Throttle body to sensor(?) in air cleaner vacuum line question

[MattfromMaine]

Quick question for those with much more knowledge than me....

We're talking about my '72 Newport with the 400 and original 2210 carb. So, I've done a bunch over the last few months and have most things sorted out to make this a fun summer car and it has gone well. It has been running like a top so I took it to Mount Desert Island here in Maine last Sunday (about 200 miles round trip) and it drove beautifully. Parked it and fired it up two days later, no problems initially but got to the first stop sign and the second I stopped, I noticed that it was idling really low..... on the brink of stalling or like it has a fire-breathing, high HP cam in it. I put it into neutral, same thing. Put it into park, same thing. Once I got going, it was smooth as can be.

Well, I started reading threads on here and found a few pieces on info to help me diagnose (smelling oil for fuel, wrong order from the distributer) but all of that checked out. I thought maybe due to the long drive, the idle screws may have loosened b/c honestly, I thought it just needed to be idled up. Interestingly enough, with this problem, fast idle is now what a warmed up idle should be and my curb idle is super low as I previously described.

So, I pulled off the air cleaner and checked the three vacuum hoses that come off of it and all was well. I looked things over, found the idle screws and fired the car up. I noticed it seemed to be running better. I let it warm up and moved it around in my driveway without the air cleaner to get it to click down to the super low idle I'd been experiencing and I couldn't get it to do it. I still idled it up a half turn on both the curb idle and fast idle and it sounded great. I decided to throw the air cleaner back on and the second I put the vacuum hose on the back of the carb that goes from the throttle body to the sensor looking thing in the air cleaner (technical name for it, I'm sure) it immediately bogged down. Vacuum line is clear and in good condition.

I've pinpointed the location of the problem but in researching what it is that is in the air cleaner and what I need to do to it, I've come up empty. I'm guessing there are more than a few on here that know exactly what is going on. I wanted to just leave it undone and drive but thought I check with everyone here first. Thank you in advance for any info you can provide!

 

[Davea Lux]

First off, that is not a throttle position sensor, no such thing in '72. That is the sensor for the preheat tube. Starting in about '70, some mopar vehicles had a vacuum motor attached to the air horn on the air cleaner that operated a small flapper valve that diverted incoming air from the air horn to the heat stove located on the driver side exhaust manifold. These sensors were famous for blowing out if the engine farted back thru the carb. Then they would leak. Part has been obsolete for many years. If this is a summertime cruiser, you can block off the port and not hurt anything. Leaner fuel settings with the start of the emission era could cause carb icing in humid, cold conditions and running warm air off the exhaust manifold helped control this. The warm air also improved performance until the engine warmed up. Trying to find a replacement sensor is going to be a crap shoot since most people just disconnected the sensor if it failed. You might try Murray Park or AMS obsolete to see if they have it.

Dave

 

[MattfromMaine]

First off, that is not a throttle position sensor, no such thing in '72. That is the sensor for the preheat tube. Starting in about '70, some mopar vehicles had a vacuum motor attached to the air horn on the air cleaner that operated a small flapper valve that diverted incoming air from the air horn to the heat stove located on the driver side exhaust manifold. These sensors were famous for blowing out if the engine farted back thru the carb. Then they would leak. Part has been obsolete for many years. If this is a summertime cruiser, you can block off the port and not hurt anything. Leaner fuel settings with the start of the emission era could cause carb icing in humid, cold conditions and running warm air off the exhaust manifold helped control this. The warm air also improved performance until the engine warmed up. Trying to find a replacement sensor is going to be a crap shoot since most people just disconnected the sensor if it failed. You might try Murray Park or AMS obsolete to see if they have it.

Dave

Awesome!!! Thanks so much for the info. VERY hard to find info on this particular part. No clue where I would get such detailed and accurate info if this site didn't exist. MUCH appreciated!

 

[saforwardlook]

Since you have a model 2210 Holley 2 bbl carburetor, you should be aware that they are very prone for the air horns on top of the carburetors to warp. When they do begin to do that, the symptoms you are experiencing are symptomatic of it starting to warp enough to cause low idle speeds, rough running and stumbles and pass outs on acceleration. Connecting the rubber hose to the air cleaner temp sensor might have been just a coincidence.

