Low idle stalling in a 1969 GT

[1969GT 10]

Hello everyone,

 

I'm a new user so bare with with me.

 

I recently had the torque converter replaced in my mustang. When I picked it up it was virtually out of fuel, we put enough in to safely get me to the gas station. While we had it idling it was sputtering, kind of a quick die then rev back to life. We thought it was air in the lines. While driving it to the gas station it did the quick stall then came back to life, then died when I entered the gas station lot. Started it, got gas, and drove home. No problems until I got to my street and was idling down the street, it was sputtering again, I parked it and let it idle in the garage. It kept sputtering then died, restarted it, did everything again and died.

Our thought is, either the air filter was cranked down to much causing problems, not likely though. Or, the carb is dirty and its not getting enough fuel for whatever reason while your is your foot is off the excelerator. It has an Edelbrock Carb in it.

Any thoughts? Is there a good cleaner to add to the fuel to try and clean the carb? I do add Stabil fuel stabilizer every fall. The guy also checked the transmission connections to the engine in case a hose was off apparently everything is where it should be.

Thanks, appreciate the help.

[MustangGT 11]

Dirty fuel filter -- I would start there and then check the carb bowls. As good as place of any to start and no very difficult.

[Mike65 475]

You also might want to check/replace your fuel filter if it was run very low on gas you might have partially plugged the fuel filter.

[1969GT 10]

Thanks for the info, I will start with the fuel filter. Quick question on the filter. The current filter is a clear glass or plastic tube with the filter element in it. I checked O'reillys as well as CJPonyParts, it looks like everything is a solid metal now. Does it make a difference what can be used? 351 Windsor H code with an Edelbrock 4bbl carb.

 

Thanks again.

[MustangGT 11]

Doesn't really matter -- the clear one helps to confirm fuel is flowing and it is sometimes easier to see how 'dirty' it is. Check around and you should be able to find another clear one if that is what you want.

Edited July 13, 2013 by MustangGT

[1969GT 10]

I bought a Wix fuel filter #33046, since it has a threaded end I assume it would thread into the carb. At this point I am opting not to do that, the old one is clamped between to fuel lines so I am hoping I can do the same with this one and the threaded end will not cause any problems. I imagine the threaded end will go towards the carb, there is an arrow on the filter as well.

[Hoover 12]

You might have water in the gas tank, or old gas in the tank that causes problems. Put on new gas filter, and check the idle speed on the carb.

 

You might need to install a carb rebuild kit, and clean out the carb to prevent this from reoccuring.

[1969GT 10]

Here is an update on my issues.

 

I replaced the fuel filter with an identical filter. The old one did have some debris in it. After starting the car it ran for a minute or so and died. Tried carb spray and it died, tried again with same results. I used a screwdriver and rapped on the carb at the point where the fuel line connects to the carb. On the metal portion of the carb. It ran fine for about 15 minutes then started to sputter. Around the 20 minute mark it was gasping and sputtering so bad I just turned it off. I am running a Edelbrock 1406 carb in it. Is there a built in filter or screen that may be plugged? Rapping at the fuel line junction did something, possibly settle sediment. Whats my next step?

[jmlay 80]

Check all of your vacuum lines. It might be a good idea to mark them all & plug the hose & the port to see if it stabilizes. IF it does then reconnect one at a time until the stumble returns. Was the trans modulator replaced, they can leak if the diaphragm is damaged.

[1969GT 10]

The only thing that was done previous to this problem was a newly built torque converter installed. Otherwise the engine or carb were not touched other than reconnecting the transmission and lines.

[Midlife 814]

Isn't there a vacuum line to the transmission? I wonder if that may be the cause of the problem...

[Mike65 475]

Also check the vacuum modulator that the vacuum line goes to, I have seen them leak. Pull the vacuum line off the modulator & see if trans fluid is in the vacuum line, if so that is the source of your vacuum leak.

[1969GT 10]

If I determine it is a vacuum leak from a hose, I assume I will just need to change the hose and that SHOULD solve the problem, unless it is in the transmission itself?

[jmlay 80]

Correct.

 

If I determine it is a vacuum leak from a hose, I assume I will just need to change the hose and that SHOULD solve the problem, unless it is in the transmission itself?

[1969GT 10]

Here's a brief update.

Started the car today and it was still sputtering and not stay running. Checked for any loose hoses, I found two doing a visual, one runs from the back upper center of block and goes below the car. The hose went to a metal line, the hose was not on very well and rather loose, it was a little short as well. Also there is a hose that runs from the front of carb and goes into the passenger side valve cover. It sits loose in a rubber grommet of some kind.

