first post Misfire help!

[bavarian]

hello just joined but not at all new to m10s and motors ,

 

need help figuring out a misfire this is for a 518i e12 that i dropped a 2.0L into anyway engine has ran over 10,000 miles rebuilt by me , now im getting a misfire that is more noticeable when hot , when hot very noticeable driving midrange cut out  almost clears up ,up top.

32\36carburetor was cleaned  accelerator valve is working haven't checked power valve ,would that affect idle?

 

i dont believe its a carb issue to be honest , i sprayed carb spray no change in idle , dont believe its a vacuum leak either 

 

ok were left with ignition , if i had to describe the feeling it  feels like its one cylinder has a bad spark plug or wire.

new wires new cap new rotor new plugs , 12v at the coil  ,yes coil is the right ohms for the petronix. swapped coils with a new one its not the coil, 

the only thing left is the distributor or petronix, im not too familiar with distributor and petronix failures i checked the dizzy and there's quite a bit of play up and down but not so much from side to side. everything else looked normal , have to say i feel like the new rotor is already worn a bit at the tip  on one side more then the other ?

 

it gets worse when hot it almost like intermittent at idle but is almost underivable keep cutting out when its really hot , i wonder... it might just have to be a bad distributor or petronix , 

 

thanks for any help much appreciated 

[stephers]

There has been many noted issues with Pertronix systems when getting hot or after a driving for a bit, they start to cut out   If you still have your old points and condensor set up, I would pop those back in, not worry about the coil voltage, you won't be running them long enough to burn out a set of points and if you do, so what, this is just for elimination process

 

Thanks, Rick

[John76]

2 hours ago, bavarian said:

there's quite a bit of play up and down

Shim the distributor shaft and replace the fiber washer and O-ring.

A hot engine can pump thin oil into the dizzy and foul the PerTronix if the shaft has excessive axial play.

[TobyB]

Use an inductive timing light on each plug when it's misfiring.  

If it's not getting spark, the light won't flash.  

 

t

[VWScott]

Test light on neg side and ground to body,spin the engine over via wrench at crank. It should light at every cylinder or when the points close

[Dudeland]

Pertronix is kinda sus in that case.