Just something to keep in mind as you continue to drive the vehicle. If it becomes more routine, you will need to have the carburetor rebuilt by a competent shop familiar with this issue. One such company is Autoline Carburetors of Winnipeg, Manitoba, Canada...............they press the top of the carburetor down with significant force and then have to plane it flat to correct the issue. Overtightening the air horn wing nut leads to this condition as a prime cause of the warpage. The design was flawed because the rod to which the air cleaner hold down wing nut attaches is itself attached to the airhorn of the carburetor rather than attaching to the base plate of the carburetor. A big mistake.

https://autoline.ca/

 

[CBODY67]

As the car was running well before the idle suddenly lowered, then what you've found is probably NOT the issue.

That temp sensor gets manifold vacuum, which it then modulates to aim for 100 degrees F inside the air cleaner, thereby allowing a more specific main jet metering environment to reduce vehicle emissions, idle and otherwise. The actuator in the snorkel should get its air from the heat stove on the exhaust manifold, IF the shroud on the exhaust manifold is still present AND connected by the flex tube to the bottom of the snorkel.

If you're concerned about the sensor/motor operating, just put a cap on the vacuum port that supplies vacuum to the sensor.

As noted, the Holley 2210 did have an issue with the air horn warping. Chrysler had a "fix kit" to address/fix that issue, but finding one is pretty rare, although I have seen some on eBay every so often. The prior Stromberg WWC 2bbls had similar issues, too. Key thing, do NOT tighten the air cleaner nut more than just to make sure everything's seated. NO POINTS for more than that! Due to the way the Carter BBDs had their air cleaner stud attached, they had no such issues.

How to tell if the air horn has warped? Two ways. MPG will be no more than about 10mpg as the signal to the power valve is gone, which means the carb is on full power mixture all the time. As the engine is "on choke" and fast idle, the semi-closed choke plate can cause raw fuel to be sucked out of the float bowl and into the throttle bores, resulting in very rough running AND a very rich mixture which will go away as soon as the choke thermostat lets the choke plate open more.

Smell the motor oil, checking for a fuel-type smell, indicating a rich mixture.

With the mainfold vacuum port on the rear of the carb open, it fhe carb was running too rich, the idle speed would have increased and still be a bit rough.

With the engine idling rough, is it hard or easy to re-start? Extended crank time, more than normal?

Check the ignition timing with a timing light. IF you have to move the distributor about "1 notch", or enough that it puts the wires "1 notch off" from what they should be, effectively, in order to get the timing to be correct again, then you probably have a timing chain that's jumped a tooth. One afternoon I was at the local Chrysler dealership, a highway patrol vehicle came in acting like that. The service manager did a timing check and then advanced the distributor position that much and it idle like it should. The timing chain was his diagnosis. Being an old-line Chrysler tech and such, working on Dodge Bros. cars in his youth, I trusted his judgment.

To me, ANY engine that uses a plastic/steel timing sprocket, with more than about 80K on it, is prime territory to need the timing chain/sprocket replaced with a new one. Either a quality OEM-level replacement of a double-roller timing set (as Mopar Perf used to sell, or similar).

When the timing chain flaked on our '72 Newport 400, it was hard to start and would usually backfire until it did. Getting almost to that point where it'd run, but not quite there, as I was cranking on it.

Please keep us posted,
CBODY67

 

[MattfromMaine]

As the car was running well before the idle suddenly lowered, then what you've found is probably NOT the issue.

That temp sensor gets manifold vacuum, which it then modulates to aim for 100 degrees F inside the air cleaner, thereby allowing a more specific main jet metering environment to reduce vehicle emissions, idle and otherwise. The actuator in the snorkel should get its air from the heat stove on the exhaust manifold, IF the shroud on the exhaust manifold is still present AND connected by the flex tube to the bottom of the snorkel.

If you're concerned about the sensor/motor operating, just put a cap on the vacuum port that supplies vacuum to the sensor.

As noted, the Holley 2210 did have an issue with the air horn warping. Chrysler had a "fix kit" to address/fix that issue, but finding one is pretty rare, although I have seen some on eBay every so often. The prior Stromberg WWC 2bbls had similar issues, too. Key thing, do NOT tighten the air cleaner nut more than just to make sure everything's seated. NO POINTS for more than that! Due to the way the Carter BBDs had their air cleaner stud attached, they had no such issues.

