problem with a 67 mustang
 

okay, im new here and i know theres probably a rule about using search before posting, just to let you know i did and there was a similar post but it didnt go in dept enough.

ive spent a bit of time searching for an answer for this question and im hoping that bouncing the ideas off people that may have experience will help.

i have a 67 mustang coupe, with 50k miles on the engine/trans.
its a 289 with an auto that hasnt been rebuilt. it ran fine till a month ago when it started struggling in gear, it will idle and run fine in park and neutral, but in gear, it will idle horribly, and even stall. once moving it will once again run fine, but if you are in gear and use the brake, it will attempt to stall, then will hiccup, (the brake pressure will drop a bit, causing the car to roll foward a tiny bit, then will catch again and the engine will compesate, this happens every time the brakes are used. so any suggestions? id greatly appreciate any help

How does it take throttle when it's not in gear? If it is still revving all right, you can probably eliminate a fuel problem.

You may want to check the timing. Sometimes an engine will run fine without a load, but will act up under load if the timing is out of whack, causing a dip in horsepower; if it's enough out of whack, it can cause stalling.

It could also be a brake problem. If the emergency brake cable is adjusted too short, the shoes will drag in the drum (I'm assuming you have rear drums), and when you have it in gear attempting to move, the engine has to compensate for the extra drag, causing it to stall under low rpms. Then again, one of the springs that hold the shoes around the spindle could be stretched or broken, causing the shoe to ride the inside of the drum when the brakes are not engaged as well. (That should only happen in one direction though; do you have the same problem in reverse?)

If the problem was with the transmission or the rear axle, I would suspect you would have some noise to go along with your stalling problem.

re:
 

it will rev fine and seems to run quite happily as long as its not in gear. it will handle acceleration fine until the time you hit the brakes.

it does this in both reverse and drive, whenever the tranny is locked in to place. this only happens when coming to a complete stop, you can slow down to about 5-10 mph before this starts
the E-brake cable is non existent on this car, its heater core leaked while it was in storage and rotted the floors to nothing, so when the floors fell through, so did the support to the brake cable, (it on my huge list of things to fix) the brake light is on, in the dash, the previous owner was a mechanic and swapped all the brake lines and fittings, and rebuilt the brake housings. so im thinking its simply linked to the proportional valve being uncentered, the rear wheels will lockup well before the front stops rolling. when this last ran it was very warm, around 80 degrees, this started when it started to get colder, do i have to adjust the carb for weather differences?



also when it does stall, it doesnt just labor like stalling a standard trans, it kinda struggles and will drop rpms slowly, then sound out of tune when the rpms are about to drop. but theres no noise from the trans or the rear, it just simply quits. even when its really close to stalling, its usually able to stay running if i let off the brake or kick the gas a smidge,

thanks for your thoughts, i really appreciate the help, im not a gearhead, mostly a tinkerer, i got the car for around 2000$ in running shape, with alot of new mechanics already on the car.

Sounds like ignition or fuel. First make sure the timing is right and that you are getting a good spark. If not that then start playing with the carb. You do not need to adjust for temp change but you do for significant elevation change. Also make sure your fuel filter is not clogged.

Does the car run different when the engine is cold vs warmed up?

Give the car a good tune-up. Points, plugs, plug wires, cap and rotor. Check ignition timing and dwell.

If the above doesn't solve it look for leaking vacuum lines.

Was their old fuel left in the carburetor when the car was stored? Did it build up varnish in the carburetor?

ill have to check for the timing, it could be a issue. as long as its reasonable that the timing would change that much over a few month to go from running great to stalling,

@cj2112, the carb was one of the items that was cleaned and tuned heavily, around 2-3 months ago so i dont think thats an issue, the plugs wires, rotor and cap look brand new. also can vacuum cause this much problems? i know for a fact that a few vac lines are missing, (ac unit, heater, and dash stuff,) the lines just dryrotted apart.

@kinsaj, ive thought about the fuel filter, but cant seem to find one on the car, any idea where it should be? the last owner did replace alot of the fuel lines and added a brand new tank,pump and filler hose, ive traced the fuel lines all the way back to the tank and havent seen one, last i can think is tank mounted?

thanks for the replies.

So we've likely ruled out the carb, rotor and plug wires. The cap could have a hairline crack, but for now let's assume it's good. The timing could have changed that much if the distributor moved. I'd also check the dwell, and the condition of the points as well as the condition of the cam that operates them.

It is unlikely that the fuel filter is tank mounted. It is typically an inline filter found on the supply line for the carburetor. No telling what the previous owner has done though.

Vacuum may cause this, I am unsure if the advance on your distributor is mechanical or vacuum operated, if it is vacuum operated then vacuum problems might cause this.

sounds like timing or vacuum... and I do not have much experience with either as I deal primarily with diesels and bikes. A place to start would be to hook up a mightyvac up to the vacuum line and see if it holds vacuum, if not diagnose and repair leaks.

