engine and drivetrain Ignition Troubles

[pinkey]

So my 2002 has a rebuilt engine with tii piano top pistons, weber 38/38 downdraft, 320i headers among other goodies.  I kept my 008 tii mechanical advance dizzy from my old engine and put it in my fresh engine. the problem is if my cap or rotor have the smallest amount of residue from use it begins to misfire and even start to cut out when I hit the gas. If i clean my rotor with a little sandpaper or steel wool and clean the terminals on the inside of the cap with a wire wheel on a Dremel it runs fine again, for about 15 minutes to an hour. Then after some build up it begins to miss again. timing is spot on, spark plugs are brand new (old ones looked fine) the points are new and properly gapped, the cap and rotor are older but obviously I keep them spotless, the condenser is a year or so old, and the wires are about 3 years old, (to the car) they are the old school kind with actual metal wires inside, not the modern style that have the weird fiberglass looking stuff. After inspecting the cap I noticed that sometimes the spark will arc to the side of the terminals in the cap (probably the cause of cutting out when I step on the gas) I plan on replacing cap, wires? and condenser very soon. do you think my dizzy needs a rebuild? or replacement? what about the dwell angle? (never checked) also FWIW I have tried a few different rotors I have and measured the resistance it seems the higher the resistance rotor the better it runs.  Any guidance would be much appreciated! TIA!

 

Bosch rotor with small amount of residue 

 

another shot of the rotor 

 

Bosch cap with residue and arc marks to the sides of the terminals

 

another view of the terminals on the cap

 

my tii 008 dizzy with rotor removed 

 

and an engine bay shot just for fun

[peterschop]

Sounds to me like you need a new cap, rotor and condenser. Arcing in cap makes me think it may have a stress crack that you can not see even though it looks good. That could cause your misfire. Your year old condenser could be bad, replace it. Go easy with the Dremel on the cap as you don't want to remove too much material. Just use a piece of sandpaper or emery cloth. If you can't clean it up with that, replace.  The contacts in your cap don't look good to me.

 

Dwell angle changes with the point gap adjustment. If your points are set right, the dwell angle should be right. You should be able to find a dwell-tack-volt meter for pretty cheap. I replaced my 40 year old one with one on Amazon. (Old one still works fine.)

 

Is your distributor bad? Don't know without more information. With cap off, grab the rotor and gently turn. It should have movement in one direction and then spring back by itself. If not, you mechanical advance is not working. Next remove the rotor to check the shaft wear. Try moving the shaft back and forth for horizontal play, there should be very little. A little up and down movement is ok. If you do have shaft wear, a Pertronix or Crain unit will take care of it. Then you won't have to worry about setting the points or checking the dwell.

[ray_]

What coil (and ballast, if any) are u running? Same as prior?

 

But yeah, do what Peter said.

 

Cheers,

[Hans]

Some faint bell ringing on this problem: condenser.

[Mike Self]

Another suspect:  you have engine oil leaking up the distributor shaft into the points area.  The oil mist settles on everything, and when the brass contacts and the points arc while transferring the high voltage spark, the oil residue is burned, thus fouling those contacts.  

 

Take some carb cleaner and carefully clean the inside of the cap and the rotor's surface with a clean paper towel; see if the towel is dirty when you're finished.  Then drive for awhile--until it starts misfiring again--and clean again.  If the towel is dirty the second time, it may be time to do a little dizzy rebuilding as you have sufficient clearance between shaft and bushings to allow oil where it shouldn't be.  I think shaft bushings may still be available from Bosch if you want to do it yourself, or you can send your dizzy out for a rebuild.  See archives for suggestions on rebuilding.  Shoud you choose the latter, you can have the advance curve customized for your rebuild.

 

cheers

mike

[jireland2002]

Check the shaft on the dist.  If you can wiggle it side to side it may be part of the problem. 

Your problem may be a time/temperature issue.  When the engine is running poorly check the coil.  If it is too hot to hold onto it is probably bad. 

It certainly would not hurt to replace the points and condenser.

If there is not something really obviously wrong I always check the timing before any thing else.

[pinkey]

Thanks to everyone who replied! I replaced the condenser, cap, rotor, and points (again) checked the resistance on the wires and all were well within spec.  also some of the wires going to the positive lead on the coil (electric fuel pump) (electric choke) were touching the engine bay. I rotated the coil and adjusted the wires so nothing was touching the side of the bay.  I also tightened the screw that holds the coil and ballast resistor. after all that its running like a champ.  idk what it was but a full replacement seemed to do the trick.  the mechanical adavance on the dizzy is working and not much play side to side either.  no oil that I can see In the dizzy.   Thanks again to all of you who took the time to reply with your wizdom