life of me!  Rrrggghh. Also, there appears to be another vacuum port underneath the 2 prongs. Does this need to be hooked up too?  Any leads on where I can pick up a connector...and what it's called.

I have more pics if that helps anyone here. Just let me know and I'll post 'em up. Any help though with this is MUCH appreciated.  I've turned a few wrenches in my life, but this CA Emissions is a bear!


Offline bd

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Re: Throttle Control & CA Emissions
« Reply #1 on: March 24, 2014, 08:03:22 PM »
Welcome to the site!

Picture 2 shows the TLA and its vacuum control valve.  Here's what you need to know.  The TRC (Throttle Return Control) diagram the smog tech provided, Picture 1, is one year "older technology" than you have on your truck - see the 1976 Service Manual, page 6T-7 (Pg 169) with regard to the diagram that you were given.  The older TRC system operates by manifold pressure.

Your truck has a newer version of that same system - see the 1979 Service Manual, page 6E-26 (Pg 815) for reference.  The newer TRC system operates by monitoring engine RPM.  The third 'vacuum port' on the solenoid, located below the electrical connection, is a "vent" that is left open to atmosphere.

Essentially, the TRC system is an anti-backfire device that reduces unburned HC entering the exhaust during deceleration and is a mandatory emission device in California.

Additional useful information maybe found in the Technical Pages of the Forum.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline KoolK10

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Re: Throttle Control & CA Emissions
« Reply #2 on: March 24, 2014, 08:35:29 PM »
Very helpful stuff...thank you!

So...according to the '79 descriptions / diagrams, it appears that I just need to hook up the electric connection on the control valve to an electronic speed sensor. (Which monitors engine speed at the distributor). Sounds easy enough.

If I'm on the right track...how can I go about finding that connection. I've googled around and have come up short. I know parts can go by different names though maybe that's the case...?  Any parts houses that anyone here has had success w/ parts like this?  Or am I making another trip to the junkyard maybe?

Thanks again.

Offline bd

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Re: Throttle Control & CA Emissions
« Reply #3 on: March 24, 2014, 08:54:13 PM »
I believe a Series 56 connector will work for you, or something similar.  Local parts houses should have these in their electrical sections.
« Last Edit: March 24, 2014, 08:57:18 PM by bd »
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline KoolK10

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Re: Throttle Control & CA Emissions
« Reply #4 on: March 24, 2014, 11:20:32 PM »
Ok...I might've gotten ahead of myself. 

The Electronic Speed Sensor...what does that puppy look like? 

Thanks for the link to the Series 56 connector....just wondering where it leads to once connected to the Control Valve?   Pic on Page 816 of the '79 Manual just shows the "Valve Assembly" with what looks to be one of those Series 56 connectors...but doesn't detail where it's going.  I understand the diagram above it on page 815, but just need to understand what I should be looking for. 

The manual references that it's a switching device that's mounted separately. Just went out with a flashlight and crawled all over.  Don't see anything that matches that description. What / Where should I be looking?  If I don't indeed have one, are these readily available at parts houses too?  Couldn't find any matches in my initial search. A GM part # would help??

Please excuse my ignorance on this...I feel so dumb. This TRC is just new to me and I'm trying to get my head wrapped around it. Appreciate your insight and patience too.

~Brandon

Offline bd

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Re: Throttle Control & CA Emissions
« Reply #5 on: March 25, 2014, 03:29:19 PM »
Go into your local Chevy/GMC dealer.  If they have books that old they can provide a part number.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline bd

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Re: Throttle Control & CA Emissions
« Reply #6 on: March 28, 2014, 10:08:54 PM »
KoolK10, did you resolve this?  Our 1977 Service Manual is recently available and matches the diagram supplied by the smog tech (see Figure 6E-10 on page 6E-7 (Pg 651)).

The tach-controlled TRC system on your truck doesn't appear original to your '77 K10.  IIRC, the 'older' style vacuum control valve illustrated in the emission diagram became obsolete from GM in the early to mid-90's.  It caused quite a stir at the time as more trucks began needing them.  Yours may have been updated to the newer design in response to a scarcity of service parts(?).  Unfortunately, some emission components from that era are difficult to source, if even available.  You may need to rely on a salvage yard or NOS from a dealer who hasn't purged it yet from inventory (a long shot).  If you can procure part numbers, a Chevy/GMC dealer can run them on their national parts locator network to search dealer inventory nationwide. 

