61bluebird
Well-known member
hey got a little problem with my 1 falcon,at part trottle driving down the road i have a little miss,cant figure it out . any advice will be helpful
stumble
- Thread starter 61bluebird
- Start date
Mercury Mike
Famous Member
Timing timing timing.
If you are running points, Hook up a dwell meter and make sure the reading is stable through and around your crusing RPM. I have seen dizzys wear and only show up at certain rpms. It was very obvious on the dwell meter and when I removed the dizzy. A rebuilt with new points solved problem. This was on a 1950's 4cyl ford tractor.
If you are running something with electronic ignition (DUI, or DSII) check the pickup coil with ohm meter and use vac pump to operate advance plate and make sure reading does not change, if it does could be a broken wire. This was a fairly common problem with 74-81 GM Hei's when they got older and some miles on them. Im not sure if it is that common with the fords since the wires are a bit larger but its an easy check.
I had a 84 Chev V8 that had a a stumble like that and thought it was a locking torque converter issue. I dont remember why but I checked the dizzy and found the rotor had come loose (that vintage GM Hei rotor was held on with 2 screws). The center contact in the cap was almost gone and the top 1/4" of the rotor tip was worn/burnt off. I drove it that way over 100 miles and over all it ran fine. The ford rotors cant really come off like that but if that little clip wears out, breaks, or is missing the rotor can flop around a bit, I found several wraps of teflon thread sealing tape will keep em snug.
How bad a stumble? Does it happen cold and warm? Do you have auto or manual choke? If manual try giving it a little choke when it does it. If auto try and get it at that speed before it warms up and see if there is a change.
If you are running something with electronic ignition (DUI, or DSII) check the pickup coil with ohm meter and use vac pump to operate advance plate and make sure reading does not change, if it does could be a broken wire. This was a fairly common problem with 74-81 GM Hei's when they got older and some miles on them. Im not sure if it is that common with the fords since the wires are a bit larger but its an easy check.
I had a 84 Chev V8 that had a a stumble like that and thought it was a locking torque converter issue. I dont remember why but I checked the dizzy and found the rotor had come loose (that vintage GM Hei rotor was held on with 2 screws). The center contact in the cap was almost gone and the top 1/4" of the rotor tip was worn/burnt off. I drove it that way over 100 miles and over all it ran fine. The ford rotors cant really come off like that but if that little clip wears out, breaks, or is missing the rotor can flop around a bit, I found several wraps of teflon thread sealing tape will keep em snug.
How bad a stumble? Does it happen cold and warm? Do you have auto or manual choke? If manual try giving it a little choke when it does it. If auto try and get it at that speed before it warms up and see if there is a change.
61bluebird
Well-known member
ive checked the points on a dwell meter(not at different engines peeds tho ill check that next)im running a rebuilt 70 dizzy ,ill post back when i put the meter to it today
61bluebird
Well-known member
ive checked the points on a dwell meter(not at different engine speeds ill check that next)my dizzys a rebuilt 70 unit from a parts store illput it on the dwell meter and post my results at different engine speeds
61bluebird
Well-known member
im running a carter yf off of a 70 maverick
If it idles good that would seem to rule out the usual stuff like vac leaks and valve train issues....
Pull a coil off another car for a test? Long shot but if you have another one laying around you could then rule out ignition as a possibility.
Have you messed with float levels? Maybe a weak fuel flow for some reason? Maybe its ok at WOT because the rpms are working the pump fast enough to compensate but at crusing speed the rpm are low enough but the demand is still high so its starving a bit? Do you have any other main jets to try?
Pull a coil off another car for a test? Long shot but if you have another one laying around you could then rule out ignition as a possibility.
Have you messed with float levels? Maybe a weak fuel flow for some reason? Maybe its ok at WOT because the rpms are working the pump fast enough to compensate but at crusing speed the rpm are low enough but the demand is still high so its starving a bit? Do you have any other main jets to try?