How to tell if the air horn has warped? Two ways. MPG will be no more than about 10mpg as the signal to the power valve is gone, which means the carb is on full power mixture all the time. As the engine is "on choke" and fast idle, the semi-closed choke plate can cause raw fuel to be sucked out of the float bowl and into the throttle bores, resulting in very rough running AND a very rich mixture which will go away as soon as the choke thermostat lets the choke plate open more.

Smell the motor oil, checking for a fuel-type smell, indicating a rich mixture.

With the mainfold vacuum port on the rear of the carb open, it fhe carb was running too rich, the idle speed would have increased and still be a bit rough.

With the engine idling rough, is it hard or easy to re-start? Extended crank time, more than normal?

Check the ignition timing with a timing light. IF you have to move the distributor about "1 notch", or enough that it puts the wires "1 notch off" from what they should be, effectively, in order to get the timing to be correct again, then you probably have a timing chain that's jumped a tooth. One afternoon I was at the local Chrysler dealership, a highway patrol vehicle came in acting like that. The service manager did a timing check and then advanced the distributor position that much and it idle like it should. The timing chain was his diagnosis. Being an old-line Chrysler tech and such, working on Dodge Bros. cars in his youth, I trusted his judgment.

To me, ANY engine that uses a plastic/steel timing sprocket, with more than about 80K on it, is prime territory to need the timing chain/sprocket replaced with a new one. Either a quality OEM-level replacement of a double-roller timing set (as Mopar Perf used to sell, or similar).

When the timing chain flaked on our '72 Newport 400, it was hard to start and would usually backfire until it did. Getting almost to that point where it'd run, but not quite there, as I was cranking on it.

Please keep us posted,
CBODY67

Thank you for the thorough reply. Interesting info... First, I've been wondering what to do with the vacuum port, given the engine has the issue when it's capped. My thought was to completely remove the temp sensor so that when I connect the vacuum line to the air cleaner, it's just open pulling filtered air. The shroud on the exhaust manifold is there but the flex tube to the bottom of the snorkel is long gone.

Regarding the air horn being warped, not completely sure what I'm getting for MPG but it hasn't seemed outrageous. I'm going to calculate to get a number. It has however, started rough at times and snapped out of it after about 15-20 seconds after starting it, gradually increasing to fast idle. Not smelling a fuel smell in the oil.

When running rough or smooth, it has never been hard to start. Well, once last month but it turned out that the alternator was dying. Other than that, it's always fired up immediately. Right before the trip, I used fuel treatment and thought that that might have played a part (although I'm not sure how it would have effected the specific vacuum port we're talking about). The product I used was K100 (K100-G+ 8 oz. – 3 Pack | Fuel Treatment and Gas Additive | Ethanol Treatment | Kinetic Fuel Technology Inc) and I've put ethanol-free gas in since I've bought it.

Thanks in advance for any other insight you may have!

 

[Davea Lux]

Thank you for the thorough reply. Interesting info... First, I've been wondering what to do with the vacuum port, given the engine has the issue when it's capped. My thought was to completely remove the temp sensor so that when I connect the vacuum line to the air cleaner, it's just open pulling filtered air. The shroud on the exhaust manifold is there but the flex tube to the bottom of the snorkel is long gone.

Regarding the air horn being warped, not completely sure what I'm getting for MPG but it hasn't seemed outrageous. I'm going to calculate to get a number. It has however, started rough at times and snapped out of it after about 15-20 seconds after starting it, gradually increasing to fast idle. Not smelling a fuel smell in the oil.

When running rough or smooth, it has never been hard to start. Well, once last month but it turned out that the alternator was dying. Other than that, it's always fired up immediately. Right before the trip, I used fuel treatment and thought that that might have played a part (although I'm not sure how it would have effected the specific vacuum port we're talking about). The product I used was K100 (K100-G+ 8 oz. – 3 Pack | Fuel Treatment and Gas Additive | Ethanol Treatment | Kinetic Fuel Technology Inc) and I've put ethanol-free gas in since I've bought it.

Thanks in advance for any other insight you may have!

One of the problems with fuel treatments is that they sometimes break lose a bunch of accumulated crud in the fuel system. Pull the air cleaner and start the engine. Then turn it off and look down the carb throat with a flashlight, do you see gas dripping anyplace in the throttle bores? If so you may have debris under the needle and seat keeping it from properly closing. A a car this age is is also not uncommon to have a carb float that is fuel logged, that will also cause the carb to flood over. If you have a leak at the sensor, you are injecting more air into the fuel mixture with the line connected, that suggest the carb is running too rich. Not a good idea to leave any vacuum port unhooked as dirt can enter the engine that way.

