Well I thought I was convinced it was vapor lock. Used to happen only as the motor was hot. Now it just seems to happen randomly and more often. Heres what it does…
Idles fine in park. Idles a little rough in gear. When I drive aggresivly and take off faster giving it more gas the symptoms seem to go away. When I just barely lean on the gas to slowly pick up momentum (trying to save fuel and money) It kind of surges or stutters until I put my foot in it a little more. Then when I’m up to speed cruising with my foot barely on the pedal it will surge or stutter a little bit but not nearly as bad as taking off.
Iv’e rerouted my fuel line around the back of the motor eliminating the steel line (thinking it was vapor lock) I have a new fuel pump and I know it’s getting fuel.
My step dad and I have gone through all the troublshooting of the carb. Tried a leaner mix and a richer mix. Tried everything on edelbrocks videos including adjusting the accelerater plunger. since I have 10 lpbs of vacuum at idle and 6 in gear we tryied different needles and springs that edelbrock recommended for my vacuum levels… tried my air mixture screws. took em out and blew air in to clear any debris. Set everything on the carb back to defaults and tried to adjust it in again. and again…
Then we went to check my timing. As we went to point the timing light down at the mark we noticed ever so often the strobe would miss one or 2 times and at the same time my motor did a little shake. Hardly noticable. Then we put the timing light on a different spark plug wire and it did the same thing. Which leads me to think I’m not getting good spark somewhere from the distributor or somewhere before the distributor. We tried a different coil and got the same symptoms. All plug wires are new. Distributor is new. Checked for vacuum leaks and everything seems to check out. starter silinoid is new. altenator is new (from a few years ago) battery is new.
But recently I wired my electric fans and my fuel pump to the silinoid in the key on side along with my coil. It made my tach act weird (reading 1500rpm when the car was really at 1000rpm) and i put up with it for 2 weeks and i finially rewired everything to the fuse block so the only thing ont he key on side is the coil now. and this problem seemed to start a few weeks ago. Maybe I damaged my silinoid and its not putting out a steady electric current?
Iv’e also been having to park my car out on the street and have been removing the rotor from the distributor and or the wire going from the coil to the distributor (to prevent someone from starting it and driving away in the middle of the night)
Maybe I’ve damages the wire by removing it so many times in the last few weeks?
I can’t really think of any other things I may have done to cause this at the moment. If i think of anything else I will add it.
help?
First (hungry-est?) things first: The electric radiator fans should NOT be tied directly to the ignition switch! Rather, feed a heavy gauge wire to the input side of and equally heavy-duty relay, and let the relay be switched on by the ignotion switch. How heavy should the wire and relay be? That depends on the current draw of the fan - how-to articles about using the common 3.8L Taurus on Lincoln Mark 8 fans usually say that they like around 35-40 amps running… “inrush current” when the fan first kicks on can be upwards of 70 amps. That leaves a lot less than nothing to power the ignition! Current through the ignition switch contacts is a lot less than 30 amps, otherwise the 14-16 gauge wire that feeds the switch would have melted down long ago.
At first it only happened when it’s hot, now it happens more often? AFTER GETTING THE FANS ON A SEPARATE RELAY; I’d start wondering if the coil is dying. Might think about getting another coil and see if it changes anything. These are the first two things that caught my attention.
If I was really pressured to come up with another answer; I’d probably go back to the coil. If you occasionally don’t get spark at different plug wires; the points and coil would be pretty suspect.
Another thought: If you have a Pertronix or other “no points” ignition modue instead of old-fashioned breaker points, you may need to go the “relay” route again; as those guys generally like 12 volts+ and there is a “resistor wire” (just like it sounds) between the coil/points and the ignition switch. This LOWERS the voltage to the coil and points, mostly to keep the points from prematurely eroding away due to being fed by a full 12 volts.
EDIT: (This is why I typed “For now” 
) Back to the fan! IF that fan is drawing 40 Amps all the time that it is on, and IF you’re still using a 42 Amp alternator; I’ve got $5 that says your battery is dropping voltage pretty quickly. And that puts you back to not having enough juice to properly power the coil.
Okay, I’m out of possible troubles.
For now.
My old Ford tractor had that problem. It would purr like a kitten until it got hot, then start to miss and down on power. Talked to an old farmer, he said, sounds like the coil. Sure enough that was it.
10 inches of vacuum isn’t nearly normal. Does this car have a cam replacement?
Might want to check the firing order. Almost every replacement cam has the 351 firing order. I believe that 6 positions are the same, the 289 firing order will run with the updated cams.
Check the distributor vacuum advance, might be stuck or not functioning.
Bad or old plug wires?
i have the fans on a seperate relay but at first i had it also getting power from the ignition on. i now have it ran to a seperate location on the fuse block all goes through a relay and a braker. i dont think thats my problem.
tried a different coil…same symtoms…Going to look into a crane or msd ignition system.
also plug wires are all new like i said.
and i dont think my vacuum advance isnt working right. ive had it go out on my before and i know exactly what that is like. unless it is on its way out and isnt super obvious but just at slow take offs. will look into that.
I want a crane ignition system anyway so I am going to add that along with a new coil and see what happens. if it doesnt solve my problem at least i eliminated that as the problem.
and yes i have a cam in it. Im going to call my engine builder and ask him what he thinks about the firing order thing. i have it hooked up as a 289 firing pattern.
idk. Edelbrocks site said if you have a cam and less that 7 lbs of vacuum to change the springs to a different color. tried it and no luck. but i wasnt able to try one of the springs that edelbrock suggested. my engine builder said he has a kit that i can pick through. I just did some work for him for free so Im gonna see if he can solve this.
over all the car drives pretty good though.
Any chance this is your first car with a big cam? That lumpy idle is not a good thing for smooth driving. Also, with a cam you need to bring idle speed up to probably 900 rpm or so.
It’s my first car EVER. haha.
Yeah I have the idle up pretty high already. But ill bump it up a little more and see what happens. Maybe it will make the problem less noticable. thanks.