engine and drivetrain Advice on Stuttering Issue

[Buckeye]

I will greatly appreciate advice to what it could be probable cause(s) for the car stutter / jerking while driving at constant speed (40 – 70 mph) in 3rd or 4th gear.

The car idles fine, no stutter issue when under load (speeding up) and there is no lack of power in any gears or speed.

The car equipped with 32/36 DGAV (water choke) and odometer is @ 91K (actual) miles.

Should note that recently had to replace original cylinder head (E21 2.0, 76) due to severe cracks in chamber No. 2 & 3 with a similar cylinder head (E21 2.0, 78). Replacement cylinder head was checked, machined and refurbished at a reputable local shop.

During cylinder head replacement process, replaced crankshaft front & rear seals along with new clutch, pressure plate, pilot bearing and throw-out bearing (flywheel flatness checked ok, therefore there was no need for re-surfacing).

New spark plugs, point, condenser and coil were installed before engine start up. Did not change original spark plug wires since did not see any signs of deterioration.

The car was tuned up to following specs:

Point gap to 0.016”

Point dwell - 50º (dwell meter reading)

Timing @ 25º BTDC at 1,400 RPM

I realize point dwell is below factory range (59º - 64º) and admit that it is more important than factory point gap spec, but have not had time to correct it yet and not sure if it could be one of the contributors to current stutter issue.

I have included a lot of information here that may or may not contribute to stutter issue, but thought it is important to provide recent car history.

Thanks.

[c.d.iesel]

the distributor mechanical advance plate is fuched-up (?)

use yer timing light to watch the movement of the

timing marks as you gradually increase rpms - slowly-

the marks should not be bouncing irraticly or jumping

or holding locked on during rpm changes.

[Buckeye]

the distributor mechanical advance plate is fuched-up (?)

use yer timing light to watch the movement of the

timing marks as you gradually increase rpms - slowly-

the marks should not be bouncing irraticly or jumping

or holding locked on during rpm changes.

I recall timing mark was bouncing in both directions to reference line at 1400 RPM. But did not know what was causing that.

Is there any other ways to check/ test distributor mech. Adv. plate so it can be confirmed it is the culprit.

Do I need to replace the hole unit or can I just replace some components?

Thanks.

[dlhoovler]

Try this: http://www.imdb.com/title/tt1504320/

-Dave

[dlhoovler]

Sorry! Couldn't resist. A far as the distributor advance plate goes, as of a few years ago, you could still buy the whole plate assembly from BMW. That may have been the vacuum advance plate, though. For mechanical, you may need to get a good used distributor or send yours out to be rebuilt. I can't help much with the diagnosis, though.

-Dave

[Buckeye]

Try this: http://www.imdb.com/title/tt1504320/

-Dave

[dlhoovler]

Stuttering... "The King's Speech"...

Sorry; poor attempt at humor.

-Dave

[Buckeye]

the distributor mechanical advance plate is fuched-up (?)

use yer timing light to watch the movement of the

timing marks as you gradually increase rpms - slowly-

the marks should not be bouncing irraticly or jumping

or holding locked on during rpm changes.

Took distributor cap off and tried to wiggle the shaft. No play in the shaft. Rotated rotor clockwise and it rotated back when let go of it. Checked vacuum regulator and seems functioning ok.

Not sure what is missing? Is it possible this is carburator problem?

[c.d.iesel]

should've mentioned it also - remove the cap again

and now examine the condition of the 4-cam lobes

Any scoring, grooves, ramp wear causes by years and 1000's

of miles without proper cam lube

that's another cause for the irratic behavior

of the timing marks.

you need a new distributor if the cam lobes are f_ _ ked

the condition of firing order of each cylinder around

the degrees of engine rotation is probably the least

recognized cause for an engines loss of power, smoothness,

general running health. people just don't know that it

exists!

cylinder degree firing and ignition timing must be correct

before any fuel system adjustments are made.

also go back and adjust for 59* dwell - reset the timing

at 1,400 rpm with what you've got for now

do a site search for distributor rebuilding service.

these people have old school distributor test

bench to test the cylinder firing degrees and mechanical

advance function/curve. don't sweat the advance curve stuff.

It's the cylinder firing deegress that matters most. both matter.

[Buckeye]

Thanks C.D. For valuable advise. PROBLEM SOLVED.

Took distributor contact breaker plate out, cleaned and lubed. Examined and cleaned coil springs, weights, etc. lube and re-assembled. Also checked the run-out, no problem there. Set the dwell angle to 60* re-timed the engine. RUNS GREAT.