Dave

 

[CBODY67]

ANOTHER thing with "fuel treatments" is that many contain ALCOHOL, especially if their dialogue might mention "water/moisture removal". With E10 being what it is, adding more alcohol into the mix can make things worse, in that respect. The possisble "good thing" is that with the larger fuel tank, whatever was added will have less affect than if it was a newer vehicle with a 16 gallon tank.

How long has the fuel been in the tank? How much? How many miles after the last fill-up/addition before things started getting flaky? Just curious.

I fully understand your concerns that some system on the car is having issues, but it could well be the fuel itself. One time, I filled up from a larger-private brand station I'd been getting fuel from in other parts of the area. After I drove it a while, coming home, I noticed that it didn't want to idle as usual, but needed additional throttle to stay running at red lights and such. The exhaust had a more hollow sound, too. Didn't really start "hard", but took a little bit longer, with a little more throttle needed. No big deal, but it started with that particular load of new fuel. So I "drove it out", refilled with better fuel, and all was well. Perhaps this might be similar to what you might need to do?

With no vacuum going to the sensor, the flap in the snorkel remains open, which is what you mention desiring. Also remove the vac line going to the sensor, for cosmetics. Just compress the retention clip to make that happen.

Take care,
CBODY67

 

[MattfromMaine]

One of the problems with fuel treatments is that they sometimes break lose a bunch of accumulated crud in the fuel system. Pull the air cleaner and start the engine. Then turn it off and look down the carb throat with a flashlight, do you see gas dripping anyplace in the throttle bores? If so you may have debris under the needle and seat keeping it from properly closing. A a car this age is is also not uncommon to have a carb float that is fuel logged, that will also cause the carb to flood over. If you have a leak at the sensor, you are injecting more air into the fuel mixture with the line connected, that suggest the carb is running too rich. Not a good idea to leave any vacuum port unhooked as dirt can enter the engine that way.

Dave

This makes a whole lot of sense, given the timeline of events. I'll take a look down the carb tomorrow and see what it's looking like and report back what I see. Thanks again for your help!

 

[MattfromMaine]

ANOTHER thing with "fuel treatments" is that many contain ALCOHOL, especially if their dialogue might mention "water/moisture removal". With E10 being what it is, adding more alcohol into the mix can make things worse, in that respect. The possisble "good thing" is that with the larger fuel tank, whatever was added will have less affect than if it was a newer vehicle with a 16 gallon tank.

How long has the fuel been in the tank? How much? How many miles after the last fill-up/addition before things started getting flaky? Just curious.

I fully understand your concerns that some system on the car is having issues, but it could well be the fuel itself. One time, I filled up from a larger-private brand station I'd been getting fuel from in other parts of the area. After I drove it a while, coming home, I noticed that it didn't want to idle as usual, but needed additional throttle to stay running at red lights and such. The exhaust had a more hollow sound, too. Didn't really start "hard", but took a little bit longer, with a little more throttle needed. No big deal, but it started with that particular load of new fuel. So I "drove it out", refilled with better fuel, and all was well. Perhaps this might be similar to what you might need to do?

With no vacuum going to the sensor, the flap in the snorkel remains open, which is what you mention desiring. Also remove the vac line going to the sensor, for cosmetics. Just compress the retention clip to make that happen.

Take care,
CBODY67

Fuel was topped off the day before the trip and the treatment was added. Drove about 200 miles the next day, topping it off again with ethanol free gas at a gas station on the Island at the halfway point of the trip before driving home. It was the day after the trip when the issue started. Thinking it may be fuel related, I topped it off again at my usual gas station but nothing improved.

When I bought the car, the previous owner said he didn't let the gas gauge go below 1/4 tank b/c he was unsure of the accuracy of the gauge so I've done the same. I'm at that level right now so I'll throw my usual fuel in and see if anything changes. Also, will do with the vac line. Thank you!

 

[CBODY67]

On the www.fuel-kits.com website, it has a list of ethanol-free gas stations in the USA. There's also a list of fuel additives and if they contain alcohol. Not sure how recent either list might be, but they can be used as a "guide", either way. There are some informative articles in there, too.

