[Miklo II]

recently copped a '75 SDV, 57,xxx miles, bought it from original owner.
Ive been told the car sat for the last 3 - 5 years. Replaced fuel pump and had Q Jet partially dismantled for internal cleaning. New spark plug wires and distributor cap. Coil was not replaced. Car ran rough for awhile. Slight misfire sometimes stall at idle, would bog/stumble at light throttle and doesnt like to drive above 50 mph. backfired here and there when let off throttle. i put Marvel Mystery oil in tank and crankcase, removed stuck heat riser altogether. The backfiring and idle issues completely stopped.

Still had the slight misfire at idle and the bog at light throttle. Replaced rusty gas tank with one out of a '74 fleetwood (which was used 2 weeks prior and still very shiny inside). Rust particles and unknown "dirt/sediment" with the other dirty tank had clogged external fuel filter and starved the engine making her backfire worse. I put Seafoam in the replacement tank and she ran good for 20 min. Again more backfiring and starving for fuel. This happens in any gear in "D". When I drop to nuetral it idles fine. I can floor it and no hesitation.

What to do, what to do? keep in mind ive had this car 2 months now.

 

[csbuckn]

Stuck advance on the distributor? Vacuum advance not working?

 

[Jbmoffo]

Not sure about misfire, but have you checked for vacuum leaks. They often cause the bog at light throttle that you are mentioning. By the way, you did not mention if the car does this with a cold engine.....

 

[drmenard]

I would check the spark.. See if it looks weak.. Could be the coil is starting to go bad..With a bad coil the hotter it gets the worse it gets..

 

[Miklo II]

No engine does all this when warmed up. As for outside weather, she likes to misfire when its below 70 degrees.
Keep in mind the exhaust is an open Y pipe (thats how it was when I bought it), ends right under the passenger front pass. side.

 

[Miklo II]

UPDATE: Replaced coil and has run good. Still has bog at any throttle (light or full). Have to put pedal midway for a quik second then release as the car rolls and midway again and then it "clears its throat" and has perfect acceleration after. This always happens from a DEAD stop. If im rollin above 15 mph it will accel fine. What would make it run so choppy? And i seem to have the same choppiness with pedal to the floor over 50 mph. ??????

 

[Jbmoffo]

Vacuum leak OR accelerator pump in carb needs replacement.

 

[Fleetwood472]

Seems like the advance weights are sticking in the distributor. Happened to me before with very similar symptoms. I'd open up the distributor and clean it I p. Or you could just replace it with a completely rebuilt distributor. They're pretty cheap now days. Could also be a bad egr valve or an issue with not enough back pressure due to your exhaust setup.

 

[Jeff R]

57K or 157K? Any chance she jumped time?
Jeff

 

[drmenard]

The cam gear has plastic coating on the stock gear.. After this many years it can crack and break off causing way too much slop and can jump timing.. But on 74-76 motors , they all have large chamber heads, the pistons will not hit the valves if it jumps time.. The cheap timing sets, $30-$40 are no good and I suggest not to use them. Do it once and use a Cloyes single roller chain and sprockets that can be bought for $80 to $175.. The $80 is perfect for a stock motor ..

 

[Jeff R]

Running points?? If so, i would like for you to replace the condenser. An old one will do if you have one in your toobox. Worth a try-----I just had a bad condenser with mine.

 

[Miklo II]

57K or 157K? Any chance she jumped time?
Jeff

59K original. Im second owner.

Running points?? If so, i would like for you to replace the condenser. An old one will do if you have one in your toobox. Worth a try-----I just had a bad condenser with mine.

Nope, running HEI.

UPDATE:
Replaced carb today with another Q-jet off of '89 454 out of an RV. Had to use 1" spacer since throttle lever is for the 700r4 TV cable and wont clear the "low rise" factory intake. idle mix screws are non existant. It nearly dies after light throttle in Park. Give it more gas and stays alive, NO BOG,HESITATION OR BACKFIRE (FINALLY !!) Put it in reverse or forward gear and after 3 seconds it stalls completely. But if I give it mid throttle it drives with no problems whatsoever. uhhh :hmm:

 

[Miklo II]

Problem solved! Idle too low, turned up a few notches and runs great!