76 911 runs rough once warmed up
05-31-2003, 10:51 AM
#1
Track Day
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76 911 runs rough once warmed up
I have owned a 76 911 for about a year now, I admit I do drive it quite hard, however until recently I had no problems. Now when I drive it (approx once a week), once it warms up it starts to miss under heavy acceleration.
I drive approx 30 mins with no problems, stop and park for about 1 hour. Then when i drive the same route home again it misses, however if I accelerate gently it will go no problems and reach quite high speeds with only the occasional miss.
I changed the plugs even though the old ones were fine, and I use a premium unleaded fuel.
One other thing if i go for a drive around the area over the top of the mountain and back again (approx 40 min drive)without stopping the car runs like a dream and it gets quite a workout but it does backfire on some downshifts when i double shift ( I dont know if that is related some how).
Any help on this matter would be greatly appreciated before i go forking out a great deal of money to the mechanics for something that may be relatively simple. Thanks. <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" /> <a href="http://www.geocities.com/husam6569/" target="_blank">web page</a>
I drive approx 30 mins with no problems, stop and park for about 1 hour. Then when i drive the same route home again it misses, however if I accelerate gently it will go no problems and reach quite high speeds with only the occasional miss.
I changed the plugs even though the old ones were fine, and I use a premium unleaded fuel.
One other thing if i go for a drive around the area over the top of the mountain and back again (approx 40 min drive)without stopping the car runs like a dream and it gets quite a workout but it does backfire on some downshifts when i double shift ( I dont know if that is related some how).
Any help on this matter would be greatly appreciated before i go forking out a great deal of money to the mechanics for something that may be relatively simple. Thanks. <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" /> <a href="http://www.geocities.com/husam6569/" target="_blank">web page</a>
05-31-2003, 02:48 PM
#2
Burning Brakes
I dont know much about the pre DME engines, but someone will be along with that knowledge.
I had a miss under conditions similar to what youre describing and it turned out to be a bad injector.
I had a miss under conditions similar to what youre describing and it turned out to be a bad injector.
06-01-2003, 10:34 AM
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Husam,
check the easy things first. Points, rotor, cap. I have a '77 and experienced the same. It turned out to be the cd unit, but that may not be the case with you. Also check all your vacuum lines.
Tom
check the easy things first. Points, rotor, cap. I have a '77 and experienced the same. It turned out to be the cd unit, but that may not be the case with you. Also check all your vacuum lines.
Tom
06-01-2003, 12:06 PM
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Husam,
I agree, check points, cap, and rotor. I have a '75 with points, cap, and rotor and find that they need to be changed every couple of years even though I drive the car under 1000 miles a year. Not sure if '76s had changed to electronic ignition yet. Another thing to check would be spark plug wires, unless they are relatively new. Good luck.
Lou
I agree, check points, cap, and rotor. I have a '75 with points, cap, and rotor and find that they need to be changed every couple of years even though I drive the car under 1000 miles a year. Not sure if '76s had changed to electronic ignition yet. Another thing to check would be spark plug wires, unless they are relatively new. Good luck.
Lou
06-01-2003, 12:10 PM
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P.S. Not sure how loud the "backfire" you mention is, but burbling / popping on deceleration, when downshifting, is normal in healthy CIS cars... one of the things that gives the cars character you can't buy at any price in the new ones.
06-02-2003, 06:22 AM
#6
Burning Brakes
UK '76 911s have points, cap and rotor - problem sounds like one of those is at fault; my money is on the rotor, a small item not looked out regularly during servicing.
PJC
PJC
06-15-2003, 09:46 AM
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By vacuum lines do you mean the ones connected to the fuel tank ?
I have noticed that somedays I have experienced difficulty removeing the cap due to intense vacuum pressure.
I have heard this may be the cause of my problems once the car has heated up it has built up a vacuum in the tank.
Does anyone have any experience with this ?
By the way thanks for your replies.......
I have noticed that somedays I have experienced difficulty removeing the cap due to intense vacuum pressure.
I have heard this may be the cause of my problems once the car has heated up it has built up a vacuum in the tank.
Does anyone have any experience with this ?
By the way thanks for your replies.......