Fouling Ignition Rotor

[RJS]

Hi

Beautiful weather in CT this weekend. Trying to the TR out as much as possible. Hope others are too.

Quick question. Twice now in the past 1,000 miles I've experienced a fouling ignition rotor. Symptoms are an engine misfire under load or under more then 1/2 throttle. Symptoms get worse when engine hot, gets better when engine cool.

I can fix it simply by polishing it with a scotch brite pad. When inspecting the rotor after cleaning the edge of the contact is just slightly pitted. I am wondering if this is just a failing rotor which needs replacement or if there is some other condition causing this??

Rotor is about 11 years old with 9,000 miles on it.

Thanks

Bob
PS: I've already ordered a high quality "red" replacement rotor

 

[dklawson]

The physical conditions you are describing on the rotor sound typical to me and don't normally cause running problems. It would not hurt to replace the rotor but I would not expect different performance from its replacement. That being said, you may want to give the engine a more complete tune-up with a new cap, rotor, points, and condenser. I normally wouldn't recommend this as it is sort of a shotgun approach, but you have other ignition parts failing and the rotor may simply be the last straw.

 

[RJS]

One other thought. Could it be "winter" formula gas being run in hot (90s) weather? The tank of gas in there now was filled in late November before I put the car in winter storage. Any chance the winter fuel mix would be more suseptible to percolation/vapor lock in the float bowls?

I definitely saw fuel pumping into the full filter when cranking the motor. So, I'm guessing the float bowls.

Bob

 

[charleyf]

I would include a new coil, distributor cap and plug wires in the shotgun approach. I had similar misfire problems with the engine under load. The first thing that happened to me was that the coil totally died. The car seemed to work good for a while but then again when it was warm (driving over 1/2 hour) and under load going up hill ( elevation climb of several thousand feet) it tended to misfire. A new distributor cap and wires totally cured the problem. So I am guessing the coil may not have been the real problem. Oh, I do have a Crane electronic ignition on the car so it was not a points thing.

Charley Fitch

 

[RJS]

Just as as follow-up. The cap and rotor served me well for 9 years and 9,000 miles. However, after a bit of research, I see that they were cheaper replacements. The cap used aluminum terminals and the rotor was "riveted" and used high carbon black plastic. Apparently, a known issue with these rotors is that the spark will follow the path of least resistance from the rivet, through the spring clip to the distributor shaft. Thus, the misfire. It becomes worse when hot and under load. Exactly my symptoms.

I replaced the cap and rotor with higher quality parts. Cap has brass terminals and the rotor is the red plastic option (not high carbon black plastic) and no rivet. $25 for both.

Engine performs normally again.

Bob

 

[CJD]

There is a chance it's material related, but there is also a possibility oil is coming off the advance assembly and contaminating the inside of the cap/rotor.

 

[DNK]

What brand was the old rotor?

 

[dklawson]

I am glad you got the issue sorted.