As to the ethanol content, I'm not sure if your state has labeling laws on how much ethanol is in the fuel in your state. There might also be some stations up there which sell E15, which has a different pump decal noting such, than the normal E10 pump label. Something to watch out for!

If you might not have already done it, might be good to plan to replace ALL of the rubber fuel lines as a winter project. The first ReFormulatedFuel tolerant rubber fuel lines appeared in about 1992, with improvements as time progressed into full E10-15 capabilities. The short pieces at: the fuel sending unit (which has the "bridge" contact so the fuel gauge works on it), the short section near the rear of the rh sub-frame section, the section at the intake side of the fuel pump, and then the sections at the fuel filter.

If you do put the car away for the winter, remember to start it every so often (weekly?) so that the fuel lines do not dry out. The rubber diaphram in the fuel pump, even if it's recently new, can still be negatively-affected by E10 IF the fuel pump might dry out, causing the diaphram to become brittle and fail. I read that in another forum about 10 years ago. When you do start the engine in those "down times" be sure to let it run about 20 minutes or so so the engine temp will come up and stabilize, "cooking out" the moisture that might collect in the motor oil and such, each time. Just because the coolant temp gets "to temp" does not mean that the complete engine is at that temp. Which usually takes at least 10 miles of freeway driving to accomplish. FWIW

Take care,
CBODY67

 

[MattfromMaine]

On the www.fuel-kits.com website, it has a list of ethanol-free gas stations in the USA. There's also a list of fuel additives and if they contain alcohol. Not sure how recent either list might be, but they can be used as a "guide", either way. There are some informative articles in there, too.

As to the ethanol content, I'm not sure if your state has labeling laws on how much ethanol is in the fuel in your state. There might also be some stations up there which sell E15, which has a different pump decal noting such, than the normal E10 pump label. Something to watch out for!

If you might not have already done it, might be good to plan to replace ALL of the rubber fuel lines as a winter project. The first ReFormulatedFuel tolerant rubber fuel lines appeared in about 1992, with improvements as time progressed into full E10-15 capabilities. The short pieces at: the fuel sending unit (which has the "bridge" contact so the fuel gauge works on it), the short section near the rear of the rh sub-frame section, the section at the intake side of the fuel pump, and then the sections at the fuel filter.

If you do put the car away for the winter, remember to start it every so often (weekly?) so that the fuel lines do not dry out. The rubber diaphram in the fuel pump, even if it's recently new, can still be negatively-affected by E10 IF the fuel pump might dry out, causing the diaphram to become brittle and fail. I read that in another forum about 10 years ago. When you do start the engine in those "down times" be sure to let it run about 20 minutes or so so the engine temp will come up and stabilize, "cooking out" the moisture that might collect in the motor oil and such, each time. Just because the coolant temp gets "to temp" does not mean that the complete engine is at that temp. Which usually takes at least 10 miles of freeway driving to accomplish. FWIW

Take care,
CBODY67

I do put it up for the winter and fire it up every week. Last winter was my first, so I appreciate the guidance regarding winter storage.

I'll be taking a look at the carb in a bit to check for debris under the needle preventing the correct seal. I know I search this forum and learn a lot from new and old discussions alike and if it looks like this is the issue, here is an article walking you through how to fix the problem.

Needle and Seat – Vintage Muscle Car Parts


- 2245 (same as my 2210) carb rebuild that shows what is where.

 

[MattfromMaine]

I didn't see anything flowing down the carb after shutting it off but as I turned it on and off a few times to look, fuel started to seep right where the needle is located. Looks like that is the issue.

Judging by how dirty this all is, a rebuild might be the way to go since it has to be disassembled anyway.

 

[CBODY67]

From the looks of the fuel pattern on the outside of the carb, it might not be the INTERNAL needle/seat that's not sealing, but the thin metallized gasket between the brass fitting and the carb air horn seeping. Which will, over time, put a fuel migration pattern on the outside of the carb, as pictured. That gasket is basically coated metal that has a bit of compressibility to it, but not very much, but just enough for some additional conformity to the carb casting it seals against.

The 2210/2245 Holley is not a hard carb to rebuild/re-gasket. You might find some small charcoal granules in the bottom of the float bowl. I found those in out '72 2210 when I first took it apart (after several years of use from new). Not sure how they migrated from the carbon cannister into the carb via the bowl vent/evap emissions hose, but they were there. I cleaned them out and it appears they were not causing any problems, other than being where they were.

Thanks for the updates,
CBODY67