Good luck with this and let us know the outcome.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline KoolK10

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Re: Throttle Control & CA Emissions
« Reply #7 on: March 29, 2014, 07:53:20 PM »
bd - Thanks for the link to that manual. That's gonna help me out a ton!

So I took your advice and went down to my local dealer with those parts in hand. (TLA and control valve). Super helpful guys down there and they were trying to source parts (or even part #'s) for those units, as well as trying to find a schematic that shows where that control valve was supposed to hook in to. Came up empty. Not even a part #. Old school Parts Manager walks in and just starts laughing. Takes one look at those parts and says "You'll never find 'em". Your memory does serve you correct -bd...PM goes on to say that they stopped making those parts about over 15 years ago and to try to source them would be next to impossible. Said any knowledgeable smog tech and/or referee would know that and not make it a requirement to pass visual. 

Spoke w/ another smog place here in town who seem to know their stuff...we discussed the situation, etc. Gonna take the ol' K10 in first thing Monday morning and try to get 'er passed.

Wish me luck.

Thanks for following up. I'll be sure to keep you posted.

Again, many thanks,

~B

Offline KoolK10

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Re: Throttle Control & CA Emissions
« Reply #8 on: April 15, 2014, 07:06:57 PM »
Ok...it has been quite the process, but I FINALLY got the beast smogged today. I'm thrilled.

The shop that I took it to was super helpful, so that was a big plus. The BAR label on the door jamb was extremely hard to read, but after cleaning it up a bit, we found that it was from 1975 (not 1977 which is how the truck is registered). They were hesitant to run it based on '75 specs as the owner of the shop questioned it's validity. Plus, it had too much smog equipment for them to run it as a 75 anyways. (Smog pump, etc) Go figure. CA won't let you smog it if it has TOO MUCH smog equipment. Gotta love the irony there. Anyways, they suggested I head down to the referee and get it dialed in.

Appt with the referee was pretty smooth. Old guy had a '76 himself and was a wealth of info when it came to emissions on these trucks. He verified that it was in fact a '77 and gave me that same schematic that I was working on already. Tested it for free, and it breathed fine, (both emissions and evap), but did not pass visual for lack of the control valve. The part that I originally had (with the 2 prong electrical) he said was trash...didn't even belong on the vehicle.  That was a relief. I was lucky enough to find the part I needed on ebay for $35. (Conrol Valve for Throttle Return Control System - http://www.ebay.com/itm/191129647766). Hooked it up and a couple other BS things that the ref added on my compliance checklist (pre-heater tube had to be connected to my exhaust manifold, had to take out a delay valve, and a couple other no-cost easy fixes).

Returned to the shop this morning and it passed with flying colors.

Celebrated by taking my son out to the lake today. What a blast.

Lookin' forward to gettin' her out on the road more now and spending my time doing some other fixes that I WANT to do vs HAVE to do to just to pass smog here in CA. What a joke.

Just wanted to give you all an update. Thanks again bd.

~B


Offline bake74

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Re: Throttle Control & CA Emissions
« Reply #9 on: April 16, 2014, 12:09:51 AM »
     Glad to hear you got it smogged.  Though in CA. 75 and older does not need to be smogged.  (that is why I only have 73 - 75, that is registered anyways).
     Go out and enjoy it now.
#1: The easiest and most obvious solution to any problem is 99% of the time correct.
#2: There is no such thing as impossible, it just takes longer.
  74 k10, 77k10    Tom

Offline bd

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Re: Throttle Control & CA Emissions
« Reply #10 on: April 16, 2014, 12:32:50 AM »
Thanks for the detailed update.  Good job on locating that valve!  And, like Bake74, I'm pleased to learn that California's bureaucratic aggravation is behind you.   :D


So.... did you drive your truck to the lake?   ???
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline KoolK10

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Re: Throttle Control & CA Emissions
« Reply #11 on: April 16, 2014, 10:10:33 AM »
Oh yeah...took the truck to the lake for a day of fishing and jet-skiing. I think my son (he's 10) was just as excited as I was to get it out on the open road.  8)

Now on to the to-do list:

Investigate / repair why it's still backfiring through the exhaust
New drive gear for the T-case so my speedo works
Repair clutch linkage (it's too loose right now)
Carb rebuild kit
3 point seat belts
New tires
Dash cover

Offline mrbetelman

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Re: Throttle Control & CA Emissions
« Reply #12 on: August 16, 2020, 07:41:12 PM »
I just wanted to let anyone of you folks that are still on here that this post is still very helpful in 202. Thanks again...