Ignition Timing Question

coltarms · Post by **coltarms** » Fri Mar 31, 2006 10:28 am

When I set my ingition timing, I notice that it seems to "skip" every few rotations. The timing light shows the crank at 5 deg BTDC, but every few rotations I do not see the timing notch. Is this normal? Performance-wise, I am still only getting 19mpg and the accelleration seems to have gotten it's stumbles and flat spots back. Having the timing at 7' btdc made it ping at about 3500-4000rpm, but it sure ran better.... Compression was at 155psi all cylinders. Plugs looked clean when I checked 'em a month ago. Wires are new. Distrib cap and rotor were new in September and I just cleaned the electrodes last weekend (they got wet.)

Any one else ever see this?

shogun · Post by **shogun** » Fri Mar 31, 2006 10:47 am

i use 95 octane gas and allways run 12btdc, and i dont have any trouble

takza · Post by **takza** » Sat Apr 01, 2006 2:33 am

Have you checked the gas level in the carb...thru the sight glass in front?

coltarms · Post by **coltarms** » Sat Apr 01, 2006 10:38 pm

gas level is right in the middle where the manual says it should be....

takza · Post by **takza** » Sun Apr 02, 2006 5:46 am

I suspect either ignition or fuel problems.

But seriously folks.....could be a bad dist...could be the carb needs rebuilding....more likely it's the vacuum advance on the dist????

Typrus · Post by **Typrus** » Sun Apr 02, 2006 4:44 pm

Get both advances on the dist checked.
Check all spark leads for breaks and resistance.
Check all spark plugs for proper gap and no fouling.

Might still be wet in places?

Mine did the same, got better if it was advanced, but would ping.
Engine would leave me stranded at random.

Turned out to be a carb in desperate need of a rebuild. My float bowl read correctly as well. Had it rebuilt and it was a different car altogether. Went from 15-19mpg to 21-28 instantly.

Chris · Post by **Chris** » Wed Apr 05, 2006 5:41 pm

If you're not seeing the timing notch every few revolutions I would say that the timing light is not firing. Now the cause of that could be a faulty timing light or the spark plug is not firing. With a lean or rich mixture and the plug in good shape, the plug should fire. It might not ignite the mixture but it should still fire. Vacuum advance diaphram problems will give you poor mileage/performance but should still fire the plug. Try hooking the timing light to #4 cylinder wire. It should give you the same pattern on the timing mark.

Does the engine idle smoothly or does it sound like it misfires every few revolutions? With the engine idling try pulling off one spark plug wire at a time and see if you get equal RPM drop with each cylinder.

As far as poor mileage...check the EGR and EVAP systems as well. Also look for some of the more overlooked items...low tire inflation or dragging brakes. I realize that each one alone would not give you the poor mileage that you are experiencing but it could be an accumulative effect.

I wonder if the power valve in the carb is stuck on all the time.

Disconnect the vacuum advance lines and plug them....then check the mechanical advance with the timing light.

Don't know if this helps you any?