GT500 stalls at stop lights/signs

My car (HiPo 289) does the same thing, and I have replaced all the same items, except I haven't replaced the carb yet. Mine only behaves like this when it is fully warmed up. I sometimes have to put the clutch in and tap the gas as I approach a stop.

 

normal. coolant travels from the engine to the top radiator hose, through the radiator & the bottom hose, then back to the engine.

Z. Ray

 

My 66 350 died at a stop occasionally and I traced it down to the carb. area. It was the little diaphram (sp?), It might be called a dash pot ( I'm probably wrong on the name as it was 30 years ago or so) but when the throttle lever returns to an idle position, it contacts a spring/diaphram valve (dashpot?) and allows a less abrupt return to idle. I know I didn't explain this very well, the the part bolts to the left front carb mounting stud between the carb and the hex nut. My Shelby was an automatic but I think the same part was also on standard trans models as well. Hope this helps,
Mike

 

When you started explaining the symptoms of stalling my first thought was the dash pot like Mike Christie referred to. If you are running a different cam the engine vacuum may be low and not allowing the power valve in the carb to function properly. When the vacuum is low the motor you would have a hard time adjusting idle. Its like the timing is advanced and takes a while to return to normal after you rev it up. Very annoying!!!

 

Looking at your first post, I don't see that your cart is overheating? If it is not overheating, then don't worry about the hose heat differential.

Secondly, with an automatic you need a dash pot on the carb, do you have one? If you don't have a shop manual, get one ( available on CD ) & set the dash pot yourself.

Also if your floats are not in proper adjustment that can cause the dying when coming to a stop. Have you checked that?

good luck, and keep us posted.


Z. Ray

 

Oregon Shelby, you mentioned that you had your "carbs" adjusted. Do you have more than one four barrel carb? Is this a big block or small block engine?
Mike

 

Hi- if this is a automatic car, based on my miserable experience over a 2 summer period, you have a bad converter in the tranny. If its a 4-spd - keep chasing all the things already mentioned. Only took those 2 years to figure mine out and probably $1000.00 of money wasted away on all the wrong things.
Good luck

 

Just to clear up some issues.
The engine is a 428 with H/M intake with two 4 barrel carbs.

 

OK, assuming you have two Holley 600 or 650's. If memory serves, I think the front carb primaries are responsible for idle. If so that is where the dashpot should be located. Make sure it's there and working. This is the simplest place to start, as well as making sure all the basic tune up, plugs, points wires timming etc; are all good.
Question, do you notice any black smoke when it's stumbling and trying to idle, like an extremely rich mixture, coming out of the tail pipe? If so, I would check the carb floats like zrayr mentioned.
Also, check to make sure you have good manifold vacuum.
Best of luck,
Mike

 

Based on the original post, I interpret the problem to be that it won't idle when it's in gear, not that it won't idle at all. Unless I'm reading the description wrong, he puts it in neutral to keep it running, then when he's ready to go, he rev's it and slams it into drive to avoid stalling.

If it's idling in neutral, that eliminates quite a few of the suggestions for what to check (although they're all very good and informed suggestions).

Perhaps I'm wrong in my interpretation... can you provide input, Brian?

Josh

 

Brian,

From your description I assume that your car is an automatic, but have not seen a definitive statement to that effect (but of course I may have missed something). Is it an automatic?

 

It really sounds like you have a vacuum problem somewhere.
Check all vacuum lines for any leaks.
Are you running the spacer between carb and intake to keep heat from causing vapor lock?
Might also check the gaskets and mounting of carb to make sure it's not sucking air between intake and carb.
Is your vacuum advance on the distributor working properly?

Russ

 

My experience with vacuum leaks is that they cause a fluctuation in idle and it would be independent of whether or not the car is in gear. Regardless, the easy way to check for a vacuum leak is to spray carb cleaner around the base of the carbs and around any vacuum lines connecting to the manifold (keep in mind carb cleaner can be harsh on painted surfaces) being careful not to let it get sucked in the air cleaner. If the idle speed goes up, vacuum leak. If it were my car, I wouldn't check that though because it really doesn't sound like a vacuum leak to me.

My guess is corbins had it right, and the problem is in the transmission. If the torque converter isn't functioning properly, you'd have the problems you've described. If it were my car, I'd take the shade tree mechanic approach to diagnosing the problem, and try to flutter the throttle JUST enough to get it to go in gear without dying, then I'd see if I can run the RPM's up just a little, to say between 1000 and 1250, while applying the brake. If it feels like your really having to lay on the brakes to keep the car from trying to go, then I'd take a closer look at that torque converter.

Josh

 

Brian, if your toque converter is dying. Check your transmission fluid for a burn't smell, and metal particles.
Kenny

 

It also be the fuel is boiling in float bowls. Does your card have a dash pot on it if so checkec adjustment. check float level with car running pull side plug if the fuel is running out that is to high. You want it to when you rock your car a little bit the fuel should just start to run out. Or try your fuel enrichement
screws, if you have a vacuum gauge hook it up below throttle plates turn screws in till engine starts to run rough then back out slow to you get you highest vacuum reading. Then do the same with the other screw.

 

Hi to all! Just a thought on stalling after reading all these posts.Have you ever tried to stop useing the handbrake?If there is a vacuum leak in the booster,it may only occur when you apply the brake pedal.It is easy to try,and it will let you know if it is a booster problem.One other often overlooked vacuum line is on the transmission modulator valve,make sure you check it.Go over the simple stuff first.....it is important to work in steps,and not jump around.Good luck and please keep us posted