 

I did tap on the carb fuel inlet again and it ran for about 15 minutes and then went down hill from there. Why would it run fine tapping on the brass or copper fuel inlet, only to suffer same symptoms after 15 minutes or so? Bad fuel inlet fitting grommet?

It was hard to tell under the hood with the car running, but I thought I could hear a hissing sound, possibly from the fitting in the back of the block.

 

I have a couple pictures but not sure how to attach them without using a link of some kind. One is of the fuel inlet, the other is of the point where I possibly hear hissing and the first loose line. If your interested in a visual I can email them.

[1969GT 10]

Here are the pictures.

[Mach 351 10]

I’ve had modulator valves go bad before, but they usually started shifting funny beforehand. If it’s shifting fine your modulator valve may be fine but have a leak in the hose (at either end or in the middle). What’s your idle set at? Idles often jump up and down with vacuum leaks. You could just disconnect the vacuum hose at the intake and cover it. None of your vacuum run things will work, but if your idle improves it isolates the problem to a vacuum leak.

[1969GT 10]

No problems with the shifting at this point. Replaced the Torque Converter, this started up right after that. I have my idle set a bit higher than normal, but not so high it diesels when turned off. I tried increasing it a bit to see if that helps but it did not.

If you could upload videos I could give everyone a good idea what it sounds like. I don't think that's an option on here.

[Max Power 74]

 

I did tap on the carb fuel inlet again and it ran for about 15 minutes and then went down hill from there. Why would it run fine tapping on the brass or copper fuel inlet, only to suffer same symptoms after 15 minutes or so? Bad fuel inlet fitting grommet?

It was hard to tell under the hood with the car running, but I thought I could hear a hissing sound, possibly from the fitting in the back of the block.

 

 

It sounds like you learned about the old trick of tapping on the carb without having any real idea what it actually does.

 

Tapping on the carb was an old truck that was used on cars that have been sitting a while, and it is a method used to loosen a stuck float, or needle and seat, more specifically. With cars that would sit a while, the needle would stick in the seat and tapping on it would let the needle drop, freeing up fresh gas flow.

 

It is more unusual for it to fix a car that has been running on and off, but I suppose there are reasons the needle could be getting stuck in the seat. I think it is safe to say that if all connections vacuum wise are good, and all filters are current, it might make sense to look inside the carb. This is one situation where Holley has an advantage, with their float bowl sights.

 

Another thing to check for is of the fuel line is touching anything how and you are getting percolation/vapor lock. Tapping wouldn't really help that, but it is something to look for.

[edwards54 15]

If you have them I would check your points....take of the distributor cap and see if there is dirt, carbon or something else in there. I went through similar issues last year. I changed filters, cleaned the carb, and finally took of the cap. It's a five min fix and worth a look

[prayers1 153]

Maybe a long shot, but is there a vacuum line going to the trans that was never reconnected by the shop? If not, and you already replaced the fuel filter. Try blowing out your fuel line, maybe you sucked in some dirt when draining the tank.

 

My second guess would be debris in the carb.

[1969GT 10]

Thanks for all the input, more things to look at if nothing else fixes the problem. I did remove the fuel line that goes directly into the carb. After doing that the car will not start at all. Tried starter fluid and not even a bang. No Spark? Pulled a plug and it was black as black can be, so changed all 8 thinking they were all bad. Nothing. I did find a wire that runs from the distributor to the ignition coil i'm guessing. It was basically hanging on by 1 strand. I will reattach and see if that is causing the failure to fire problem. Is it possible that the wire and fouled plugs could be the reason for all the problems?

[Tgriffin91 27]

I had a similar issue. Mine was the needle in the carb not closing because the wire clip that holds it in place came loose. You just have to pop the top of the carb off and check to make sure it is held in there.

Might help might not.

Good luck!

[1969GT 10]

Here is an update since my last post.

 

New plugs installed as well as properly reattaching the small black wire that runs from the distributor to the ignition coil. Started the second time. Ran it for about a half hour and it had one sputter about a minute in, otherwise it did not have any issues while idling. Up'd the idle a bit but dieseled when I turned it off. Just need to idle it down is all.

Am I crazy or are my problems from fouled plugs and a bad connection off the ignition coil? I won't ignore the fact that there may be a vacuum issue or a carb or dist. problem. At this point it seems to run fine. Just very rich.