Diagnosis: Engine cutting out at low speed when warm.

[kuhlou]

200 cu in six, stock carb overhauled by local shop last winter before storing, installed power boosted SSBC discs, installed vacuum line from intake vac dist block to booster. Starts fine, runs fine at low speed and highway speed, run into city (about 10 min), and will cut out and die when cruising around town. Difficult to restart, rev motor a bit and get up to highway speed and runs fine. Cuts out again at low speed pulling into the driveway. Any suggestions as to where to look for the problem? Also installed pertronix electronic points last summer, they seem to have been working fine. I've had the car for a year, so real new to this troubleshooting thing. Thanks. :

 

[ludwig]

Make sure your choke is coming all the way off after the engine is warm. If not, it will bog out and die when you press the accelerator. There have been several recent strings about chokes. Check them out with the 'search' function.

You should give your location too as well as which carb you have. The problem might be related to where you drive, like above 6000 feet or close to the Arctic Circle (like Monsieur JackFish). Maybe you don't need a choke at all, for instance.

 

[kuhlou]

will check it out, carb is stock on 66 mustang, one barrel, don't know the make, location Byron, MN, was about a 50 degree day which is ordinary for this time of year. Thanks!

 

[Bort62]

Stalling @ low speed w/ engine warm tells me that your idle speed is set too low.

Fast Idle is keeping it alive when cold, but once choke opens - low idle speed kills it.

It could also be insufficient ignition advance doing the same thing, but less likely IMO.

Try upping the idle speed slightly.

 

[grocery getter]

40 plus year old car, get used to troubleshooting.

do a search on petronix and see what you come up with...

are you getting any pinging when you accelerate ?
( when it's running poorly )

 

[kuhlou]

to troubleshoot further. Thanks for the helpful replies, now to get the sun to shine and the roads dry here in MinneSNOWta!

 

[wsa111]

Also installed pertronix electronic points last summer,

If you installed a pertronix II that is probably your problem.
The pertronix II is a POS.
The pertronix I is a great unit.

What do you have?? Bet thats your problem. Bill

 

[page62]

Sounds like you have vapor lock problems:

1. Check your carb float height. This is critical in preventing carb boiling.

2. Make sure the fuel line isn't running anywhere close to the exhaust manifold or other sources of heat.

3. Do you have the coolant hose running through the carb base? If it isn't (but it should be), try reconnecting it. If it doesn't help, you can always pull it off again.

 

[kuhlou]

thanks again for all the advice, will get after if it ever warms up again here.

 

[kuhlou]

adjusted the choke, the linkages are sort of old, a bit rusty. Can they be lubricated? Runs better, still misses a bit when idling. Runs down the road fine. Sputters a bit when cruising at low speed thru town. Ignition is pertronix I.

What is correct procedure to adjust choke? I let car warm up, then adjusted choke to be wide open when warm. Will see if it works when cold. We are still having cool mornings.

I need to unhook the "carb heat", will get to that next.

Plugs were full of carbon. They are Autolite 46. I got the performane six book mentioned in this forum and I see they suggest with electronic ignition a hotter coil going to one step cooler plug and wider gap. Ths is a california smog pump car, still intact. Any guesses on which plug to use?

Also read that timing should be advance 5 degrees from normal. Any suggestions as to the stock and adjusted timing. Procedure for this would be appreciated also.

Carb is the stock autolite 1100, from what I can tell. I fooled around with a vacuum gauge for the first time today. when warmed up and idling, the vacuum was about 16. Is the adjustment screw the one at the base of the carb? I fiddled there just a little, but didn't seem to make much difference in the rough idle.

Seems to accelerate well on the road. It's the low speed and idling that needs to improve. Thanks for any comments and help.

I've debated on taking off the smog stuff. This is a real nice original california six banger that I imported to MN, including the black plate, so I hesitate to rip 'er apart, including the smog pump. Am I looney, does the smog stuff need to come off? Or, leave as is and preserve the uniqueness of this vintage aqua stang convertible?

Many thanks, appreciate ALL comments.

