Thermac ?
#1
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Car: 1989 Iroc-Z Camaro
Engine: TBI,5.0
Transmission: Automatic 700R4
Axle/Gears: Eaton Posi,3.42,LPW Ultimate Cover
Thermac ?
I believe this is called a Thermac Switch.
Well I found out that the Thermac switch in the photo is staying in an open state allowing a major amount of air into the throttle body and IMO could be called a vacuum leak.
I put the stock assembly on and hooked up the Thermac switch hose like I always do and then set minimum idles speed.
.Is it really supposed to allow that much air into the throttle body at all times or is that a leak. I'm struggling with SMOG so really need to know.
Thanks
.
Well I found out that the Thermac switch in the photo is staying in an open state allowing a major amount of air into the throttle body and IMO could be called a vacuum leak.
I put the stock assembly on and hooked up the Thermac switch hose like I always do and then set minimum idles speed.
.Is it really supposed to allow that much air into the throttle body at all times or is that a leak. I'm struggling with SMOG so really need to know.
Thanks
.
#2
Re: Thermac ?
How hot is it?
Thermac supplies vacuum to the door motor on the air cleaner. Thermac is typically set at 100--120 degrees F.
When air in air cleaner housing is less than the thermac temp threshold, it will close or partially-close the air cleaner door. This brings heated air from the stove around the exhaust manifold into the air cleaner to prevent throttle icing and to help vaporize fuel.
When the air in the air cleaner is at or above the thermac threshold, the air door opens to allow cold air in for better performance.
So, yeah, it could be leaking air into the port on the throttle body when engine compartment or air cleaner temperature is high enough. Not a problem.
Thermac supplies vacuum to the door motor on the air cleaner. Thermac is typically set at 100--120 degrees F.
When air in air cleaner housing is less than the thermac temp threshold, it will close or partially-close the air cleaner door. This brings heated air from the stove around the exhaust manifold into the air cleaner to prevent throttle icing and to help vaporize fuel.
When the air in the air cleaner is at or above the thermac threshold, the air door opens to allow cold air in for better performance.
So, yeah, it could be leaking air into the port on the throttle body when engine compartment or air cleaner temperature is high enough. Not a problem.
#5
Re: Thermac ?
First Guess: Defective cat, defective EGR. Do you have an air pump, and does it work including the upstream/downstream valving?
Second Guess: You can deliberately screw-up the Thermac, but it won't accomplish anything useful.
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Car: 90 RS Wht/Blk Convert. Orig. owner
Engine: L03 & L31
Transmission: T5
Axle/Gears: 3.42
Re: Thermac ?
When NOx is too high your combustion temp is very high. To fix that you need to retard the timing. All you need to do is disconnect the spark advance wire, like when you set base timing. I think the single black wire has a pink stripe on it? The connector is located near the master cylinder or the heater box. Can't remember which side. I've moved my harness around so my car is not a good example anymore. Anyways, I always failed for NOx and then would just pull the plug and go for a retest. Passed every time.
#7
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Car: 1989 Iroc-Z Camaro
Engine: TBI,5.0
Transmission: Automatic 700R4
Axle/Gears: Eaton Posi,3.42,LPW Ultimate Cover
Re: Thermac ?
I appreciate that but unhooking the EST wire sets a engine light with my car and timing has to be stock 6* BTDC or it fails.
I'm just praying the new CAT does it. With the Thermac Switch creating such an unbridled amount of air flow its possible the ECM is compensating with a richer fuel mixture and causing trouble. If I could find a new Thermac Switch I would replace it.
The EGR valve and EGR Sensor are both brand new. So are the plugs , plug wires ,Coolant Temp. sensor, O2 sensor , Canister Purge valve and hoses, oil and filter are all brand new.
The smog pump is about 3 years old .
I really appreciate your help because if I cant find the problem the SMOG guys that CA trusts to find the problem start charging for the diagnoses at $260.00 for the first to hours and then $100.00 for every hour after that. One So called SMOG Repair shop said it has taken him up to 10 hours to find the problem. I all most laughed in his face telling him he would have to stop after 3 hours because that all I could afford.
