car runs poor during warmup 73 cis with 80 3.0
 

ok guys i have spent many hours searching for the cause of this problem. heres the short version.

1. this is a 73 911t with a 1980 3.0 the car came to me not running the air box had split its seam. so i removed air box drilled all screw holes to number 10 and installed stainless screws and epoxied seam back together. installed pop-off valve.
2. before running car i check cold cp and found it at system pressure 4.9 bar. since i have a few WURs laying around i found a match and installed it set system pressures to spec 1.7 cold and 3.1 hot. set the CO to 3% seems to be the sweet spot for this car. checked the timing and plugs during all this as well all in good shape.holds fuel pressure overnight.

3. car starts and runs great cold warms up and runs great hot. ok heres the problem if you try to drive car during warm up it hesitates and bucks a bit and is not smooth like my other two cis cars. after warm up it runs great starts great hot.

the aav is working well and is in time with the wur. have checked for vacuum leaks hot and there is none THAT I CAN FIND. idle is stable hot and drops to 900 without any surging. if anyone has any ideas please let me know. or should i just be happy it runs so well hot and cold starts with just a touch of the key and raises up to 1800 rpms for about 60 sec. and then slowly drops to its 900.

cheers ed

Ecu.......
 

Carrera Turbo,

Did the previous owner include the ECU (electronic control unit) in the installation? Except for the earlier SC's ('78-'79), the later SC models '80-'83 utilize ECU for the oxygen sensor system. They have frequency valves not available in the earlier SC's. Keep us posted.

Tony

My chart shows for an 80, 1.7 cold @ 10C is correct, but warm and running should be 3.4 to 3.8.http://forums.pelicanparts.com/uploa...1248287300.jpg

See the bottom chart and graph. Ignore the handwritten notes.

Have you tried the other usuals, incl ignition parts: wires, cap and rotor? How about the dizzy?

My car started bucking and hesitating the other day. Turned out to be a bad connection from the CDI to the coil.

thanks guys

well the car has no ecu and no frequency valve. the car has the 045 WUR and i set the control pressures according to the 045 WUR. this is the WUR that was on this car and i assumed someone has removed all the ecu components and has been running it as if it where a 78-79 motor.
so is it safe to say that my pressure hot is to low. wouldn't the car run poorly hot? it runs very well hot and only hesitates bucks during the warm up cycle.

there is no popping threw the intake just surging until hot. i removed the vacuum advance and tried running it plugged there was really no difference that i could tell.

this car has no cat or O2 sensor has SSIs and standard 74 style dansk muffler.

cheers ed