THERMAC valve not working. bad starts

[2500sierra81]

so my THERMAC diverter valve isnt working. its supposed to block off oustide air during a cold start. thing is i can't find any online stores that sell new motors for the valve. anyone had this problem or know where to get a new one? i'd like to have it fixed because i have to spend a good ten minutes holding the gas down to warm the engine up in the morning.

also when i start the engine, it starts to lope. like its uneven firing. thing is it only does it on a cold start. is this a choke problem or is this also related to the THERMAC thing? with this hard start and loping thing it thorw out lots of black smoke. any other time it runs fine, with out smoke and even running

 

[bucket]

The thermac valve on the air cleaner? It doesn't really do much and is likely not causing any of your issues (and all of them I've seen are heat actuated, not electric). Mine starts fine in the dead of winter and it has an open element air cleaner on it.

 

[2500sierra81]

ok. so what could be causing the problems i described? is it my carb? or the timing? i've heard people mention both as problems, but the thing is they run fine once the engine is warm...

 

[smurph20]

Is the choke even working? It may be hooked up but is it moving the linkage when its needed to warm the truck up?

 

[crazy4offroad]

Sounds to me like the choke is out of adjustment.
AHH ya beat me Brad lol

 

[HotRodPC]

Sounds to me the choke is adjusted to tight, and coming on to quick and staying on. Also could be that the choke is OK, but the choke pull off is not operating. But, rule out the ThermoVac. Those rarely worked for long anyway. All they did was block off the cold air at the air cleaner so that warmer air off the heat stove from the exhaust manifold would get up the carb first. That isn't going to cause your issues and if it doesn't work at all, I woudln't sweat it.

 

[Jims86]

Yup, what they said^^^^
Where in Cali are you?

 

[2500sierra81]

Yup, what they said^^^^
Where in Cali are you?

san anselmo
marin county

 

[Jims86]

Call Gm auto recycling in Rancho Cordova at 800-541-8169 for the valve. You may have to buy the whole air cleaner, but it should not cost a lot, they will ship to you.
I wish I was closer to you, I could help you get that carb setup...I used to live across the SR Bridge from you.
Out by Modesto now.

 

[HotRodPC]

Does Cali still require for the Thermostatic Air Cleaner to operate properly for passing emmisions??? If not, I'd blow it off. IF they do, then put it on ONLY to smog test, then put an aftermarket air cleaner on after the test and keep the Thermostatic one in the garage in a nice dry place with a shot of WD-40 or Liquid Wrench at the pintle of the ThermVac.

 

[Jims86]

Does Cali still require for the Thermostatic Air Cleaner to operate properly for passing emmisions???

Yup.
I wish they would make vehicles 20 years or older exempt....at least from the visual.

 

[HotRodPC]

Yup.
I wish they would make vehicles 20 years or older exempt....at least from the visual.

That sucks for what little it does.

 

[skysurfer]

Does Cali still require for the Thermostatic Air Cleaner to operate properly for passing emmisions???

Yup.

Hey Jim, have you ever seen the test tech actually check the operation of the TAC? Around here they just do a visual to see if the heat riser tube is intact then move on with the rest of the test. None of them even care that I've added a second snorkel, which effectively renders the TAC inop.

 

[HotRodPC]

Hey Jim, have you ever seen the test tech actually check the operation of the TAC? Around here they just do a visual to see if the heat riser tube is intact then move on with the rest of the test. None of them even care that I've added a second snorkel, which effectively renders the TAC inop.

Yup, you're right sky. Pretty much it's a visual on the stove pipe. And we did fail a car if it came in with the lid flipped on the air cleaner. Acually we went out to the lobby and gave them a tongue lashing, and told them to come into the shop a flip it back, that if we did it, we'd first have to fail it, then charge a fix fee, then a retest fee. Then told them, before coming in for a test, flip it, and if he wanted to flip it back after I signed his test sheet, I didn't give a rats ass. I was easy on that frivolous chicken **** bs but I never once, and was a hard ass on tailpipe emmisions. That is what counts anyway.

 

[Jims86]

Hey Jim, have you ever seen the test tech actually check the operation of the TAC? Around here they just do a visual to see if the heat riser tube is intact then move on with the rest of the test. None of them even care that I've added a second snorkel, which effectively renders the TAC inop.

Yes, when I still had my carb on the burb, they hooked up a vacuum pump to operate it...that was before the TBI air cleaners with the bi metal spring.