If the car has the Autolite/Motorcraft 2 barrel, the fuel filter should be threaded into the carb. Wix #33046.
http://www.wixconnect.com/images/filters/2044_1.gif

The loss of performance when applying the brakes, assuming power brakes, points to a bad diaphragm in the booster, a leaking brake booster check valve, or damaged vacuum lines.

You should hunt down the vacuum sources for all of those missing, disconnected or dry-rotted vacuum lines and make sure they are all reattached or plugged off. Vacuum leaks = lean condition, at the very least. If you aren't getting consistent vacuum to the distributor advance (it is vacuum controlled, if still original), the brake booster and the transmission modulator, you won't run smoothly, stop reliably or shift at the proper speeds.

When you think you have all of those handled, get yourself a decent vacuum gauge. At a source off the base of the carb, you should get very close to 22 inches of vacuum at idle.

thank you for the pic of the filter, when i get a chance i will see if its there, seems perfectly logical. the carb is the 2 barrel with the 289 engine. but i do not have power brakes, which is what confused me, what would manual brakes have to do with the engine stalling?. im going to swap most of the lines out since almost everyone i look at is in terrible condition and retest the engine. will keep it posted. thanks to all for the info so far

I'll ask a couple of seasoned professionals for their thoughts on this. From your description of the symptoms, I was surprised to find out that you had manual brakes.

getting back to working on the car
 

I'm very sorry if i shouldnt have restarted this thread but i wanted to tell people the new information i have about this car now that i am finally getting to work on it.

There is no fuel filter on this car, the previous mechanic has jury rigged new lines and in doing so he has removed the area where the filter goes. can this cause clogged jets? this car was run for several hours without the filter. can this be a fuel pump problem? I was told its a mechanical fuel pump and that they can get old and tired.

So, any ideas? also a Thank you goes to everyone who has contributed so far.[COLOR="DarkSlateGray"]

Yes, not having a fuel filter can cause clogged jets. Especially when you take into consideration that your fuel tank has almost 45 years worth of sediment in it.

Yes the fuel pump is mechanical, it runs off of a lobe on the cam. The fuel pump has a rubber diaphragm that that will eventually wear out.

Can you bring the RPMs up slowly? If you can, then I'm gonna guess you have a vacuum problem that is affecting the vacuum advance on your distributor. If you cannot, then you are not getting fuel into the engine.


The only other thing I can think of, and this is highly unlikely, is a clogged exhaust system.

sorry, let me clarify, some of the question was flawed due to me and some new information.
The tank and lines are new, the fuel filter is new (yes i found the filter, sorry cj2112, my fault) the carb has been cleaned, the plugs and wires are new, the distributor cap and points are new and just fixed all the vacuum lines so theres no more leaks, i get around 20psi steady from the lines, and the fuel pump is pushing around 5psi.

Again:
Can you bring the RPMs up slowly? If you can, then I'm gonna guess you have a vacuum problem that is affecting the vacuum advance on your distributor. If you cannot, then you are not getting fuel into the engine.

The vacuum advance on your distributor could be bad, or you could have vacuum lines routed improperly or missing all together.

You could have an accelerator pump bad, or clogged jets in the carburetor.

Have you changed the air filter? It sounds like you've eliminated vacuum (my first guess), and spark. It could be you're not getting enough gas, but it could be you're not getting enough air. Or you could be getting too much air from a leak in the intake system (manifold gasket leak, warped manifold, etc.).

@ cj2112, as in slowly putting the gas in and bringing the rpms up? then yeh, it will smoothly go from idle on, i have replaced most of the vacuum lines, one issue i see is that ive heard that there shouldnt be any vacuum at the carb port for the distributor at idle, it seems to be 8psi at idle, also i know timing is likely off since it will slightly backfire in idle. the distributor is new, so are the sparkplugs and wires. also, this car spews black carbon dust out the exaust, im guessing this is linked to the timing issue but since i cant seem to locate the timing marks.... like i said, this runs fine in idle but will run rough in drive or reverse, but this seems to go away time and again, it ran fine for a few days then started doing this again.

If it is spewing black smoke out the exhaust, that is unburnt fuel. I think we've ruled out a fuel delivery problem. If you have timing issues, this will cause it. I still think you have some vacuum lines improperly routed, or a bad vacuum advance. Fix the timing issue (is it a new distributor, or just a new cap?), your distributor could be a tooth off as well.

i think its a new cap, how can i check the vac lines? the distrib being a tooth off doesnt connect, it ran fine for 2 months with over 100 miles before doing this, and it seems after tinkering with the carb, the vac lines, or a mess of other things, it will go away for a day or two and come back another. clogged jets wouldnt cause this would it? the previous owner ran the engine for a while with no air filter or cover on the carb and the hood has rust particles coming from it, would they somehow get in to the jets? sorry if i sound clueless, like ive said, im no mechanic, just a tinkerer, i really appreciate the ideas that people have given me.

I don't think it's a problem with the jets. If they were clogged, you wouldn't be getting too much fuel, you would not be getting enough.

There should be a vacuum line routing diagram available on line. You might be able to find one HERE