I'm just so sick of all this.
Like I said thanks for all the help.
I'm just praying the new CAT does it. With the Thermac Switch creating such an unbridled amount of air flow its possible the ECM is compensating with a richer fuel mixture and causing trouble. If I could find a new Thermac Switch I would replace it.
The EGR valve and EGR Sensor are both brand new. So are the plugs , plug wires ,Coolant Temp. sensor, O2 sensor , Canister Purge valve and hoses, oil and filter are all brand new.
The smog pump is about 3 years old .
I really appreciate your help because if I cant find the problem the SMOG guys that CA trusts to find the problem start charging for the diagnoses at $260.00 for the first to hours and then $100.00 for every hour after that. One So called SMOG Repair shop said it has taken him up to 10 hours to find the problem. I all most laughed in his face telling him he would have to stop after 3 hours because that all I could afford.
I'm just so sick of all this.
Like I said thanks for all the help.
Last edited by Ron U.S.M.C.; 06-16-2015 at 10:19 PM.
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#8
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Re: Thermac ?
Ron. Try setting it to 4 degrees next time. That is within allowed variations.
It will help with the nox levels but I think you have other issues.
It will help with the nox levels but I think you have other issues.
#9
Re: Thermac ?
I'd expect the cat to have an effect on the high HC; especially if the air pump and diverter system works properly; and the rest of the feedback fuel system is within range. High HC is often be the result of misfire; but I don't see other signs of misfire in your test results. Let us hope that in this case, high HC is the result of a poisoned/overheated catalyst.
Compare the amount of air going through the Thermac to a disconected vacuum hose at the inlet to the Thermac. First Guess: The Thermac is not that big of a vacuum leak. If it's somehow defective in a way I don't understand...that's another story. Pull the vacuum supply hose off of the Thermac, and plug the vacuum hose. Does the high NOx go away???
Second Guess: If the thermac is a vacuum leak leaning the engine, the feedback fuel injection would richen the mixture, then close down the IAC to maintain idle speed. There'd be no difference in NOx, but the scan tool would indicate your fuel trim numbers are high, the ECM was in rich-command, and the IAC was more-closed than expected. As said, NOx is a product of high combustion temperature, and EGR was specifically designed to combat NOx. It makes sense to verify the EGR system, INCLUDING the exhaust passages in the cylinder head and intake manifold (they can plug with carbon so they don't pass exhaust gas) so even if the EGR valve works, there's no exhaust gas getting to the fuel/air mixture. Have you tested for vacuum at the valve at fast-idle? Have you seen the valve move in response to vacuum? If the EGR valve can be manually moved at idle, does idle quality suffer? (It should, EGR at idle makes for engine shake--which is why EGR is not activated at idle.)
The emissions test does not care how new the parts are. The emissions test passes or fails based on HOW THEY WORK. I get the sense that you have not tested these components.
A scan tool is your friend.
Second Guess: If the thermac is a vacuum leak leaning the engine, the feedback fuel injection would richen the mixture, then close down the IAC to maintain idle speed. There'd be no difference in NOx, but the scan tool would indicate your fuel trim numbers are high, the ECM was in rich-command, and the IAC was more-closed than expected. As said, NOx is a product of high combustion temperature, and EGR was specifically designed to combat NOx. It makes sense to verify the EGR system, INCLUDING the exhaust passages in the cylinder head and intake manifold (they can plug with carbon so they don't pass exhaust gas) so even if the EGR valve works, there's no exhaust gas getting to the fuel/air mixture. Have you tested for vacuum at the valve at fast-idle? Have you seen the valve move in response to vacuum? If the EGR valve can be manually moved at idle, does idle quality suffer? (It should, EGR at idle makes for engine shake--which is why EGR is not activated at idle.)
A scan tool is your friend.
Last edited by Schurkey; 06-17-2015 at 12:36 AM.
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Car: check
Engine: check
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Re: Thermac ?
Note that the higher base timing will increase HC and NOX.
RBob.
