Engine surge at steady throttle
#1
2nd Gear
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Join Date: Aug 2003
Location: morgantown, WV
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Engine surge at steady throttle
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.
#2
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Join Date: Aug 2001
Location: Newman, California
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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.
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.
#3
surging at idle
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
Thanks
Steve
#4
RL Technical Advisor
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.
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.
#7
RL Technical Advisor
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.
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.