1971 911T misses after changing out CDI

[Jeremy911T]

I have a 1971 911T. Last week it cut out on me. After initially being able to start it and it cut out after a few miles, I was unable to start. I had the CDI and coil bench tested by Bob Aslock (super guy) and the CDI was bad but the coil was good. He was kind enough to loan me a CDI while he rebuilt mine. The CDI he loaned me was an upgraded version with his own electronics that is mainly used for track cars etc. I swapped it out and the car started right away but is missing and idling real low. It was running great prior to the recent issue. I can drive it but need to keep the hand throttle up to keep it going. Is it possible that the new CDI can change the timing or other ignition parameter. Any help would be great!

Jeremy

[356911930]

When was the last time you did a full tuneup? It could also be just the points need cleaning or gapping.

Rahl

[john walker's workshop]

Plugs could be fouled from the initial CD problem. Less than perfect points, carbon tracking inside the distributor cap, etc.

[mysocal911]

Originally Posted by Jeremy911T

I have a 1971 911T. Last week it cut out on me. After initially being able to start it and it cut out after a few miles, I was unable to start. I had the CDI and coil bench tested by Bob Aslock (super guy) and the CDI was bad but the coil was good. He was kind enough to loan me a CDI while he rebuilt mine. The CDI he loaned me was an upgraded version with his own electronics that is mainly used for track cars etc. I swapped it out and the car started right away but is missing and idling real low. It was running great prior to the recent issue. I can drive it but need to keep the hand throttle up to keep it going. Is it possible that the new CDI can change the timing or other ignition parameter. Any help would be great!

Jeremy

It's possible. Use a timing light to check the timing.

[Jeremy911T]

Originally Posted by mysocal911

It's possible. Use a timing light to check the timing.

Thanks. Can you check the timing when the car is missing and not idling correctly. Newbie here. I bought a timing light but have never performed the test before.

[Jeremy911T]

Thank you very much Dave. Can you check the timing when the car is missing and not idling correctly. Newbie here. I bought a timing light but have never performed this test.

[Jeremy911T]

I will definitely check those. Thank you!

[Jeremy911T]

Originally Posted by 356911930

When was the last time you did a full tuneup? It could also be just the points need cleaning or gapping.

Rahl

I will check those things out. Thank you very much!

[fizeus]

if you new CDI has an upgraded electronic board it's possible your timing is off, you should also check carburation because a better spark can now give a lean mixture.

[Jeremy911T]

Thanks. I will check those out.

[T77911S]

swap the coil