Hi everybody:
Just comeback from a highway cruise, didn't expect it will get worse after changing all these parts

New 1 brl Carter YFA ( from Hong Kong through Ebay ). I enlarged the mounting holes to fit on the intake studs.
New fuel pump (it pumps gas)
New wires
New cap
New rotor
New coil ( I have doubts on this thing)
New ignition module (Petronix), didn't have a problem with the old one since the last 10 years
New plugs
New fuel filter installed between tank and fuel pump

Timing adjusted to specifications.

Still getting rough idle, hesitation on acceleration or poor accel, and missing too. sometime it eases out as I let off the gas and accelerate slowly again.

How do I know if it is a fuel or electric problem?

I cannot think of anything else, need your help and advise. thanks.
forgot to tell you it is a 1966 F100, I-6, 300 FE

 

have you done a compression check? i dont know how bad its hesitating but i had a similar issue with the addition of a nice backfire and it ended up being a sticking intake valve.

 

You just reminded me with one thing:

I did adjust the valves before putting all those parts, and I thought I lost count just let go, do you think I should re do the valve adjustment?. Thank you for your reply.

 

Do you have a vacuum gauge you can connect to the intake? You may be able to identify the problem by how the vacuum needle moves, or what vacuum it's idling at.

 

AB's right, check the vacuum readings. Symptoms sound like a vacuum leak...

 

What AB and BVA said.

 

I used to have a vacuum gauge long time, but I will re adjust all valve as I was unsure if I done the sequence correct last time, I will update you of what the result after the adjustment, thanks you all for the ideas.

 

Adjust the valves, no help, same condition, rough idle, sometime the engine dies, hard starting.
Could it be the Petronix ign that needs the flame thrower 4000???? coil, I used to have one before installed with this electronic ign. I am using a Japanese red color coil, I hope it is at fault.

I have a word on valve adjustment:
I used to adjust the valve each valve at a time, like I adjust all the intake 153624 then I do the exhaust in 12 steps, never had a problem. This time I read in the shop manual Form 7099-66-2 Group 8-10 (this procedure requires two complete turns of crankshaft), that means six turns / six steps ( 1/3 turn for ea set of valves ), doing 2 valves at a time intake and exhaust, I am sure I used to do one valve at a time, lots of work.

 

Check the vacuum and for vac leaks before throwing more $$ at components.

 

Most rough idle posts indicate the air leak or valve sticking is the major problem, I have to get me a vacuum tester before I go any further.

 

I was reading your post , vacuum leak they can be a pain to find. With the engine idling I have used a can of break clean and using the small tube it comes with the can spray a small shot at each intake runner were it meets the head, if it is a gasket leak the engine will smooth out and the RPM will go up. If you don’t detect a gasket leak do the same to the vacuum hoses and connections. Also spray the bottom of the carb. Hope this helps and you find or rule out a leak.

 

Motor_man:

thanks for your hint, is there any alternative to this brake clean in case I don't find it around here, you know some products not common in the middle east market.

 

I'd check the coil. Pertronix suggests 12 volts to the coil/module, divided by the coil's resistance to not exceed 4(amps)? They suggested a 3.0 ohm coil, 12/3ohms=4amps for a 6 cylinder.
Check out their website, they offer installation help, also have a 3.0 ohm coil.
I may be way off base here, but it might be worth checking out.

Another note, not that this applies to your truck, but I've mistakenly reversed the + and- wires on the coil, ran but with similar symptoms that you describe.

Hope you get it sorted, watching for news, good luck!

 

That carburetor cleaner in a spray can works really well too if they don't have brake cleaner.

 

I checked the coil, it is connected correctly, hot wire from bat is connected to positive side of the coil.
Since I don't have a vac tester now, I re tightened both exhaust and intake manifolds bolts to the head, found some loose bolts, start the engine, it ran and idle lots better then before for 10 minutes, turned it off and restart again, now it idle very low and died, start the engine once again it still idles low and if I let the gas pedal off it wont stay long then quits.

I will do the leak test with that carb cleaner, check the plugs gap, check the coil resistance if it is within limit, then I will post the results, I am hoping for some clues that might shorten the way for me.