dad911sc

My 81' 911 sc surges at any steady throttle setting but not at idle. Not sure what the problem is. Recently overhauled motor, problem became apparent after rebuild. Thanks for any help.

Buffalo

Well, here is a possibility. I recently had to have the cat converter put back on my 82 sc for smogging. My mechanic discovered that the oxygen sensor system was not working, so a new ox sensor was in order.

I noticed a slight surging at slow speeds and a whole lot more sucking air noise. It passed smog non the less.

I put the cat bypass back on, the surging remained.

I took it back to my mechanic with the problem. He promptly unplugged the ox sensor and surging goes away. An air adjustment was in order as well. Sucking air sound goes away. He indicated that unplugging the sensor is ok with a cat bypass. If you have a cat, it could contribute to eventual failure.

He indicated that the ox sensor system is not capable of keeping up with the demands and hense some slight surging.

Powderdog

I have a similar problem but mine is when I am at a stop. The engine will pulsate(surge) with my foot off the throttle. Does not do it all the time maybe more when it is warm. Any ideas what may be causing this or could it be the same as what Dad911sc is experiencing?
Thanks
Steve

Steve Weiner-Rennsport Systems

Gents:

This is not uncommon with these engines;.....its usually a mixture issue.

Before one starts making corrections, one must make sure that everything else is in proper working order:

1) Plugs, cap & rotor

2) Ignition wires

3) No vacuum leaks

4) Injector seals

5) Distributor advance mechanism

6) Clean fuel filter

After you KNOW that all of the above items are perfect, then you can check and adjust fuel mixture as required. SC's with oxysensors tend to run lean when operating in closed loop, and sometimes unplugging the sensor and adjusting the CO to 2.5% makes them run much better, overall.

Speedraser

Steve,

Does unplugging the O2 sensor and setting the CO to 2.5% have any impact on converter life, as mentioned in a previous post?

dad911sc

Thanks guys, I'll check into it and get back to you.

Steve Weiner-Rennsport Systems

Hi Todd:

Yessir, cat-equipped cars should always be operated closed-loop; that is, the oxysensor should always be connected.

Let the ECU control mixture and this will prevent premature cat failures from burnout.

Speedraser

Thanks Steve -- I'll leave well enough alone.