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Car: 75 Beast
Engine: 383 +EBL Flash
Transmission: 700R4
Axle/Gears: 4.11 with 33"
Re: Thermac ?
yaj15
Took a quick look at your test results. The exhaust is showing lean condition condition by the presence of excess O2 in the exhaust stream (1.1 to 1.3%) The high HC numbers indicate misfire or bad combustion in one or more cylinders. The O2 Sensor will detect extra O2 in the exhaust stream and additional fuel is added by ECM - making HC problem even worst.
As mentioned previously verify that base timing is set correctly - TBI cars are 0 deg - CAL spec allow +/-2 deg variance. Over advancing timing and non functional EGR will drive NOx numbers. High combustion temperatures due to advanced timing and carbon build up will result in high levels. A CAT replacement is last resort - make sure that engine is running at its best. AIR system is only active during cold and WOT so it is out of this picture during 15/25 mph test.
Do not worry about thermac - it is only used when inlet airstream is cold to activate diverter flapper. During the test air is almost always hot. Just make sure that all vacuum tubes are connected to satisfy visual inspection rules.
Good luck with it.
//RF
Took a quick look at your test results. The exhaust is showing lean condition condition by the presence of excess O2 in the exhaust stream (1.1 to 1.3%) The high HC numbers indicate misfire or bad combustion in one or more cylinders. The O2 Sensor will detect extra O2 in the exhaust stream and additional fuel is added by ECM - making HC problem even worst.
As mentioned previously verify that base timing is set correctly - TBI cars are 0 deg - CAL spec allow +/-2 deg variance. Over advancing timing and non functional EGR will drive NOx numbers. High combustion temperatures due to advanced timing and carbon build up will result in high levels. A CAT replacement is last resort - make sure that engine is running at its best. AIR system is only active during cold and WOT so it is out of this picture during 15/25 mph test.
Do not worry about thermac - it is only used when inlet airstream is cold to activate diverter flapper. During the test air is almost always hot. Just make sure that all vacuum tubes are connected to satisfy visual inspection rules.
Good luck with it.
//RF
#14
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Car: 1989 Iroc-Z Camaro
Engine: TBI,5.0
Transmission: Automatic 700R4
Axle/Gears: Eaton Posi,3.42,LPW Ultimate Cover
Re: Thermac ?
The man running the test is the same guy for the last 8 years. He is adamant about the 6* and has checked it at two different sources. I was still in doubt but finally took a look carefully at my Chiltons and sure enough = 6* at 700 rpm. I preform the IACV reset then set minimum idle speed with EST wire disconnected to 700 rpm.
Timing at 6* and the stock components installed including the Thermac switch.
Tomorrow I will perform a few tests and get back to you guys. Thanks tremendously for all the help.
But the way where can I buy a different Thermac switch. Cant seem to find one.
Timing at 6* and the stock components installed including the Thermac switch.
Tomorrow I will perform a few tests and get back to you guys. Thanks tremendously for all the help.
But the way where can I buy a different Thermac switch. Cant seem to find one.
Last edited by Ron U.S.M.C.; 06-25-2015 at 09:37 PM.
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Re: Thermac ?
Ron
Thermac switches have been discontinued and only a few generic later models are still available. Expect to pay top dollar!! Standard motor parts SMP has a universal replacement: STANDARD MOTOR PRODUCTS Part # ATS3 {#213112, 213114, 6484244, 6484587, E3241, E32414, E3243} - Check Rock Auto
Your friend and Chilton manual are wrong - if you have TBI (throttle body injection) car base timing per factory manual is 0 deg with EST plug open. The 6 deg is for TPI (tuned port injection) equipped engines.
Photo is from GM FSM
//RF
Thermac switches have been discontinued and only a few generic later models are still available. Expect to pay top dollar!! Standard motor parts SMP has a universal replacement: STANDARD MOTOR PRODUCTS Part # ATS3 {#213112, 213114, 6484244, 6484587, E3241, E32414, E3243} - Check Rock Auto
Your friend and Chilton manual are wrong - if you have TBI (throttle body injection) car base timing per factory manual is 0 deg with EST plug open. The 6 deg is for TPI (tuned port injection) equipped engines.