 

[Bort62]

No need to take the smog stuff off. People will tell you "rip that crap off of there!!" but that's just ignorance. For what it sounds like your purposes are, it's not hurting anything.

Sounds like you may need a carb rebuild. When is the last time that was done?

 

[kuhlou]

carb was just rebuilt, my local shop guy "sent it out" for a rebuild, and he reinstalled it. I'm sure he had the choke adjusted wrong, which was at least part of my problem.

 

[kuhlou]

I measured the vacuum at idle, with the engine warm, off the intake vacuum port. Is this the correct place to measure the vacuum? How much vacuum should there be?

I'm headed off for a new set of plugs, I'll also check for vacuum leaks.

 

[ludwig]

That should be the right place. Not the vacuum advance hole. You want to draw a minimum of 18 lbs vac. More is good; should be steady and not fluctuating.

 

[kuhlou]

do I understand correctly that advancing initial timing 5 degrees or so will raise the vacuum reading and help with the running too rich problem?

Also, what is the correct way to adjust the automatic choke? I seem to either get it wide open or shut, with no in between.

Also, read that with the pertronix ignition and coil, to go to the next lower heat range plug and gap them wider. The stock plug is the Autolite 46, which is currently installed. My auto parts store did not know what the next lowest heat range is, can anyone tell me the answer, or where I should look for the answer?

Thanks for all the help.

 

[kuhlou]

Who carries the Flowmasters for the six? just curious. If I ever get the current issues solved, then I'll start thinking about what's next!

 

[grocery getter]

do I understand correctly that advancing initial timing 5 degrees or so will raise the vacuum reading and help with the running too rich problem?

Also, what is the correct way to adjust the automatic choke? I seem to either get it wide open or shut, with no in between.


Thanks for all the help.

I adjust the choke stone cold. set it where it is almost all they way closed. then go from there. make sure it is fully open when hot.

 

[ludwig]

wrote:
do I understand correctly that advancing initial timing 5 degrees or so will raise the vacuum reading and help with the running too rich problem?

Also, what is the correct way to adjust the automatic choke? I seem to either get it wide open or shut, with no in between.


Thanks for all the help.

I adjust the choke stone cold. set it where it is almost all they way closed. then go from there. make sure it is fully open when hot.

What he means is, with the engine stone cold, like first thing in the morning, take the air cleaner off. Observe the position of the choke plate. Next, make sure the choke plate moves freely throughout the whole range of motion.

Then loosen the black adjuster cap (but without taking the screws out). Turn it clockwise to open it (I believe) and the opposite way to close it. Turn the adjuster so that the choke is closed all the way except for about 1/8" and only that far without any extra pressure. Now it will pull off if the coiled pull-off spring is anchored properly inside the adjuster cap. Start the engine and wait to see if it opens as the engine gets warm.

If it doesn't pull off, adjust it to loosen some. If it runs properly, is clean inside and out, none of the races, pivots or slides are bent or dirty, the heat riser tube is open, the coiled spring is not broken, the port between #3 and 4 in the exhaust manifold is not burn through and no soot is filling the little bitty hole in the carb wall, you are good to go. If not, clean all that stuff and try again - tomorrow morning.

 

[kuhlou]

gosh! should be a piece of cake! ) Appreciate the advice very much. I notice all the levers and etc between the choke and the carb are somewhat rusty and dirty, but do seem to move. Is it worthwhile to squirt them with some sort of lubricant? Or, take apart, clean and lubricate, Or, just replace those parts?

many thanks from this newbie.

 

[Rustang Racer]

The screw you were adjusting on the bottom of the carb was probably the idle mixture and not the idle speed. The idle speed screw is somewhere near where the throttle linkage meets the carb. It is a screw that physically holds the throttle linkage open and will have an immediate effect on idle. Adjust the idle speed when the engine is fully warmed up and the choke is fully open. When that is set, go back to the idle mixture screw on the base of the carb. Turn that screw in and out until you find the sweet spot where it idles the fastest. If the idle is too fast when you are done, turn the idle speed down. Then go back and adjust the idle mixture again.