1970 911 s pop on decel

[denson]

The car runs great, but after a 50 mile ride today, she popped real loud on two separate occasions. The car never does this, so is this a sign something is up, or does this just happen sometimes? Maybe gas related, or is it time to call Gus Phister?

Thanks,

John

[Flieger]

Do you have the speed switch (rpm transducer fuel shutoff on overrun) enabled?

[denson]

Ok, so far so good. I took the S out today for another 50 miles. No pops today! Thank God, MFI can be a bit tough sometimes.

[boxster03]

If the MFI is dialed in and the micro switch cut off is working then your throttle bodies might be starting to wear. How is your idle ?

[denson]

Funny that you ask that. The idle seems a touch lower than is normal. As a matter of fact when going into neutral after higher revs, I found the red battery light came on, but went off once I gave the car a bit of gas.

Hmmm!

Any thoughts?

John

[edmayo]

When was the point gap and ignition timing last checked?

[Flieger]

Do you have the speed switch (rpm transducer fuel shutoff on overrun) enabled?

You haven't answered this question. Backfiring out the exhaust on overrun is the speed switch either not being hooked up or being broken.

[denson]

I wish I could answer this question. I need my mechanic to look at this as I am not good in this area. car is going in tonight if it does not rain. Once I know the problem, I will post it.

[Mr9146]

You haven't answered this question. Backfiring out the exhaust on overrun is the speed switch either not being hooked up or being broken.

That is a definitive statement and while it MAY be the case, it IS NOT the only reason for backfiring. You need to work in generalities, Mr. Engineer.

I tend to agree with Ed that the points may need to be adjusted, but it's tough to diagnose this kind of thing over the internet.