Photo is from GM FSM
//RF
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Car: 1989 Iroc-Z Camaro
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Re: Thermac ?
Thank you
I went on line and looked at the "89 5.0 E AUTOMATIC & MANUAL TRANS EMISSIONS DECAL (DCA)"
for my car. Here's what I found everywhere. I made a copy of it and have a shop or two to visit tomorrow. I'm just trying to gather some physical proof and then order the decal for the one missing on my car.
My vin is E so this is a match.
I went on line and looked at the "89 5.0 E AUTOMATIC & MANUAL TRANS EMISSIONS DECAL (DCA)"
for my car. Here's what I found everywhere. I made a copy of it and have a shop or two to visit tomorrow. I'm just trying to gather some physical proof and then order the decal for the one missing on my car.
My vin is E so this is a match.
Last edited by Ron U.S.M.C.; 06-26-2015 at 02:00 AM.
#17
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Car: 1989 Iroc-Z Camaro
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Transmission: Automatic 700R4
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Re: Thermac ?
Turns out the photo above is correct for a Federal vehicle.
The new SMOG shop I went to today also has the car put at 6* BTDC.
He said to go to GM Dealer and see if I could get the sticker there . They said is no longer produced.
I'm taking a trip to Pick n Pull tomorrow.
I also talked to the SMOG technician about the Thermac switch and he said it is fine and working the way it should.
I know I'm making a big deal out of this but for me it is.
The new SMOG shop I went to today also has the car put at 6* BTDC.
He said to go to GM Dealer and see if I could get the sticker there . They said is no longer produced.
I'm taking a trip to Pick n Pull tomorrow.
I also talked to the SMOG technician about the Thermac switch and he said it is fine and working the way it should.
I know I'm making a big deal out of this but for me it is.
Last edited by Ron U.S.M.C.; 06-26-2015 at 11:40 PM.
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Car: 1989 Iroc-Z Camaro
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Re: Thermac ?
Up date
I finally found a CA legal emissions label for my exact car at Classic Industries . It was not in the online catalog. Its part # DT719 = http://www.classicindustries.com/pro...rts/dt719.html
I'm still going to pick n pull because the deadline is the July 5th.
Now I need a photo of its exact location for a car with A/C.
I finally found a CA legal emissions label for my exact car at Classic Industries . It was not in the online catalog. Its part # DT719 = http://www.classicindustries.com/pro...rts/dt719.html
I'm still going to pick n pull because the deadline is the July 5th.
Now I need a photo of its exact location for a car with A/C.
#20
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Car: 1989 Iroc-Z Camaro
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Re: Thermac ?
I also have the Emissions sticker to put on the car that says 0* is the stock setting.
He will honor it starting 2 years from now when I do this again.
Thanks everyone for there help.
He will honor it starting 2 years from now when I do this again.
Thanks everyone for there help.
Last edited by Ron U.S.M.C.; 07-03-2015 at 11:45 PM.
#21
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Re: Thermac ?
I believe this is called a Thermac Switch.
Well I found out that the Thermac switch in the photo is staying in an open state allowing a major amount of air into the throttle body and IMO could be called a vacuum leak.
I put the stock assembly on and hooked up the Thermac switch hose like I always do and then set minimum idles speed.
.Is it really supposed to allow that much air into the throttle body at all times or is that a leak. I'm struggling with SMOG so really need to know.
Thanks
.
Well I found out that the Thermac switch in the photo is staying in an open state allowing a major amount of air into the throttle body and IMO could be called a vacuum leak.
I put the stock assembly on and hooked up the Thermac switch hose like I always do and then set minimum idles speed.
.Is it really supposed to allow that much air into the throttle body at all times or is that a leak. I'm struggling with SMOG so really need to know.
Thanks
.
Has anyone seen this before? I take it that the pin hole is a result of the metal rusting and it was not intended to be a pressure relief? In other words I have a vaccum leak no matter the inlet temperature.
Thoughts?
Thanks for looking.
-Chris
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