doo

still working to get the 928 running well again after previous owner had it out of commission for 2 years. lots of new parts. Now have it back to starting up easily, idling well and can move it around under low load no problem, even spin some gravels with take off. when moving along at any speed 10-20 mph and try to hard accelerate it will bog down/hesitate and nearly die. let off pedal and engine comes back alive but not able to accelerate or rev high while in gear. while in park and idling it can be revved up to 4000 + easily and no bog down. it is automatic with CIS injection. What are the symptoms of control pressure being too low or too high? Any help greatly appreciated.

Daniel5691

Hi !

Here's a great starter reference for the good ol' CIS ....

http://928classics.com/4/post/2014/0...ide-78-79.html

GlenL

So many things can be wrong besides the control pressure. Most likely there's varnish or just gunk in the system. One thing you should NOTdo is try to adjust control pressure or mixture to compensate for that. You'll never get it right and as the problems get worse, or get better, it'll run poorly.

What new parts are in the car? What tests have you done?

My first suggestion is to make sure the gas is fresh and put some Seafoam in the tank. Then drive it as best as it can be. It may clean itself out and run well. That'd be a usual pattern for CIS cars that have sat.

doo

Rebuilt fuel distributor, rebuilt and adjustable WUR, new cap, new rotor, new green wire, new coil, new wires, new plugs, cleaned all fuel lines, cleaned all injectors. dropped tank and cleaned, new strainer, new fuel pump, new filter, cleaned main fuel line and return line. removed and cleaned plenum and intakes, new couplers, new gaskets at intakes and air meter box, new vacuum lines (silicone).
I just got other gauge this week and am getting ready to see what the control pressure really is on current settings of WUR, etc. also ordered the Colortune stuff for each side and will be in by end of week to help adjust things I hope..... I do have some suspicion of alternator not performing well also....

James Bailey

Your car will run just fine on a fully charged battery for at least 1/2 and hour with no alternator at all...so not part of your problem.

GlenL

Impressive. Most impressive.

You're ready for control pressure tests. Did you get the POS Harbor Freight gauge by any chance?

Low control pressure will make it run rich. My experience is that it won't idle and stinks. After starting it needs to be revved to keep running. I've never had a too-high control pressure issue.

doo

got the gauges, removed the shraeder valves and they work great. control was too low at 10..... needle in the WUR had gotten out of place. readjusted it and reinstalled now I have correct control pressures. I have color tune installed now and ready to restart and finish tuning it out. hopefully got the AF issue done and will soon move toward upgrading ignition to the MSD 6AL.

GlenL

Nice. I've had driveability problems due to WUR rattle. "Rattle?" The pin wasn't seated in the cups and was just bouncing around.

Why the MSD system?

doo

the MSD has a multiple spark for better overall combustion with ability to advance or retard without moving distributor. I've read good things about it in all vehicles. the few porsches ones I have read about gave high praises about idle smoothness, easy start, more power, less trouble with rich mix.